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• Jquery live() vs delegate()

  - by PeeHaa

  I've read some posts here and on the web about the differences of live() and delegate(). However I haven't found the answer I'm looking for (if this is a dupe please tell me). I know the difference between live and delegate is that live can not be used in a chain. As I also read somewhere delegate is in some case faster (better performance). So I am wondering is there a situation where you would use live instead of delegate?

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• create a readonly connection to MySQL?

  - by acidzombie24

  I looked at the MySql Connection Options and it doesnt seem to be there. Is there a way to create a read only connection/command for .NET? With SQLite i could specify read only=true to do this. What can i do with MySQL?

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• Reading data from USB using C#?

  - by SamGMU

  I do not want to read serial port nor other possible easy shortcuts please. I would like to know how to read a USB port in my laptop using C#. whether you can suggest a site or explain the flow of the process i will greatly appreciate your help

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• Windows Phone 7 development: reading RSS feeds

  - by DigiMortal

  One limitation on Windows Phone 7 is related to System.Net namespace classes. There is no convenient way to read data from web. There is no WebClient class. There is no GetResponse() method – we have to do it all asynchronously because compact framework has limited set of classes we can use in our applications to communicate with internet. In this posting I will show you how to read RSS-feeds on Windows Phone 7. NB! This is my draft code and it may contain some design flaws and some questionable solutions. This code is intended to use as test-drive for Windows Phone 7 CTP developer tools and I don’t suppose you are going to use this code in production environment. Current state of my RSS-reader Currently my RSS-reader for Windows Phone 7 is very simple, primitive and uses almost all defaults that come out-of-box with Windows Phone 7 CTP developer tools. My first goal before going on with nicer user interface design was making RSS-reading work because instead of convenient classes from .NET Framework we have to use very limited classes from .NET Framework CE. This is why I took the reading of RSS-feeds as my first task. There are currently more things to solve regarding user-interface. As I am pretty new to all this Silverlight stuff I am not very sure if I can modify default controls easily or should I write my own controls that have better look and that work faster. The image on right shows you how my RSS-reader looks like right now. Upper side of screen is filled with list that shows headlines from this blog. The bottom part of screen is used to show description of selected posting. You can click on the image to see it in original size. In my next posting I will show you some improvements of my RSS-reader user interface that make it look nicer. But currently it is nice enough to make sure that RSS-feeds are read correctly. FeedItem class As this is most straight-forward part of the following code I will show you RSS-feed items class first. I think we have to stop on it because it is simple one. public class FeedItem {     public string Title { get; set; }     public string Description { get; set; }     public DateTime PublishDate { get; set; }     public List<string> Categories { get; set; }     public string Link { get; set; }       public FeedItem()     {         Categories = new List<string>();     } } RssClient RssClient takes feed URL and when asked it loads all items from feed and gives them back to caller through ItemsReceived event. Why it works this way? Because we can make responses only using asynchronous methods. I will show you in next section how to use this class. Although the code here is not very good but it works like expected. I will refactor this code later because it needs some more efforts and investigating. But let’s hope I find excellent solution. :) public class RssClient {     private readonly string _rssUrl;       public delegate void ItemsReceivedDelegate(RssClient client, IList<FeedItem> items);     public event ItemsReceivedDelegate ItemsReceived;       public RssClient(string rssUrl)     {         _rssUrl = rssUrl;     }       public void LoadItems()     {         var request = (HttpWebRequest)WebRequest.Create(_rssUrl);         var result = (IAsyncResult)request.BeginGetResponse(ResponseCallback, request);     }       void ResponseCallback(IAsyncResult result)     {         var request = (HttpWebRequest)result.AsyncState;         var response = request.EndGetResponse(result);           var stream = response.GetResponseStream();         var reader = XmlReader.Create(stream);         var items = new List<FeedItem>(50);           FeedItem item = null;         var pointerMoved = false;           while (!reader.EOF)         {             if (pointerMoved)             {                 pointerMoved = false;             }             else             {                 if (!reader.Read())                     break;             }               var nodeName = reader.Name;             var nodeType = reader.NodeType;               if (nodeName == "item")             {                 if (nodeType == XmlNodeType.Element)                     item = new FeedItem();                 else if (nodeType == XmlNodeType.EndElement)                     if (item != null)                     {                         items.Add(item);                         item = null;                     }                   continue;             }               if (nodeType != XmlNodeType.Element)                 continue;               if (item == null)                 continue;               reader.MoveToContent();             var nodeValue = reader.ReadElementContentAsString();             // we just moved internal pointer             pointerMoved = true;               if (nodeName == "title")                 item.Title = nodeValue;             else if (nodeName == "description")                 item.Description =  Regex.Replace(nodeValue,@"<(.|\n)*?>",string.Empty);             else if (nodeName == "feedburner:origLink")                 item.Link = nodeValue;             else if (nodeName == "pubDate")             {                 if (!string.IsNullOrEmpty(nodeValue))                     item.PublishDate = DateTime.Parse(nodeValue);             }             else if (nodeName == "category")                 item.Categories.Add(nodeValue);         }           if (ItemsReceived != null)             ItemsReceived(this, items);     } } This method is pretty long but it works. Now let’s try to use it in Windows Phone 7 application. Using RssClient And this is the fragment of code behing the main page of my application start screen. You can see how RssClient is initialized and how items are bound to list that shows them. public MainPage() {     InitializeComponent();       SupportedOrientations = SupportedPageOrientation.Portrait | SupportedPageOrientation.Landscape;     listBox1.Width = Width;       var rssClient = new RssClient("http://feedproxy.google.com/gunnarpeipman");     rssClient.ItemsReceived += new RssClient.ItemsReceivedDelegate(rssClient_ItemsReceived);     rssClient.LoadItems(); }   void rssClient_ItemsReceived(RssClient client, IList<FeedItem> items) {     Dispatcher.BeginInvoke(delegate()     {         listBox1.ItemsSource = items;     });            } Conclusion As you can see it was not very hard task to read RSS-feed and populate list with feed entries. Although we are not able to use more powerful classes that are part of full version on .NET Framework we can still live with limited set of classes that .NET Framework CE provides.

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• How to setup linux permissions for the WWW folder?

  - by Xeoncross

  Updated Summery The /var/www directory is owned by root:root which means that no one can use it and it's entirely useless. Since we all want a web server that actually works (and no-one should be logging in as "root"), then we need to fix this. Only two entities need access. PHP/Perl/Ruby/Python all need access to the folders and files since they create many of them (i.e. /uploads/). These scripting languages should be running under nginx or apache (or even some other thing like FastCGI for PHP). The developers How do they get access? I know that someone, somewhere has done this before. With however-many billions of websites out there you would think that there would be more information on this topic. I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions. What permissions are need to be used on /var/www so that... Source control like git or svn Users in a group like "websites" (or even added to "www-data") Servers like apache or lighthttpd And PHP/Perl/Ruby can all read, create, and run files (and directories) there? If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www...? Therefore, it seems like the correct permission would be chmod -R 1660 which would make all files shareable by these four entities all files non-executable by mistake block everyone else from the directory entirely set the permission mode to "sticky" for all future files Is this correct? Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be. Update 2: The folder structure of /var/www changes drastically as one of the four entities above are always adding (and sometimes removing) folders and sub folders many levels deep. They also create and remove files that the other 3 entities might need read/write access to. Therefore, the permissions need to do the four things above for both files and directories. Since non of them should need execute permission (see question about ruby/php above) I would assume that rw-rw-r-- permission would be all that is needed and completely safe since these four entities are run by trusted personal (see #2) and all other users on the system only have read access. Update 3: This is for personal development machines and private company servers. No random "web customers" like a shared host. Update 4: This article by slicehost seems to be the best at explaining what is needed to setup permissions for your www folder. However, I'm not sure what user or group apache/nginx with PHP OR svn/git run as and how to change them. Update 5: I have (I think) finally found a way to get this all to work (answer below). However, I don't know if this is the correct and SECURE way to do this. Therefore I have started a bounty. The person that has the best method of securing and managing the www directory wins.

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• stunnel crashing

  - by Jay

  I'm trying to use stunnel to secure a legacy application's communications. I can't seem to get it setup and working. Can anyone provide any hints where I'm going wrong? Here's what I'm trying to accomplish: A windows service on a client machine connects to a server on port 7000 using TCP. I'd like to encrypt the communication between client and server. Here's what I've tried: Created a new server that accepts ssl connections on port 7443. Got a certificate for the server and installed it. That seems to work with my test setup. Installed stunnel on my windows machine (version 7.43 from the distribution archive file). Installed libssl32.dll and libeay32.dll in the same directory as stunnel.exe ( from the openssl-0.9.8h-1 binary distribution). Installed it as a service using "stunnel -install" Configured stunnel as follows: debug=7 output=C:\p4\internal\Utility\Proxy\proxy.log service=Proxy taskbar=no [exchange] accept=7000 client=yes connect=proxy.blah.com:7443 I changed my hosts file to trick the old application into connecting through stunnel: server.blah.com 127.0.0.1 # when client looks up server it goes to stunnel proxy.blah.com IP-address-of-server.blah.com # stunnel connects to new server "server.blah.com" now resolves to the machine it's running on (i.e. stunnel). "proxy.blah.com" goes to the real server. stunnel should connect to the server. I start the stunnel service and try to connect. It looks like it's working but the stunnel service just shuts down with no message. 2010.04.19 13:16:21 LOG5[4924:3716]: stunnel 4.33 on x86-pc-mingw32-gnu with OpenSSL 0.9.8h 28 May 2008 2010.04.19 13:16:21 LOG5[4924:3716]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 2010.04.19 13:16:49 LOG5[4924:3748]: Service exchange accepted connection from 127.0.0.1:4134 2010.04.19 13:16:49 LOG6[4924:3748]: connect_blocking: connecting x.80.60.32:7443 2010.04.19 13:16:49 LOG5[4924:3748]: connect_blocking: connected x.80.60.32:7443 2010.04.19 13:16:49 LOG5[4924:3748]: Service exchange connected remote server from x.253.120.19:4135 2010.04.19 13:20:24 LOG5[3668:3856]: Reading configuration from file stunnel.conf 2010.04.19 13:20:24 LOG7[3668:3856]: Snagged 64 random bytes from C:/.rnd 2010.04.19 13:20:24 LOG7[3668:3856]: Wrote 1024 new random bytes to C:/.rnd 2010.04.19 13:20:24 LOG7[3668:3856]: RAND_status claims sufficient entropy for the PRNG 2010.04.19 13:20:24 LOG7[3668:3856]: PRNG seeded successfully 2010.04.19 13:20:24 LOG7[3668:3856]: SSL context initialized for service exchange 2010.04.19 13:20:24 LOG5[3668:3856]: Configuration successful 2010.04.19 13:20:24 LOG5[3668:3856]: No limit detected for the number of clients 2010.04.19 13:20:24 LOG7[3668:3856]: FD=312 in non-blocking mode 2010.04.19 13:20:24 LOG7[3668:3856]: Option SO_REUSEADDR set on accept socket 2010.04.19 13:20:24 LOG7[3668:3856]: Service exchange bound to 0.0.0.0:7000 2010.04.19 13:20:24 LOG7[3668:3856]: Service exchange opened FD=312 2010.04.19 13:20:24 LOG5[3668:3856]: stunnel 4.33 on x86-pc-mingw32-gnu with OpenSSL 0.9.8h 28 May 2008 2010.04.19 13:20:24 LOG5[3668:3856]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 2010.04.19 13:21:02 LOG7[3668:4556]: Service exchange accepted FD=372 from 127.0.0.1:4156 2010.04.19 13:21:02 LOG7[3668:4556]: Creating a new thread 2010.04.19 13:21:02 LOG7[3668:4556]: New thread created 2010.04.19 13:21:02 LOG7[3668:3756]: Service exchange started 2010.04.19 13:21:02 LOG7[3668:3756]: FD=372 in non-blocking mode 2010.04.19 13:21:02 LOG5[3668:3756]: Service exchange accepted connection from 127.0.0.1:4156 2010.04.19 13:21:02 LOG7[3668:3756]: FD=396 in non-blocking mode 2010.04.19 13:21:02 LOG6[3668:3756]: connect_blocking: connecting x.80.60.32:7443 2010.04.19 13:21:02 LOG7[3668:3756]: connect_blocking: s_poll_wait x.80.60.32:7443: waiting 10 seconds 2010.04.19 13:21:02 LOG5[3668:3756]: connect_blocking: connected x.80.60.32:7443 2010.04.19 13:21:02 LOG5[3668:3756]: Service exchange connected remote server from x.253.120.19:4157 2010.04.19 13:21:02 LOG7[3668:3756]: Remote FD=396 initialized 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): before/connect initialization 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write client hello A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server hello A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server certificate A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server done A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write client key exchange A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write change cipher spec A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write finished A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 flush data 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read finished A The client thinks the connection is closed: No connection could be made because the target machine actively refused it 127.0.0.1:7000 at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.Sockets.Socket.Connect(EndPoint remoteEP) at Service.ConnUtility.Connect() Any suggestions?

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• Increase samba space on open suse 12.1

  - by Kapil Sharma

  I know linux basics but not an expert. IT guy left the job here and there is some time before new hire. So sorry if question is very basic. We have local testing server based on Open SUSE 12.1, which also act as shared drive between dev/mgmt team here and using Samba for that. Now we are running out of space on samba, even though server's 2*1TB harddisk is nearly 90% free. My question is, what is limiting Samba and how can I increase its limit? We need around at least 500 GB as shared drive but currently its just 25 GB. I don't need step by step answer, just a link to any helpful article would be sufficient. Probably I'm putting wrong keywords in google so not getting any helpful link. EDIT: Output of commands in the first comment. All commands were run as root user df -h (getting error with df -ht) Filesystem Size Used Avail Use% Mounted on rootfs 30G 5.1G 23G 19% / devtmpfs 2.0G 36K 2.0G 1% /dev tmpfs 2.0G 1.1M 2.0G 1% /dev/shm tmpfs 2.0G 676K 2.0G 1% /run /dev/sda2 30G 5.1G 23G 19% / tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup tmpfs 2.0G 676K 2.0G 1% /var/run tmpfs 2.0G 0 2.0G 0% /media tmpfs 2.0G 676K 2.0G 1% /var/lock /dev/sda3 36G 31G 3.3G 91% /home fdisk -l /dev/[hmsv]d* Disk /dev/sda: 80.0 GB, 80026361856 bytes 255 heads, 63 sectors/track, 9729 cylinders, total 156301488 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x2d4a2d49 Device Boot Start End Blocks Id System /dev/sda1 2048 16771071 8384512 82 Linux swap / Solaris /dev/sda2 * 16771072 79681535 31455232 83 Linux /dev/sda3 79681536 156301311 38309888 83 Linux Disk /dev/sda1: 8585 MB, 8585740288 bytes 255 heads, 63 sectors/track, 1043 cylinders, total 16769024 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sda1 doesn't contain a valid partition table Disk /dev/sda2: 32.2 GB, 32210157568 bytes 255 heads, 63 sectors/track, 3915 cylinders, total 62910464 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System Disk /dev/sda3: 39.2 GB, 39229325312 bytes 255 heads, 63 sectors/track, 4769 cylinders, total 76619776 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sda3 doesn't contain a valid partition table vgs No volume groups found lvs No volume groups found output of vi /etc/samba/smb.conf # smb.conf is the main Samba configuration file. You find a full commented # version at /usr/share/doc/packages/samba/examples/smb.conf.SUSE if the # samba-doc package is installed. # Date: 2011-11-02 [global] workgroup = WORKGROUP passdb backend = tdbsam printing = cups printcap name = cups printcap cache time = 750 cups options = raw map to guest = Bad User include = /etc/samba/dhcp.conf logon path = \\%L\profiles\.msprofile logon home = \\%L\%U\.9xprofile logon drive = P: usershare allow guests = Yes [homes] comment = Home Directories valid users = %S, %D%w%S browseable = No read only = No inherit acls = Yes [profiles] comment = Network Profiles Service path = %H read only = No store dos attributes = Yes create mask = 0600 directory mask = 0700 [users] comment = All users path = /home read only = No inherit acls = Yes veto files = /aquota.user/groups/shares/ [groups] comment = All groups path = /home/groups read only = No inherit acls = Yes [printers] comment = All Printers path = /var/tmp printable = Yes create mask = 0600 browseable = No [print$] comment = Printer Drivers path = /var/lib/samba/drivers write list = @ntadmin root force group = ntadmin create mask = 0664 directory mask = 0775 [allusers] comment = All Users path = /home/shares/allusers valid users = @users force group = users create mask = 0660 directory mask = 0771 writable = yes

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• What are the pitfalls of hardlinked files on my desktop PC?

  - by MountainX

  All the identical-content files on my PC are now hardlinked. (My data is completely de-duplicated. It is a consequence of the way I copied my data from my old computer.) What pitfalls do I need to be aware of now that certain actions on one file could silently affect a number of other files? I know that deleting the file I'm working on is not a problem (assuming I deleted it on purpose). It doesn't affect any of the other hardlinked files and I don't see that the delete action would lead to unexpected side effects. Moving or renaming the file is not a problem. I don't see any unexpected consequences. I don't think copying hardlinked files is a problem, but I'm not as confident about any unexpected consequences in this regard. What I have seen is that making a copy (to the same disk) of a hardlinked file with cp keeps the copy hardlinked (i.e., inode number doesn't change in the copy). Copying to another filesystem obviously breaks the hardlink. (I guess one pitfall is forgetting this fact, given that my PC has 3 hard disks.) Changing permissions does affect all linked files. So far this has proven handy. (I made a large number of the hardlinked files read-only.) None of the operations above seem to produce any major unexpected consequences. However, as was pointed out to me by Daniel Beck in a comment, editing or modifying a file can sometimes be a problem. It depends on the tool and maybe the type of edit. (For example, editing small text files using sed seems to always break the link while using nano doesn't.) This introduces the chance that editing one file could affect all the hardlinked files (i.e., alter the original inode). My proposed solution to this is to make all hardlinked files read-only (and that is already mostly the case). If I can't do that for some files, I will unlink those particular files. Is there any problem with this read-only approach? I'm assuming that if I go to edit a file and find it to be read-only, I'll remember to unlink that filename while making it writable. So one pitfall might be forgetting this rule. In that case, I'll have to rely on my backups. Am I correct in the above statements? And what else do I need to know? BTW, I'm running Kubuntu 12.04. I'm also using btrfs. (I have 2 SSD's and 1 HDD in the PC. I will also be adding an external USB HDD. I'm also connected to a network and I mount some NFS shares. I don't assume any of these last bits are relevant to the question, but I'm adding them just in case.) BTW, since I have more than one drive (with separate file systems), to unlink any file all I have to do is copy it to another drive, then move it back. However, using sed also works (in my testing). Here's my script: sed -i 's/\(.\)/\1/' file1 Surprisingly, this even unlinks zero byte files. In my testing it also appears to work on non-text files without any special options. (But I understand that the --binary option might be needed on Windows, MS-DOS and Cygwin.) However, copying to another disk and moving back may be the best way to unlink. For my use-case, unlink command doesn't really "unlink", rather it "removes".

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• collectd does not work

  - by bery

  I have installed collectd-5.0.0 on Fedora12 server and would like to run its service for receiving data from clients. I have enabled network plugin and rddtool plugin as commented: collectd.conf in server: BaseDir "/opt/collectd/var/lib/collectd" LoadPlugin "logfile" LoadPlugin network LoadPlugin rrdtool <Plugin network> Listen "192.168.8.37" "25826" </Plugin> collectd.conf in client: LoadPlugin logfile LoadPlugin cpu LoadPlugin network LoadPlugin memory <Plugin network> Server"192.168.8.37" "25826" </Plugin> collectd.log in server: [2011-08-03 02:36:04] Exiting normally. [2011-08-03 02:36:04] rrdtool plugin: Shutting down the queue thread. [2011-08-03 02:36:04] network plugin: Stopping receive thread. [2011-08-03 02:36:04] network plugin: Stopping dispatch thread. [2011-08-03 02:37:11] Initialization complete, entering read-loop. collectd.log in client: [2011-08-02 17:31:44] Initialization complete, entering read-loop. results thst execute netstat on server: netstat -ulpn | grep 25826 udp 0 0 192.168.8.37:25826 0.0.0.0:* 4744/collectd problem: but there is noting in "/opt/collectd/var/lib/collectd/" on ser yes,I move the port number of "25826" as your propose(But I think this is the default port for coolectd).there is no rdd files recived on server. collectd.log in client collectd [2011-08-03 10:01:36] plugin_read_thread: Handling memory'. [2011-08-03 10:01:36] plugin_read_thread: Handlingcpu'. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = used; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = user; [2011-08-03 10:01:36] uc_update: uml/memory/memory-used: ds[0] = 280412160.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-user: ds[0] = 0.100008 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = buffered; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = nice; [2011-08-03 10:01:36] uc_update: uml/memory/memory-buffered: ds[0] = 344182784.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-nice: ds[0] = 0.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] network plugin: flush_buffer: send_buffer_fill = 1340 [2011-08-03 10:01:36] network plugin: network_send_buffer: buffer_len = 1340 ... [2011-08-03 10:01:36] plugin_read_thread: Next read of the cpu plugin at 1312380106.429064774. collectd.log in server collectd: [2011-08-03 20:18:08] type = network [2011-08-03 20:18:08] type = rrdtool [2011-08-03 20:18:08] network plugin: sockent_open: node = 192.168.8.37; service = 25826; [2011-08-03 20:18:08] fd = 3; calling bind' [2011-08-03 20:18:08] Done parsing/opt/collectd//share/collectd/types.db' [2011-08-03 20:18:08] interval_g = 10; [2011-08-03 20:18:08] timeout_g = 2; [2011-08-03 20:18:08] hostname_g = localhost.localdomain; [2011-08-03 20:18:08] Initialization complete, entering read-loop. It looks like, data is sending but doesn't be recived. Where is the mistake?

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• rpm rollback ignoring rpms - no error output

  - by John H

  Issue rpm rollback is not working with a set of repackaged rpms created in the last couple days, but does work with more recent ones. [root@host1 repackage]# ls -l zsh-4.2.6-* -rw-r--r-- 1 root root 1788283 Apr 10 2011 zsh-4.2.6-3.el5.i386.rpm -rw-r--r-- 1 root root 1788691 Aug 18 04:38 zsh-4.2.6-5.el5.i386.rpm [root@host1 repackage]# rpm -q zsh zsh-4.2.6-6.el5 [root@host1 repackage]# rpm --test -Uvh --rollback 'Aug 18 01:00' [root@host1 repackage]# rpm -e zsh [root@host1 repackage]# [root@host1 repackage]# ls -l zsh* -rw-r--r-- 1 root root 1788283 Apr 10 2011 zsh-4.2.6-3.el5.i386.rpm -rw-r--r-- 1 root root 1788691 Aug 18 04:38 zsh-4.2.6-5.el5.i386.rpm -rw-r--r-- 1 root root 1789064 Aug 20 09:06 zsh-4.2.6-6.el5.i386.rpm [root@host1 repackage]# cp zsh-4.2.6-6.el5.i386.rpm /tmp [root@host1 repackage]# rpm --test -Uvh --rollback 'Aug 18 01:00' Rollback packages (+1/-0) to Mon Aug 20 09:02:16 2012 (0x50323558): Preparing... ########################################### [100%] Cleaning up repackaged packages: Removing /var/spool/repackage/zsh-4.2.6-6.el5.i386.rpm: [root@host1 repackage]# ls -l zsh-4.2.6-* -rw-r--r-- 1 root root 1788283 Apr 10 2011 zsh-4.2.6-3.el5.i386.rpm -rw-r--r-- 1 root root 1788691 Aug 18 04:38 zsh-4.2.6-5.el5.i386.rpm [root@host1 repackage]# cp /tmp/zsh-4.2.6-6.el5.i386.rpm . [root@host1 repackage]# rpm -Uvh --rollback 'Aug 18 01:00' Rollback packages (+1/-0) to Mon Aug 20 09:06:05 2012 (0x5032363d): Preparing... ########################################### [100%] 1:zsh ########################################### [ 50%] Cleaning up repackaged packages: Removing /var/spool/repackage/zsh-4.2.6-6.el5.i386.rpm: [root@host1 repackage]# rpm --test -Uvh --rollback 'April 9' [root@host1 repackage]# Now, if I run my test commands with -Uvvh I get debug messages to stderror which shows me that rpm reads each of the rpm files in /var/spool/repackage. The only interesting bit is the "expected size" but after searching, the expected size should be different, as it records the files as they are on the filesystem. D: opening db environment /var/lib/rpm/Packages joinenv D: opening db index /var/lib/rpm/Packages rdonly mode=0x0 D: locked db index /var/lib/rpm/Packages D: opening db index /var/lib/rpm/Installtid rdonly mode=0x0 D: opening db index /var/lib/rpm/Pubkeys rdonly mode=0x0 D: read h# 769 Header sanity check: OK D: ========== DSA pubkey id 53268101 37017186 (h#769) D: read h# 32 Header V3 DSA signature: OK, key ID 37017186 D: read h# 40 Header V3 DSA signature: OK, key ID 37017186 ... D: read h# 1753 Header V3 DSA signature: OK, key ID 37017186 D: Expected size: 3628918 = lead(96)+sigs(344)+pad(0)+data(3628478) D: Actual size: 3583695 D: /var/spool/repackage/Deployment_Guide-en-US-5.2-11.noarch.rpm: Header V3 DSA signature: OK, key ID 37017186 D: Expected size: 1100789 = lead(96)+sigs(344)+pad(0)+data(1100349) D: Actual size: 1109281 D: /var/spool/repackage/NetworkManager-0.7.0-10.el5_5.2.i386.rpm: Header V3 DSA signature: OK, key ID 37017186 D: Expected size: 1098167 = lead(96)+sigs(344)+pad(0)+data(1097727) D: Actual size: 1106179 D: /var/spool/repackage/NetworkManager-0.7.0-9.el5.i386.rpm: Header V3 DSA signature: OK, key ID 37017186 D: Expected size: 84351 = lead(96)+sigs(344)+pad(0)+data(83911) D: Actual size: 85378 ... D: Expected size: 1788276 = lead(96)+sigs(344)+pad(0)+data(1787836) D: Actual size: 1788691 D: /var/spool/repackage/zsh-4.2.6-5.el5.i386.rpm: Header V3 DSA signature: OK, key ID 37017186 D: --- erase h#1758 D: closed db index /var/lib/rpm/Pubkeys D: closed db index /var/lib/rpm/Installtid D: closed db index /var/lib/rpm/Packages D: closed db environment /var/lib/rpm/Packages D: May free Score board((nil)) I am able to copy these rpms out of the repackage directory and if I run them through cpio, extract the files. I also tried backing up and rebuilding the rpm database - no change. System Information: RHEL 5.8 rpm 4.4.2.3 /etc/yum.conf tsflags=repackage /etc/rpm/macros %_repackage_all_erasures 1

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• Samba4 [homes] share

  - by SambaDrivesMeCrazy

  I am having issues with the [homes] share. OS is Ubuntu 12.04. I've installed samba 4.0.3, bind9 dlz, ntp, winbind, everything but pam modules, and did all the tests from https://wiki.samba.org/index.php/Samba_AD_DC_HOWTO. Running getent passwd and getent user work just fine. Creating a simple share works just fine too. I can manage the users, GPOs, and DNS from the windows mmc snap-ins. I can join winxp,7,8 to the domain and log on perfectly. I can change my passwords from windows, etc..etc.. I could say that everything is fine and be happy :) buuuut, no, home directories do not work. Searching in here, and on our good friend google I gathered that a simple [homes] read only = no path = /storage-server/users/ and mapping the user's home folder in dsa.msc to \\server-001\username or \\server-001\homes should get me a home share I could map for my user homedir. But the snap-in give me an error saying that it cannot create the home folder because the network name has not been found (rough translation from portuguese). also, running root@server-001:/storage-server/users# smbclient //server-001/test -Utest%'12345678' -c 'ls' Domain=[MYDOMAIN] OS=[Unix] Server=[Samba 4.0.3] tree connect failed: NT_STATUS_BAD_NETWORK_NAME Server name is alright, if I go for a simple share on the same server it opens just fine. If I map the user homedir to this simple share it works. What I want is that I dont have to go and manually make a new folder on linux everytime I create a new user on windows. It looks like permissions but I cant find any documentation on this (yes I've tried the manpages, but its hard to tell with so many options on man smb.conf alone). My smb.conf right now looks like this (pretty simple I know) # Global parameters [global] workgroup = MYDOMAIN realm = MYDOMAIN.LAN netbios name = SERVER-001 server role = active directory domain controller server services = s3fs, rpc, nbt, wrepl, ldap, cldap, kdc, drepl, winbind, ntp_signd, kcc, dnsupdate [netlogon] path = /usr/local/samba/var/locks/sysvol/mydomain.lan/scripts read only = No [sysvol] path = /usr/local/samba/var/locks/sysvol read only = No [homes] read only = no path = /storage-server/users Folder permissions /storage-server drwxr-xr-x 6 root root 4096 Fev 15 15:17 storage-server /storage-server/users drwxrwxrwx 6 root root 4096 Fev 18 17:05 users/ Yes, I was desperate enough to set 777 on the users folder... not proud of it. Any pointers in the right direction would be very welcome. Edited to include: root@server-001:/# wbinfo --user-info=test MYDOMAIN\test:*:3000045:100:test:/home/MYDOMAIN/test:/bin/false root@server-001:/# wbinfo -n test S-1-5-21-1957592451-3401938807-633234758-1128 SID_USER (1) root@server-001:/# id test uid=3000045(MYDOMAIN\test) gid=100(users) grupos=100(users) root@server-001:/# wbinfo -U 3000045 S-1-5-21-1957592451-3401938807-633234758-1128 root@server-001:/# Edit 2: getent passwd | grep test MYDOMAIN\test:*:3000045:100:test:/home/MYDOMAIN/test:/bin/false I have no idea how to change that home folder to /storage-server/users/test so I just went and ln -s /storage-server/users /home/MYDOMAIN just in case. still, no changes, same errors. Edit 3 On log.smbd I get the following error when trying to set the test user home folder to \server-001\test [2013/02/20 14:22:08.446658, 2] ../source3/smbd/service.c:418(create_connection_session_info) user 'MYDOMAIN\Administrator' (from session setup) not permitted to access this share (test)

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• reiserfsck on lvm

  - by DaDaDom

  It seems like my filesystem got corrupted somehow during the last reboot of my server. I can't fsck some logical volumes anymore. The setup: root@rescue ~ # cat /mnt/rescue/etc/fstab proc /proc proc defaults 0 0 /dev/md0 /boot ext3 defaults 0 2 /dev/md1 / ext3 defaults,errors=remount-ro 0 1 /dev/systemlvm/home /home reiserfs defaults 0 0 /dev/systemlvm/usr /usr reiserfs defaults 0 0 /dev/systemlvm/var /var reiserfs defaults 0 0 /dev/systemlvm/tmp /tmp reiserfs noexec,nosuid 0 2 /dev/sda5 none swap defaults,pri=1 0 0 /dev/sdb5 none swap defaults,pri=1 0 0 [UPDATE] First question: what "part" should I check for bad blocks? The logical volume, the underlying /dev/md or the /dev/sdx below that? Is doing what I am doing the right way to go? [/UPDATE] The errormessage when checking /dev/systemlvm/usr: root@rescue ~ # reiserfsck /dev/systemlvm/usr reiserfsck 3.6.19 (2003 www.namesys.com) [...] Will read-only check consistency of the filesystem on /dev/systemlvm/usr Will put log info to 'stdout' Do you want to run this program?[N/Yes] (note need to type Yes if you do):Yes ########### reiserfsck --check started at Wed Feb 3 07:10:55 2010 ########### Replaying journal.. Reiserfs journal '/dev/systemlvm/usr' in blocks [18..8211]: 0 transactions replayed Checking internal tree.. Bad root block 0. (--rebuild-tree did not complete) Aborted Well so far, let's try --rebuild-tree: root@rescue ~ # reiserfsck --rebuild-tree /dev/systemlvm/usr reiserfsck 3.6.19 (2003 www.namesys.com) [...] Will rebuild the filesystem (/dev/systemlvm/usr) tree Will put log info to 'stdout' Do you want to run this program?[N/Yes] (note need to type Yes if you do):Yes Replaying journal.. Reiserfs journal '/dev/systemlvm/usr' in blocks [18..8211]: 0 transactions replayed ########### reiserfsck --rebuild-tree started at Wed Feb 3 07:12:27 2010 ########### Pass 0: ####### Pass 0 ####### Loading on-disk bitmap .. ok, 269716 blocks marked used Skipping 8250 blocks (super block, journal, bitmaps) 261466 blocks will be read 0%....20%....40%....60%....80%....100% left 0, 11368 /sec 52919 directory entries were hashed with "r5" hash. "r5" hash is selected Flushing..finished Read blocks (but not data blocks) 261466 Leaves among those 13086 Objectids found 53697 Pass 1 (will try to insert 13086 leaves): ####### Pass 1 ####### Looking for allocable blocks .. finished 0% left 12675, 0 /sec The problem has occurred looks like a hardware problem (perhaps memory). Send us the bug report only if the second run dies at the same place with the same block number. mark_block_used: (39508) used already Aborted Bad. But let's do it again as mentioned: [...] Flushing..finished Read blocks (but not data blocks) 261466 Leaves among those 13085 Objectids found 54305 Pass 1 (will try to insert 13085 leaves): ####### Pass 1 ####### Looking for allocable blocks .. finished 0%... left 12127, 958 /sec The problem has occurred looks like a hardware problem (perhaps memory). Send us the bug report only if the second run dies at the same place with the same block number. build_the_tree: Nothing but leaves are expected. Block 196736 - internal Aborted Same happens every time, only the actual error message changes. Sometimes I get mark_block_used: (somenumber) used already, other times the block number changes. Seems like something is REALLY broken. Are there any chances I can somehow get the partitions to work again? It's a server to which I don't have physical access directly (hosted server). Thanks in advance!

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• How to setup linux permissions the WWW folder?

  - by Xeoncross

  Updated Summery The /var/www directory is owned by root:root which means that no one can use it and it's entirely useless. Since we all want a web server that actually works (and no-one should be logging in as "root"), then we need to fix this. Only two entities need access. PHP/Perl/Ruby/Python all need access to the folders and files since they create many of them (i.e. /uploads/). These scripting languages should be running under nginx or apache (or even some other thing like FastCGI for PHP). The developers How do they get access? I know that someone, somewhere has done this before. With however-many billions of websites out there you would think that there would be more information on this topic. I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions. What permissions are need to be used on /var/www so that... Source control like git or svn Users in a group like "websites" (or even added to "www-data") Servers like apache or lighthttpd And PHP/Perl/Ruby can all read, create, and run files (and directories) there? If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www...? Therefore, it seems like the correct permission would be chmod -R 1660 which would make all files shareable by these four entities all files non-executable by mistake block everyone else from the directory entirely set the permission mode to "sticky" for all future files Is this correct? Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be. Update 2: The folder structure of /var/www changes drastically as one of the four entities above are always adding (and sometimes removing) folders and sub folders many levels deep. They also create and remove files that the other 3 entities might need read/write access to. Therefore, the permissions need to do the four things above for both files and directories. Since non of them should need execute permission (see question about ruby/php above) I would assume that rw-rw-r-- permission would be all that is needed and completely safe since these four entities are run by trusted personal (see #2) and all other users on the system only have read access. Update 3: This is for personal development machines and private company servers. No random "web customers" like a shared host. Update 4: This article by slicehost seems to be the best at explaining what is needed to setup permissions for your www folder. However, I'm not sure what user or group apache/nginx with PHP OR svn/git run as and how to change them. Update 5: I have (I think) finally found a way to get this all to work (answer below). However, I don't know if this is the correct and SECURE way to do this. Therefore I have started a bounty. The person that has the best method of securing and managing the www directory wins.

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• Wear and tear on server hard drive from filesystem polling by PHP script

  - by jackie

  So I'm working on a discussion platform, and various clients will visit http://host/thread.php, which will render the discussion thread to date in addition to a form to submit a new post. When a new post is submitted, I would like all of the other clients with browser windows open to have it appear in near-real-time. One of the constraints of my script is that it may not use a DBMS and it must stay in the filesystem. Additionally, I can't use any PECL/PEAR extensions like inotify or anything like that for IPC. The flow will look like this: Client A requests thread.php and the thread is so far empty, but nonetheless it opens a Server-Side Event at eventPusher.php. Client B does the same. Client A fills out a post in the form and and submits (POSTs) it to subHandler.php. ??? (subHandler stores the new submission into the main thread storefile which gets read from when a fresh, new client requests thread.php, in addition to somehow signalling to the continually-running eventPusher event-source that a new comment was posted and that it should echo the event-json to the client. How, exactly, it will send this signal I'm yet unsure of, but there are a few options that I've thought of -- this is the crux of the question, so see below for more clarification) eventPusher.php happily pushes the new event to the client and it shows up soon after it was originally submitted on all clients who have the page open's screens. Now for the #4 missing-link mystery-step, I see a few problems. I mean, either way, eventPusher is gonna be doing a while loop of some sort -- it's gonna be polling something, I think that much is clear. (If that's a bad assumption please do let me know.) Now, the simplest way would be subHandler gets invoked on the form submission, writes it to the main store in addition to newComments.xml, then exits without doing anything else. Then eventPusher checks in newComments.xml every X seconds (by the way, what would be a reasonable time interval here?) and if it finds something then it emits an event to the client. Now, my fear with this is that the server's hard drive will have to constantly start spinning up. Maybe this isn't the case, perhaps it would just get cached in RAM and the linux kernel would take care of this transparently such that filesystem access doesn't actually engage the device because the kernel knows that that particular file hasn't changed since last read. * idea #2: I have no idea how to go about this, but perhaps there is a variable scope that gets stored in general RAM on the system which can be read by any process. Like if we mega-exported a bash variable so that $new_post is normally false but it gets toggled to true by subHandler, and then back to flase once it's pushed to the client. I doubt there's such a variable scope in PHP directly, but I struggle with the concept of variable scope, I just can't seem to understand it no matter what I read on it. * idea #3: eventPusher queries ps in its whileloop for another instance of itself. If there's not another eventPusher active then it's highly unlikely that new comments will be getting submitted. It's okay if this only works =90% of the time, it doesn't need to be completely foolproof. * idea #4: eventPusher queries DMESG to see if that file's been written to recently. So to sum everything up, I need to have inter-php-script-communication in near-real-time that will work on a standard mod_php shared hosting setup without any elevated privileges, PHP addon modules, or other system adjustments that can't be done from the PHP script itself at runtime. With*out* spinning up the drive more than a few times. No SQL servers either. Apologies if my english isn't the best, I'm still trying to improve on it.

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• stunnel crashing

  - by Jay

  I'm trying to use stunnel to secure a legacy application's communications. I can't seem to get it setup and working. Can anyone provide any hints where I'm going wrong? Here's what I'm trying to accomplish: A windows service on a client machine connects to a server on port 7000 using TCP. I'd like to encrypt the communication between client and server. Here's what I've tried: Created a new server that accepts ssl connections on port 7443. Got a certificate for the server and installed it. That seems to work with my test setup. Installed stunnel on my windows machine (version 7.43 from the distribution archive file). Installed libssl32.dll and libeay32.dll in the same directory as stunnel.exe ( from the openssl-0.9.8h-1 binary distribution). Installed it as a service using "stunnel -install" Configured stunnel as follows: debug=7 output=C:\p4\internal\Utility\Proxy\proxy.log service=Proxy taskbar=no [exchange] accept=7000 client=yes connect=proxy.blah.com:7443 I changed my hosts file to trick the old application into connecting through stunnel: server.blah.com 127.0.0.1 # when client looks up server it goes to stunnel proxy.blah.com IP-address-of-server.blah.com # stunnel connects to new server "server.blah.com" now resolves to the machine it's running on (i.e. stunnel). "proxy.blah.com" goes to the real server. stunnel should connect to the server. I start the stunnel service and try to connect. It looks like it's working but the stunnel service just shuts down with no message. 2010.04.19 13:16:21 LOG5[4924:3716]: stunnel 4.33 on x86-pc-mingw32-gnu with OpenSSL 0.9.8h 28 May 2008 2010.04.19 13:16:21 LOG5[4924:3716]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 2010.04.19 13:16:49 LOG5[4924:3748]: Service exchange accepted connection from 127.0.0.1:4134 2010.04.19 13:16:49 LOG6[4924:3748]: connect_blocking: connecting x.80.60.32:7443 2010.04.19 13:16:49 LOG5[4924:3748]: connect_blocking: connected x.80.60.32:7443 2010.04.19 13:16:49 LOG5[4924:3748]: Service exchange connected remote server from x.253.120.19:4135 2010.04.19 13:20:24 LOG5[3668:3856]: Reading configuration from file stunnel.conf 2010.04.19 13:20:24 LOG7[3668:3856]: Snagged 64 random bytes from C:/.rnd 2010.04.19 13:20:24 LOG7[3668:3856]: Wrote 1024 new random bytes to C:/.rnd 2010.04.19 13:20:24 LOG7[3668:3856]: RAND_status claims sufficient entropy for the PRNG 2010.04.19 13:20:24 LOG7[3668:3856]: PRNG seeded successfully 2010.04.19 13:20:24 LOG7[3668:3856]: SSL context initialized for service exchange 2010.04.19 13:20:24 LOG5[3668:3856]: Configuration successful 2010.04.19 13:20:24 LOG5[3668:3856]: No limit detected for the number of clients 2010.04.19 13:20:24 LOG7[3668:3856]: FD=312 in non-blocking mode 2010.04.19 13:20:24 LOG7[3668:3856]: Option SO_REUSEADDR set on accept socket 2010.04.19 13:20:24 LOG7[3668:3856]: Service exchange bound to 0.0.0.0:7000 2010.04.19 13:20:24 LOG7[3668:3856]: Service exchange opened FD=312 2010.04.19 13:20:24 LOG5[3668:3856]: stunnel 4.33 on x86-pc-mingw32-gnu with OpenSSL 0.9.8h 28 May 2008 2010.04.19 13:20:24 LOG5[3668:3856]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 2010.04.19 13:21:02 LOG7[3668:4556]: Service exchange accepted FD=372 from 127.0.0.1:4156 2010.04.19 13:21:02 LOG7[3668:4556]: Creating a new thread 2010.04.19 13:21:02 LOG7[3668:4556]: New thread created 2010.04.19 13:21:02 LOG7[3668:3756]: Service exchange started 2010.04.19 13:21:02 LOG7[3668:3756]: FD=372 in non-blocking mode 2010.04.19 13:21:02 LOG5[3668:3756]: Service exchange accepted connection from 127.0.0.1:4156 2010.04.19 13:21:02 LOG7[3668:3756]: FD=396 in non-blocking mode 2010.04.19 13:21:02 LOG6[3668:3756]: connect_blocking: connecting x.80.60.32:7443 2010.04.19 13:21:02 LOG7[3668:3756]: connect_blocking: s_poll_wait x.80.60.32:7443: waiting 10 seconds 2010.04.19 13:21:02 LOG5[3668:3756]: connect_blocking: connected x.80.60.32:7443 2010.04.19 13:21:02 LOG5[3668:3756]: Service exchange connected remote server from x.253.120.19:4157 2010.04.19 13:21:02 LOG7[3668:3756]: Remote FD=396 initialized 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): before/connect initialization 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write client hello A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server hello A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server certificate A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read server done A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write client key exchange A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write change cipher spec A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 write finished A 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 flush data 2010.04.19 13:21:02 LOG7[3668:3756]: SSL state (connect): SSLv3 read finished A The client thinks the connection is closed: No connection could be made because the target machine actively refused it 127.0.0.1:7000 at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.Sockets.Socket.Connect(EndPoint remoteEP) at Service.ConnUtility.Connect() Any suggestions?

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• openvpn WARNING: No server certificate verification method has been enabled

  - by tmedtcom

  I tried to install openvpn on debian squeez (server) and connect from my fedora 17 as (client). Here is my configuration: server configuration ###cat server.conf # Serveur TCP ** proto tcp** port 1194 dev tun # Cles et certificats ca /etc/openvpn/easy-rsa/keys/ca.crt cert /etc/openvpn/easy-rsa/keys/server.crt key /etc/openvpn/easy-rsa/keys/server.key dh /etc/openvpn/easy-rsa/keys/dh1024.pem # Reseau #Adresse virtuel du reseau vpn server 192.170.70.0 255.255.255.0 #Cette ligne ajoute sur le client la route du reseau vers le serveur push "route 192.168.1.0 255.255.255.0" #Creer une route du server vers l'interface tun. #route 192.170.70.0 255.255.255.0 # Securite keepalive 10 120 #type d'encryptage des données **cipher AES-128-CBC** #activation de la compression comp-lzo #nombre maximum de clients autorisés max-clients 10 #pas d'utilisateur et groupe particuliers pour l'utilisation du VPN user nobody group nogroup #pour rendre la connexion persistante persist-key persist-tun #Log d'etat d'OpenVPN status /var/log/openvpn-status.log #logs openvpnlog /var/log/openvpn.log log-append /var/log/openvpn.log #niveau de verbosité verb 5 ###cat client.conf # Client client dev tun [COLOR="Red"]proto tcp-client[/COLOR] remote <my server wan IP> 1194 resolv-retry infinite **cipher AES-128-CBC** # Cles ca ca.crt cert client.crt key client.key # Securite nobind persist-key persist-tun comp-lzo verb 3 Message from the host client (fedora 17) in the log file / var / log / messages: Dec 6 21:56:00 GlobalTIC NetworkManager[691]: <info> Starting VPN service 'openvpn'... Dec 6 21:56:00 GlobalTIC NetworkManager[691]: <info> VPN service 'openvpn' started (org.freedesktop.NetworkManager.openvpn), PID 7470 Dec 6 21:56:00 GlobalTIC NetworkManager[691]: <info> VPN service 'openvpn' appeared; activating connections Dec 6 21:56:00 GlobalTIC NetworkManager[691]: <info> VPN plugin state changed: starting (3) Dec 6 21:56:01 GlobalTIC NetworkManager[691]: <info> VPN connection 'Connexion VPN 1' (Connect) reply received. Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]: OpenVPN 2.2.2 x86_64-redhat-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] built on Sep 5 2012 Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]:[COLOR="Red"][U][B] WARNING: No server certificate verification method has been enabled.[/B][/U][/COLOR] See http://openvpn.net/howto.html#mitm for more info. Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]:[COLOR="Red"] WARNING: file '/home/login/client/client.key' is group or others accessible[/COLOR] Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]: UDPv4 link local: [undef] Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]: UDPv4 link remote: [COLOR="Red"]<my server wan IP>[/COLOR]:1194 Dec 6 21:56:01 GlobalTIC nm-openvpn[7472]: [COLOR="Red"]read UDPv4 [ECONNREFUSED]: Connection refused (code=111)[/COLOR] Dec 6 21:56:03 GlobalTIC nm-openvpn[7472]: [COLOR="Red"]read UDPv4[/COLOR] [ECONNREFUSED]: Connection refused (code=111) Dec 6 21:56:07 GlobalTIC nm-openvpn[7472]: read UDPv4 [ECONNREFUSED]: Connection refused (code=111) Dec 6 21:56:15 GlobalTIC nm-openvpn[7472]: read UDPv4 [ECONNREFUSED]: Connection refused (code=111) Dec 6 21:56:31 GlobalTIC nm-openvpn[7472]: read UDPv4 [ECONNREFUSED]: Connection refused (code=111) Dec 6 21:56:41 GlobalTIC NetworkManager[691]: <warn> VPN connection 'Connexion VPN 1' (IP Conf[/CODE] ifconfig on server host(debian): ifconfig eth0 Link encap:Ethernet HWaddr 08:00:27:16:21:ac inet addr:192.168.1.6 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fe16:21ac/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:9059 errors:0 dropped:0 overruns:0 frame:0 TX packets:5660 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:919427 (897.8 KiB) TX bytes:1273891 (1.2 MiB) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.170.70.1 P-t-P:192.170.70.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) ifconfig on the client host (fedora 17) as0t0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 5.5.0.1 netmask 255.255.252.0 destination 5.5.0.1 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 200 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 2 bytes 321 (321.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 as0t1: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 5.5.4.1 netmask 255.255.252.0 destination 5.5.4.1 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 200 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 2 bytes 321 (321.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 as0t2: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 5.5.8.1 netmask 255.255.252.0 destination 5.5.8.1 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 200 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 2 bytes 321 (321.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 as0t3: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 5.5.12.1 netmask 255.255.252.0 destination 5.5.12.1 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 200 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 2 bytes 321 (321.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 **p255p1**: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fe80::21d:baff:fe20:b7e6 prefixlen 64 scopeid 0x20<link> ether 00:1d:ba:20:b7:e6 txqueuelen 1000 (Ethernet) RX packets 4842070 bytes 3579798184 (3.3 GiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 3996158 bytes 2436442882 (2.2 GiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 16 p255p1 is label for eth0 interface and on the server : root@hoteserver:/etc/openvpn# tree . +-- client ¦** +-- ca.crt ¦** +-- client.conf ¦** +-- client.crt ¦** +-- client.csr ¦** +-- client.key ¦** +-- client.ovpn ¦* ¦** +-- easy-rsa ¦** +-- build-ca ¦** +-- build-dh ¦** +-- build-inter ¦** +-- build-key ¦** +-- build-key-pass ¦** +-- build-key-pkcs12 ¦** +-- build-key-server ¦** +-- build-req ¦** +-- build-req-pass ¦** +-- clean-all ¦** +-- inherit-inter ¦** +-- keys ¦** ¦** +-- 01.pem ¦** ¦** +-- 02.pem ¦** ¦** +-- ca.crt ¦** ¦** +-- ca.key ¦** ¦** +-- client.crt ¦** ¦** +-- client.csr ¦** ¦** +-- client.key ¦** ¦** +-- dh1024.pem ¦** ¦** +-- index.txt ¦** ¦** +-- index.txt.attr ¦** ¦** +-- index.txt.attr.old ¦** ¦** +-- index.txt.old ¦** ¦** +-- serial ¦** ¦** +-- serial.old ¦** ¦** +-- server.crt ¦** ¦** +-- server.csr ¦** ¦** +-- server.key ¦** +-- list-crl ¦** +-- Makefile ¦** +-- openssl-0.9.6.cnf.gz ¦** +-- openssl.cnf ¦** +-- pkitool ¦** +-- README.gz ¦** +-- revoke-full ¦** +-- sign-req ¦** +-- vars ¦** +-- whichopensslcnf +-- openvpn.log +-- openvpn-status.log +-- server.conf +-- update-resolv-conf on the client: [login@hoteclient openvpn]$ tree . |-- easy-rsa | |-- 1.0 | | |-- build-ca | | |-- build-dh | | |-- build-inter | | |-- build-key | | |-- build-key-pass | | |-- build-key-pkcs12 | | |-- build-key-server | | |-- build-req | | |-- build-req-pass | | |-- clean-all | | |-- list-crl | | |-- make-crl | | |-- openssl.cnf | | |-- README | | |-- revoke-crt | | |-- revoke-full | | |-- sign-req | | `-- vars | `-- 2.0 | |-- build-ca | |-- build-dh | |-- build-inter | |-- build-key | |-- build-key-pass | |-- build-key-pkcs12 | |-- build-key-server | |-- build-req | |-- build-req-pass | |-- clean-all | |-- inherit-inter | |-- keys [error opening dir] | |-- list-crl | |-- Makefile | |-- openssl-0.9.6.cnf | |-- openssl-0.9.8.cnf | |-- openssl-1.0.0.cnf | |-- pkitool | |-- README | |-- revoke-full | |-- sign-req | |-- vars | `-- whichopensslcnf |-- keys -> ./easy-rsa/2.0/keys/ `-- server.conf the problem source is cipher AES-128-CBC ,proto tcp-client or UDP or the interface p255p1 on fedora17 or file authentification ta.key is not found ????

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• The Complete List of iPad Tips, Tricks, and Tutorials

  - by Ross

  The Apple iPad is the latest new toy, and we’ve put together a comprehensive list of every tip, trick, and tutorial that we could find to help you get the most out of it—and we’re even giving one away to one lucky reader. So read on! Note: We’ll be keeping this page updated as we find more great articles, so you should bookmark this page for future reference. Want Your Own iPad? How-To Geek is Giving One Away! All you have to do to enter is become a fan of our Facebook page, and we’ll pick a random fan to win the prize. Win an iPad on the How-To Geek Facebook Fan Page Disable the “clicking sound” on the iPad Keyboard Does the clicking sound when you tap the iPad keyboard bother you? Thankfully it’s easy to disable with a couple of taps. How to disable the “clicking sound” on your iPad’s keyboard Enable and add bookmarks to the Safari Bookmarks Bar on your iPad By default, Safari doesn’t display the Bookmarks Bar. This tip shows you how to change that. How to enable and add bookmarks to the Safari Bookmarks Bar on your iPad Clear the Cache, History and Cookies in Safari for the iPad You’re probably used to clearing this kind of data right from within the browser. Not so with Safari on the iPad – but here’s how you can. How to clear the cache, history and cookies in Safari for iPad How to add more Apps to your iPad Dock The iPad has four icons in its ‘dock’. Did you know it can hold 6? How to add more Apps to your iPad Dock Convert PDF files to ePub files to read on your iPad with iBooks ePub is the format that iBooks are in. So for those of you with large eBook collections in PDF, here’s how you convert them to read in iBooks. How to convert PDF files to ePub files to read on your iPad with iBooks How to force your iPad to restart Has an app caused your iPad to freeze up, and you can’t escape? This tip shows you how to force your iPad to restart. How to force your iPad to restart How to export Keynote for iPad presentations to your Mac or PC Exporting Keynote presentations from your iPad to your Mac or PC isn’t as straight forward as you might have expected. This tutorial shows you how. How to export Keynote for iPad presentations to your Mac or PC How to import presentations to Keynote on your iPad Having trouble getting your presentations onto your iPad? How to import presentations to Keynote on your iPad How to import documents to Pages on your iPad This guide shows you how to transfer documents (MS Word or Pages) from your Mac/PC to your iPad. How to import documents to Pages on your iPad How to insert photos in a Pages document using iPad and share it as a PDF Want to spice up that doc with a picture you just took? This tutorial will show you how – and how to export that document as a PDF. How to insert photos in a Pages document using iPad and share it as a PDF How to lock your iPad If you have kids or co-workers/friends who think it’s funny to mess with your iPad – lock it. How to lock your iPad How to remove the “Sent from my iPad” signature from outgoing email on your iPad Does everyone need to know you just sent that email from your iPad? Probably not. This guide shows you how to remove the “Sent from my iPad” signature and replace it with your own (or none). How to remove the “Sent from my iPad” signature from outgoing email on your iPad How To Sync Multiple Calendars to the iPad With Google Sync This tutorial will show you a workaround on how to sync multiple calendars on your iPad using Google Sync. How to Sync Multiple Calendars to the iPad With Google Sync How to determine the MAC address of your iPad If your network restricts connections via MAC address – this guide will show you how to determine what yours is. How to determine the MAC address of your iPad How to take a screenshot of your iPad Do you need to take a screenshot of your iPad? This quick tip shows you how to do just that. How to take a screenshot of your iPad How to delete apps from your iPod Touch, iPhone or iPad Anyone who had an iPod Touch or iPhone before they had an iPad won’t need this tutorial. But if you’re new to the experience, this one will help. How to delete apps from your iPod Touch, iPhone or iPad How to determine the iPad ECID on Windows and Mac iPadintosh shows us how to determine the iPad’s ECID code – something you’ll want to have come Jailbreak time. How to grab the iPad ECID in Windows or OS X iPad Apps: Twitter and social networking essentials Enggadget has you covered with reviews of the first slew of iPad specific Twitter and other social networking apps. iPad Apps: Twitter and social networking essentials What does your website look like on an iPad? iPad Peek is a web based tool that allows you to enter any given URL, and it will display that page the same way Safari on the iPad does. Great for web site owners who don’t have access to an iPad. iPadPeek Stream Music and Videos to your iPad Gizmodo reviews the iPad app StreamToMe, which allows you to stream media from your Mac to your iPad across your local network. Their feelings in a nutshell – worth the $3, but not perfect. Review: StreamToMe for the iPad Apple iPad : Change links in Google Reader to point to full HTML webpage How to change links in Safari for iPad so that Google Reader points to a full HTML webpage How to connect an iPad to your existing wireless keyboard This video will show you how to connect your iPad to a wireless keyboard if you’re having any problems – and from the sound of things, quite a few folks are. via TUAW How to get started with the iPad Mashable has a very entry-level guide that will help you set up your iPad for the first time. Mashable’s Guide to Setting up the iPad Essential iPad Apps Downloadsquad gives mini-reviews to 8 iPad apps that you should install as soon as you get your iPad. iPad App Buyers Guide: Essential Apps you should get on day one Videos: The Official iPad Guided Tours From none other than Apple! Great getting started videos for all the included iPad apps. The Official iPad Guided Tours The Official iPad Manual When you buy an iPad, you don’t get a manual. But that’s not to say there isn’t one. Apple provides a 150 guide for your iPad in PDF format. The Official iPad Manual (pdf) How to print from your iPad Sure, it’s actually just an App (PrintCentral – $9.99 USD), but as of right now, it’s the only way. PrintCentral How to make your own iPad Wallpaper A perfectly detailed tutorial on how to make your own wallpaper for your iPad. The author also provides a really nice sample wallpaper, published under the Attribution-Noncommercial 2.0 Generic license. How to make your own iPad Wallpaper Got any more tips? Share them in the comments, and we’ll update the post with the links, or just the tip itself. Similar Articles Productive Geek Tips Want an iPad? How-To Geek is Giving One Away!Why Wait? Amazing New Add-on Turns Your iPhone into an iPad! [Comic]Clear the Auto-Complete Email Address Cache in OutlookAsk the Readers: Share Your Tips for Defeating Viruses and MalwareStupid Geek Tricks: Tile or Cascade Multiple Windows in Windows 7 TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Are You Blocked On Gtalk? Find out Discover Latest Android Apps On AppBrain The Ultimate Guide For YouTube Lovers Will it Blend? iPad Edition Penolo Lets You Share Sketches On Twitter Visit Woolyss.com for Old School Games, Music and Videos

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• Developer’s Life – Attitude and Communication – They Can Cause Problems – Notes from the Field #027

  - by Pinal Dave

  [Note from Pinal]: This is a 27th episode of Notes from the Field series. The biggest challenge for anyone is to understand human nature. We human have so many things on our mind at any moment of time. There are cases when what we say is not what we mean and there are cases where what we mean we do not say. We do say and things as per our mood and our agenda in mind. Sometimes there are incidents when our attitude creates confusion in the communication and we end up creating a situation which is absolutely not warranted. In this episode of the Notes from the Field series database expert Mike Walsh explains a very crucial issue we face in our career, which is not technical but more to relate to human nature. Read on this may be the best blog post you might read in recent times. In this week’s note from the field, I’m taking a slight departure from technical knowledge and concepts explained. We’ll be back to it next week, I’m sure. Pinal wanted us to explain some of the issues we bump into and how we see some of our customers arrive at problem situations and how we have helped get them back on the right track. Often it is a technical problem we are officially solving – but in a lot of cases as a consultant, we are really helping fix some communication difficulties. This is a technical blog post and not an “advice column” in a newspaper – but the longer I am a consultant, the more years I add to my experience in technology the more I learn that the vast majority of the problems we encounter have “soft skills” included in the chain of causes for the issue we are helping overcome. This is not going to be exhaustive but I hope that sharing four pieces of advice inspired by real issues starts a process of searching for places where we can be the cause of these challenges and look at fixing them in ourselves. Or perhaps we can begin looking at resolving them in teams that we manage. I’ll share three statements that I’ve either heard, read or said and talk about some of the communication or attitude challenges highlighted by the statement. 1 – “But that’s the SAN Administrator’s responsibility…” I heard that early on in my consulting career when talking with a customer who had serious corruption and no good recent backups – potentially no good backups at all. The statement doesn’t have to be this one exactly, but the attitude here is an attitude of “my job stops here, and I don’t care about the intent or principle of why I’m here.” It’s also a situation of having the attitude that as long as there is someone else to blame, I’m fine…  You see in this case, the DBA had a suspicion that the backups were not being handled right.  They were the DBA and they knew that they had responsibility to ensure SQL backups were good to go – it’s a basic requirement of a production DBA. In my “As A DBA Where Do I start?!” presentation, I argue that is job #1 of a DBA. But in this case, the thought was that there was someone else to blame. Rather than create extra work and take on responsibility it was decided to just let it be another team’s responsibility. This failed the company, the company’s customers and no one won. As technologists – we should strive to go the extra mile. If there is a lack of clarity around roles and responsibilities and we know it – we should push to get it resolved. Especially as the DBAs who should act as the advocates of the data contained in the databases we are responsible for. 2 – “We’ve always done it this way, it’s never caused a problem before!” Complacency. I have to say that many failures I’ve been paid good money to help recover from would have not happened had it been for an attitude of complacency. If any thoughts like this have entered your mind about your situation you may be suffering from it. If, while reading this, you get this sinking feeling in your stomach about that one thing you know should be fixed but haven’t done it.. Why don’t you stop and go fix it then come back.. “We should have better backups, but we’re on a SAN so we should be fine really.” “Technically speaking that could happen, but what are the chances?” “We’ll just clean that up as a fast follow” ..and so on. In the age of tightening IT budgets, increased expectations of up time, availability and performance there is no room for complacency. Our customers and business units expect – no demand – the best. Complacency says “we will give you second best or hopefully good enough and we accept the risk and know this may hurt us later. Sometimes an organization will opt for “good enough” and I agree with the concept that at times the perfect can be the enemy of the good. But when we make those decisions in a vacuum and are not reporting them up and discussing them as an organization that is different. That is us unilaterally choosing to do something less than the best and purposefully playing a game of chance. 3 – “This device must accept interference from other devices but not create any” I’ve paraphrased this one – but it’s something the Federal Communications Commission – a federal agency in the United States that regulates electronic communication – requires of all manufacturers of any device that could cause or receive interference electronically. I blogged in depth about this here (http://www.straightpathsql.com/archives/2011/07/relationship-advice-from-the-fcc/) so I won’t go into much detail other than to say this… If we all operated more on the premise that we should do our best to not be the cause of conflict, and to be less easily offended and less upset when we perceive offense life would be easier in many areas! This doesn’t always cause the issues we are called in to help out. Not directly. But where we see it is in unhealthy relationships between the various technology teams at a client. We’ll see teams hoarding knowledge, not sharing well with others and almost working against other teams instead of working with them. If you trace these problems back far enough it often stems from someone or some group of people violating this principle from the FCC. To Sum It Up Technology problems are easy to solve. At Linchpin People we help many customers get past the toughest technological challenge – and at the end of the day it is really just a repeatable process of pattern based troubleshooting, logical thinking and starting at the beginning and carefully stepping through to the end. It’s easy at the end of the day. The tough part of what we do as consultants is the people skills. Being able to help get teams working together, being able to help teams take responsibility, to improve team to team communication? That is the difficult part, and we get to use the soft skills on every engagement. Work on professional development (http://professionaldevelopment.sqlpass.org/) and see continuing improvement here, not just with technology. I can teach just about anyone how to be an excellent DBA and performance tuner, but some of these soft skills are much more difficult to teach. If you want to get started with performance analytics and triage of virtualized SQL Servers with the help of experts, read more over at Fix Your SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• How to change Matlab program for solving equation with finite element method?

  - by DSblizzard

  I don't know is this question more related to mathematics or programming and I'm absolute newbie in Matlab. Program FEM_50 applies the finite element method to Laplace's equation -Uxx(x, y) - Uyy(x, y) = F(x, y) in Omega. How to change it to apply FEM to equation -Uxx(x, y) - Uyy(x, y) + U(x, y) = F(x, y)? At this page: http://sc.fsu.edu/~burkardt/m_src/fem_50/fem_50.html additional code files in case you need them. function fem_50 ( ) %% FEM_50 applies the finite element method to Laplace's equation. % % Discussion: % % FEM_50 is a set of MATLAB routines to apply the finite % element method to solving Laplace's equation in an arbitrary % region, using about 50 lines of MATLAB code. % % FEM_50 is partly a demonstration, to show how little it % takes to implement the finite element method (at least using % every possible MATLAB shortcut.) The user supplies datafiles % that specify the geometry of the region and its arrangement % into triangular and quadrilateral elements, and the location % and type of the boundary conditions, which can be any mixture % of Neumann and Dirichlet. % % The unknown state variable U(x,y) is assumed to satisfy % Laplace's equation: % -Uxx(x,y) - Uyy(x,y) = F(x,y) in Omega % with Dirichlet boundary conditions % U(x,y) = U_D(x,y) on Gamma_D % and Neumann boundary conditions on the outward normal derivative: % Un(x,y) = G(x,y) on Gamma_N % If Gamma designates the boundary of the region Omega, % then we presume that % Gamma = Gamma_D + Gamma_N % but the user is free to determine which boundary conditions to % apply. Note, however, that the problem will generally be singular % unless at least one Dirichlet boundary condition is specified. % % The code uses piecewise linear basis functions for triangular elements, % and piecewise isoparametric bilinear basis functions for quadrilateral % elements. % % The user is required to supply a number of data files and MATLAB % functions that specify the location of nodes, the grouping of nodes % into elements, the location and value of boundary conditions, and % the right hand side function in Laplace's equation. Note that the % fact that the geometry is completely up to the user means that % just about any two dimensional region can be handled, with arbitrary % shape, including holes and islands. % clear % % Read the nodal coordinate data file. % load coordinates.dat; % % Read the triangular element data file. % load elements3.dat; % % Read the quadrilateral element data file. % load elements4.dat; % % Read the Neumann boundary condition data file. % I THINK the purpose of the EVAL command is to create an empty NEUMANN array % if no Neumann file is found. % eval ( 'load neumann.dat;', 'neumann=[];' ); % % Read the Dirichlet boundary condition data file. % load dirichlet.dat; A = sparse ( size(coordinates,1), size(coordinates,1) ); b = sparse ( size(coordinates,1), 1 ); % % Assembly. % for j = 1 : size(elements3,1) A(elements3(j,:),elements3(j,:)) = A(elements3(j,:),elements3(j,:)) ... + stima3(coordinates(elements3(j,:),:)); end for j = 1 : size(elements4,1) A(elements4(j,:),elements4(j,:)) = A(elements4(j,:),elements4(j,:)) ... + stima4(coordinates(elements4(j,:),:)); end % % Volume Forces. % for j = 1 : size(elements3,1) b(elements3(j,:)) = b(elements3(j,:)) ... + det( [1,1,1; coordinates(elements3(j,:),:)'] ) * ... f(sum(coordinates(elements3(j,:),:))/3)/6; end for j = 1 : size(elements4,1) b(elements4(j,:)) = b(elements4(j,:)) ... + det([1,1,1; coordinates(elements4(j,1:3),:)'] ) * ... f(sum(coordinates(elements4(j,:),:))/4)/4; end % % Neumann conditions. % if ( ~isempty(neumann) ) for j = 1 : size(neumann,1) b(neumann(j,:)) = b(neumann(j,:)) + ... norm(coordinates(neumann(j,1),:) - coordinates(neumann(j,2),:)) * ... g(sum(coordinates(neumann(j,:),:))/2)/2; end end % % Determine which nodes are associated with Dirichlet conditions. % Assign the corresponding entries of U, and adjust the right hand side. % u = sparse ( size(coordinates,1), 1 ); BoundNodes = unique ( dirichlet ); u(BoundNodes) = u_d ( coordinates(BoundNodes,:) ); b = b - A * u; % % Compute the solution by solving A * U = B for the remaining unknown values of U. % FreeNodes = setdiff ( 1:size(coordinates,1), BoundNodes ); u(FreeNodes) = A(FreeNodes,FreeNodes) \ b(FreeNodes); % % Graphic representation. % show ( elements3, elements4, coordinates, full ( u ) ); return end

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• SQL SERVER – Faster SQL Server Databases and Applications – Power and Control with SafePeak Caching Options

  - by Pinal Dave

  Update: This blog post is written based on the SafePeak, which is available for free download. Today, I’d like to examine more closely one of my preferred technologies for accelerating SQL Server databases, SafePeak. Safepeak’s software provides a variety of advanced data caching options, techniques and tools to accelerate the performance and scalability of SQL Server databases and applications. I’d like to look more closely at some of these options, as some of these capabilities could help you address lagging database and performance on your systems. To better understand the available options, it is best to start by understanding the difference between the usual “Basic Caching” vs. SafePeak’s “Dynamic Caching”. Basic Caching Basic Caching (or the stale and static cache) is an ability to put the results from a query into cache for a certain period of time. It is based on TTL, or Time-to-live, and is designed to stay in cache no matter what happens to the data. For example, although the actual data can be modified due to DML commands (update/insert/delete), the cache will still hold the same obsolete query data. Meaning that with the Basic Caching is really static / stale cache.  As you can tell, this approach has its limitations. Dynamic Caching Dynamic Caching (or the non-stale cache) is an ability to put the results from a query into cache while maintaining the cache transaction awareness looking for possible data modifications. The modifications can come as a result of: DML commands (update/insert/delete), indirect modifications due to triggers on other tables, executions of stored procedures with internal DML commands complex cases of stored procedures with multiple levels of internal stored procedures logic. When data modification commands arrive, the caching system identifies the related cache items and evicts them from cache immediately. In the dynamic caching option the TTL setting still exists, although its importance is reduced, since the main factor for cache invalidation (or cache eviction) become the actual data updates commands. Now that we have a basic understanding of the differences between “basic” and “dynamic” caching, let’s dive in deeper. SafePeak: A comprehensive and versatile caching platform SafePeak comes with a wide range of caching options. Some of SafePeak’s caching options are automated, while others require manual configuration. Together they provide a complete solution for IT and Data managers to reach excellent performance acceleration and application scalability for  a wide range of business cases and applications. Automated caching of SQL Queries: Fully/semi-automated caching of all “read” SQL queries, containing any types of data, including Blobs, XMLs, Texts as well as all other standard data types. SafePeak automatically analyzes the incoming queries, categorizes them into SQL Patterns, identifying directly and indirectly accessed tables, views, functions and stored procedures; Automated caching of Stored Procedures: Fully or semi-automated caching of all read” stored procedures, including procedures with complex sub-procedure logic as well as procedures with complex dynamic SQL code. All procedures are analyzed in advance by SafePeak’s  Metadata-Learning process, their SQL schemas are parsed – resulting with a full understanding of the underlying code, objects dependencies (tables, views, functions, sub-procedures) enabling automated or semi-automated (manually review and activate by a mouse-click) cache activation, with full understanding of the transaction logic for cache real-time invalidation; Transaction aware cache: Automated cache awareness for SQL transactions (SQL and in-procs); Dynamic SQL Caching: Procedures with dynamic SQL are pre-parsed, enabling easy cache configuration, eliminating SQL Server load for parsing time and delivering high response time value even in most complicated use-cases; Fully Automated Caching: SQL Patterns (including SQL queries and stored procedures) that are categorized by SafePeak as “read and deterministic” are automatically activated for caching; Semi-Automated Caching: SQL Patterns categorized as “Read and Non deterministic” are patterns of SQL queries and stored procedures that contain reference to non-deterministic functions, like getdate(). Such SQL Patterns are reviewed by the SafePeak administrator and in usually most of them are activated manually for caching (point and click activation); Fully Dynamic Caching: Automated detection of all dependent tables in each SQL Pattern, with automated real-time eviction of the relevant cache items in the event of “write” commands (a DML or a stored procedure) to one of relevant tables. A default setting; Semi Dynamic Caching: A manual cache configuration option enabling reducing the sensitivity of specific SQL Patterns to “write” commands to certain tables/views. An optimization technique relevant for cases when the query data is either known to be static (like archive order details), or when the application sensitivity to fresh data is not critical and can be stale for short period of time (gaining better performance and reduced load); Scheduled Cache Eviction: A manual cache configuration option enabling scheduling SQL Pattern cache eviction based on certain time(s) during a day. A very useful optimization technique when (for example) certain SQL Patterns can be cached but are time sensitive. Example: “select customers that today is their birthday”, an SQL with getdate() function, which can and should be cached, but the data stays relevant only until 00:00 (midnight); Parsing Exceptions Management: Stored procedures that were not fully parsed by SafePeak (due to too complex dynamic SQL or unfamiliar syntax), are signed as “Dynamic Objects” with highest transaction safety settings (such as: Full global cache eviction, DDL Check = lock cache and check for schema changes, and more). The SafePeak solution points the user to the Dynamic Objects that are important for cache effectiveness, provides easy configuration interface, allowing you to improve cache hits and reduce cache global evictions. Usually this is the first configuration in a deployment; Overriding Settings of Stored Procedures: Override the settings of stored procedures (or other object types) for cache optimization. For example, in case a stored procedure SP1 has an “insert” into table T1, it will not be allowed to be cached. However, it is possible that T1 is just a “logging or instrumentation” table left by developers. By overriding the settings a user can allow caching of the problematic stored procedure; Advanced Cache Warm-Up: Creating an XML-based list of queries and stored procedure (with lists of parameters) for periodically automated pre-fetching and caching. An advanced tool allowing you to handle more rare but very performance sensitive queries pre-fetch them into cache allowing high performance for users’ data access; Configuration Driven by Deep SQL Analytics: All SQL queries are continuously logged and analyzed, providing users with deep SQL Analytics and Performance Monitoring. Reduce troubleshooting from days to minutes with database objects and SQL Patterns heat-map. The performance driven configuration helps you to focus on the most important settings that bring you the highest performance gains. Use of SafePeak SQL Analytics allows continuous performance monitoring and analysis, easy identification of bottlenecks of both real-time and historical data; Cloud Ready: Available for instant deployment on Amazon Web Services (AWS). As you can see, there are many options to configure SafePeak’s SQL Server database and application acceleration caching technology to best fit a lot of situations. If you’re not familiar with their technology, they offer free-trial software you can download that comes with a free “help session” to help get you started. You can access the free trial here. Also, SafePeak is available to use on Amazon Cloud. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Core Concepts – Elasticity, Scalability and ACID Properties – Exploring NuoDB an Elastically Scalable Database System

  - by pinaldave

  I have been recently exploring Elasticity and Scalability attributes of databases. You can see that in my earlier blog posts about NuoDB where I wanted to look at Elasticity and Scalability concepts. The concepts are very interesting, and intriguing as well. I have discussed these concepts with my friend Joyti M and together we have come up with this interesting read. The goal of this article is to answer following simple questions What is Elasticity? What is Scalability? How ACID properties vary from NOSQL Concepts? What are the prevailing problems in the current database system architectures? Why is NuoDB  an innovative and welcome change in database paradigm? Elasticity This word’s original form is used in many different ways and honestly it does do a decent job in holding things together over the years as a person grows and contracts. Within the tech world, and specifically related to software systems (database, application servers), it has come to mean a few things - allow stretching of resources without reaching the breaking point (on demand). What are resources in this context? Resources are the usual suspects – RAM/CPU/IO/Bandwidth in the form of a container (a process or bunch of processes combined as modules). When it is about increasing resources the simplest idea which comes to mind is the addition of another container. Another container means adding a brand new physical node. When it is about adding a new node there are two questions which comes to mind. 1) Can we add another node to our software system? 2) If yes, does adding new node cause downtime for the system? Let us assume we have added new node, let us see what the new needs of the system are when a new node is added. Balancing incoming requests to multiple nodes Synchronization of a shared state across multiple nodes Identification of “downstate” and resolution action to bring it to “upstate” Well, adding a new node has its advantages as well. Here are few of the positive points Throughput can increase nearly horizontally across the node throughout the system Response times of application will increase as in-between layer interactions will be improved Now, Let us put the above concepts in the perspective of a Database. When we mention the term “running out of resources” or “application is bound to resources” the resources can be CPU, Memory or Bandwidth. The regular approach to “gain scalability” in the database is to look around for bottlenecks and increase the bottlenecked resource. When we have memory as a bottleneck we look at the data buffers, locks, query plans or indexes. After a point even this is not enough as there needs to be an efficient way of managing such large workload on a “single machine” across memory and CPU bound (right kind of scheduling)  workload. We next move on to either read/write separation of the workload or functionality-based sharing so that we still have control of the individual. But this requires lots of planning and change in client systems in terms of knowing where to go/update/read and for reporting applications to “aggregate the data” in an intelligent way. What we ideally need is an intelligent layer which allows us to do these things without us getting into managing, monitoring and distributing the workload. Scalability In the context of database/applications, scalability means three main things Ability to handle normal loads without pressure E.g. X users at the Y utilization of resources (CPU, Memory, Bandwidth) on the Z kind of hardware (4 processor, 32 GB machine with 15000 RPM SATA drives and 1 GHz Network switch) with T throughput Ability to scale up to expected peak load which is greater than normal load with acceptable response times Ability to provide acceptable response times across the system E.g. Response time in S milliseconds (or agreed upon unit of measure) – 90% of the time The Issue – Need of Scale In normal cases one can plan for the load testing to test out normal, peak, and stress scenarios to ensure specific hardware meets the needs. With help from Hardware and Software partners and best practices, bottlenecks can be identified and requisite resources added to the system. Unfortunately this vertical scale is expensive and difficult to achieve and most of the operational people need the ability to scale horizontally. This helps in getting better throughput as there are physical limits in terms of adding resources (Memory, CPU, Bandwidth and Storage) indefinitely. Today we have different options to achieve scalability: Read & Write Separation The idea here is to do actual writes to one store and configure slaves receiving the latest data with acceptable delays. Slaves can be used for balancing out reads. We can also explore functional separation or sharing as well. We can separate data operations by a specific identifier (e.g. region, year, month) and consolidate it for reporting purposes. For functional separation the major disadvantage is when schema changes or workload pattern changes. As the requirement grows one still needs to deal with scale need in manual ways by providing an abstraction in the middle tier code. Using NOSQL solutions The idea is to flatten out the structures in general to keep all values which are retrieved together at the same store and provide flexible schema. The issue with the stores is that they are compromising on mostly consistency (no ACID guarantees) and one has to use NON-SQL dialect to work with the store. The other major issue is about education with NOSQL solutions. Would one really want to make these compromises on the ability to connect and retrieve in simple SQL manner and learn other skill sets? Or for that matter give up on ACID guarantee and start dealing with consistency issues? Hybrid Deployment – Mac, Linux, Cloud, and Windows One of the challenges today that we see across On-premise vs Cloud infrastructure is a difference in abilities. Take for example SQL Azure – it is wonderful in its concepts of throttling (as it is shared deployment) of resources and ability to scale using federation. However, the same abilities are not available on premise. This is not a mistake, mind you – but a compromise of the sweet spot of workloads, customer requirements and operational SLAs which can be supported by the team. In today’s world it is imperative that databases are available across operating systems – which are a commodity and used by developers of all hues. An Ideal Database Ability List A system which allows a linear scale of the system (increase in throughput with reasonable response time) with the addition of resources A system which does not compromise on the ACID guarantees and require developers to learn new paradigms A system which does not force fit a new way interacting with database by learning Non-SQL dialect A system which does not force fit its mechanisms for providing availability across its various modules. Well NuoDB is the first database which has all of the above abilities and much more. In future articles I will cover my hands-on experience with it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: NuoDB

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• How to get full control of umask/PAM/permissions?

  - by plua

  OUR SITUATION Several people from our company log in to a server and upload files. They all need to be able to upload and overwrite the same files. They have different usernames, but are all part of the same group. However, this is an internet server, so the "other" users should have (in general) just read-only access. So what I want to have is these standard permissions: files: 664 directories: 771 My goal is that all users do not need to worry about permissions. The server should be configured in such a way that these permissions apply to all files and directories, newly created, copied, or over-written. Only when we need some special permissions we'd manually change this. We upload files to the server by SFTP-ing in Nautilus, by mounting the server using sshfs and accessing it in Nautilus as if it were a local folder, and by SCP-ing in the command line. That basically covers our situation and what we aim to do. Now, I have read many things about the beautiful umask functionality. From what I understand umask (together with PAM) should allow me to do exactly what I want: set standard permissions for new files and directories. However, after many many hours of reading and trial-and-error, I still do not get this to work. I get many unexpected results. I really like to get a solid grasp of umask and have many question unanswered. I will post these questions below, together with my findings and an explanation of my trials that led to these questions. Given that many things appear to go wrong, I think that I am doing several things wrong. So therefore, there are many questions. NOTE: I am using Ubuntu 9.10 and therefore can not change the sshd_config to set the umask for the SFTP server. Installed SSH OpenSSH_5.1p1 Debian-6ubuntu2 < required OpenSSH 5.4p1. So here go the questions. 1. DO I NEED TO RESTART FOR PAM CHANGS TO TAKE EFFECT? Let's start with this. There were so many files involved and I was unable to figure out what does and what does not affect things, also because I did not know whether or not I have to restart the whole system for PAM changes to take effect. I did do so after not seeing the expected results, but is this really necessary? Or can I just log out from the server and log back in, and should new PAM policies be effective? Or is there some 'PAM' program to reload? 2. IS THERE ONE SINGLE FILE TO CHANGE THAT AFFECTS ALL USERS FOR ALL SESSIONS? So I ended up changing MANY files, as I read MANY different things. I ended up setting the umask in the following files: ~/.profile -> umask=0002 ~/.bashrc -> umask=0002 /etc/profile -> umask=0002 /etc/pam.d/common-session -> umask=0002 /etc/pam.d/sshd -> umask=0002 /etc/pam.d/login -> umask=0002 I want this change to apply to all users, so some sort of system-wide change would be best. Can it be achieved? 3. AFTER ALL, THIS UMASK THING, DOES IT WORK? So after changing umask to 0002 at every possible place, I run tests. ------------SCP----------- TEST 1: scp testfile (which has 777 permissions for testing purposes) server:/home/ testfile 100% 4 0.0KB/s 00:00 Let's check permissions: user@server:/home$ ls -l total 4 -rwx--x--x 1 user uploaders 4 2011-02-05 17:59 testfile (711) ---------SSH------------ TEST 2: ssh server user@server:/home$ touch anotherfile user@server:/home$ ls -l total 4 -rw-rw-r-- 1 user uploaders 0 2011-02-05 18:03 anotherfile (664) --------SFTP----------- Nautilus: sftp://server/home/ Copy and paste newfile from client to server (777 on client) TEST 3: user@server:/home$ ls -l total 4 -rwxrwxrwx 1 user uploaders 3 2011-02-05 18:05 newfile (777) Create a new file through Nautilus. Check file permissions in terminal: TEST 4: user@server:/home$ ls -l total 4 -rw------- 1 user uploaders 0 2011-02-05 18:06 newfile (600) I mean... WHAT just happened here?! We should get 644 every single time. Instead I get 711, 777, 600, and then once 644. And the 644 is only achieved when creating a new, blank file through SSH, which is the least probable scenario. So I am asking, does umask/pam work after all? 4. SO WHAT DOES IT MEAN TO UMASK SSHFS? Sometimes we mount a server locally, using sshfs. Very useful. But again, we have permissions issues. Here is how we mount: sshfs -o idmap=user -o umask=0113 user@server:/home/ /mnt NOTE: we use umask = 113 because apparently, sshfs starts from 777 instead of 666, so with 113 we get 664 which is the desired file permission. But what now happens is that we see all files and directories as if they are 664. We browse in Nautilus to /mnt and: Right click - New File (newfile) --- TEST 5 Right click - New Folder (newfolder) --- TEST 6 Copy and paste a 777 file from our local client --- TEST 7 So let's check on the command line: user@client:/mnt$ ls -l total 8 -rw-rw-r-- 1 user 1007 3 Feb 5 18:05 copyfile (664) -rw-rw-r-- 1 user 1007 0 Feb 5 18:15 newfile (664) drw-rw-r-- 1 user 1007 4096 Feb 5 18:15 newfolder (664) But hey, let's check this same folder on the server-side: user@server:/home$ ls -l total 8 -rwxrwxrwx 1 user uploaders 3 2011-02-05 18:05 copyfile (777) -rw------- 1 user uploaders 0 2011-02-05 18:15 newfile (600) drwx--x--x 2 user uploaders 4096 2011-02-05 18:15 newfolder (711) What?! The REAL file permissions are very different from what we see in Nautilus. So does this umask on sshfs just create a 'filter' that shows unreal file permissions? And I tried to open a file from another user but the same group that had real 600 permissions but 644 'fake' permissions, and I could still not read this, so what good is this filter?? 5. UMASK IS ALL ABOUT FILES. BUT WHAT ABOUT DIRECTORIES? From my tests I can see that the umask that is being applied also somehow influences the directory permissions. However, I want my files to be 664 (002) and my directories to be 771 (006). So is it possible to have a different umask for directories? 6. PERHAPS UMASK/PAM IS REALLY COOL, BUT UBUNTU IS JUST BUGGY? On the one hand, I have read topics of people that have had success with PAM/UMASK and Ubuntu. On the other hand, I have found many older and newer bugs regarding umask/PAM/fuse on Ubuntu: https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/241198 https://bugs.launchpad.net/ubuntu/+source/fuse/+bug/239792 https://bugs.launchpad.net/ubuntu/+source/pam/+bug/253096 https://bugs.launchpad.net/ubuntu/+source/sudo/+bug/549172 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=314796 So I do not know what to believe anymore. Should I just give up? Would ACL solve all my problems? Or do I have again problems using Ubuntu? One word of caution with backups using tar. Red Hat /Centos distributions support acls in the tar program but Ubuntu does not support acls when backing up. This means that all acls will be lost when you create a backup. I am very willing to upgrade to Ubuntu 10.04 if that would solve my problems too, but first I want to understand what is happening.

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• Cost Comparison Hard Disk Drive to Solid State Drive on Price per Gigabyte - dispelling a myth!

  - by tonyrogerson

  It is often said that Hard Disk Drive storage is significantly cheaper per GiByte than Solid State Devices – this is wholly inaccurate within the database space. People need to look at the cost of the complete solution and not just a single component part in isolation to what is really required to meet the business requirement. Buying a single Hitachi Ultrastar 600GB 3.5” SAS 15Krpm hard disk drive will cost approximately £239.60 (http://scan.co.uk, 22nd March 2012) compared to an OCZ 600GB Z-Drive R4 CM84 PCIe costing £2,316.54 (http://scan.co.uk, 22nd March 2012); I’ve not included FusionIO ioDrive because there is no public pricing available for it – something I never understand and personally when companies do this I immediately think what are they hiding, luckily in FusionIO’s case the product is proven though is expensive compared to OCZ enterprise offerings. On the face of it the single 15Krpm hard disk has a price per GB of £0.39, the SSD £3.86; this is what you will see in the press and this is what sales people will use in comparing the two technologies – do not be fooled by this bullshit people! What is the requirement? The requirement is the database will have a static size of 400GB kept static through archiving so growth and trim will balance the database size, the client requires resilience, there will be several hundred call centre staff querying the database where queries will read a small amount of data but there will be no hot spot in the data so the randomness will come across the entire 400GB of the database, estimates predict that the IOps required will be approximately 4,000IOps at peak times, because it’s a call centre system the IO latency is important and must remain below 5ms per IO. The balance between read and write is 70% read, 30% write. The requirement is now defined and we have three of the most important pieces of the puzzle – space required, estimated IOps and maximum latency per IO. Something to consider with regard SQL Server; write activity requires synchronous IO to the storage media specifically the transaction log; that means the write thread will wait until the IO is completed and hardened off until the thread can continue execution, the requirement has stated that 30% of the system activity will be write so we can expect a high amount of synchronous activity. The hardware solution needs to be defined; two possible solutions: hard disk or solid state based; the real question now is how many hard disks are required to achieve the IO throughput, the latency and resilience, ditto for the solid state. Hard Drive solution On a test on an HP DL380, P410i controller using IOMeter against a single 15Krpm 146GB SAS drive, the throughput given on a transfer size of 8KiB against a 40GiB file on a freshly formatted disk where the partition is the only partition on the disk thus the 40GiB file is on the outer edge of the drive so more sectors can be read before head movement is required: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 3,733 IOps at an average latency of 34.06ms (34 MiB/s). The same test was done on the same disk but the test file was 130GiB: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 528 IOps at an average latency of 217.49ms (4 MiB/s). From the result it is clear random performance gets worse as the disk fills up – I’m currently writing an article on short stroking which will cover this in detail. Given the work load is random in nature looking at the random performance of the single drive when only 40 GiB of the 146 GB is used gives near the IOps required but the latency is way out. Luckily I have tested 6 x 15Krpm 146GB SAS 15Krpm drives in a RAID 0 using the same test methodology, for the same test above on a 130 GiB for each drive added the performance boost is near linear, for each drive added throughput goes up by 5 MiB/sec, IOps by 700 IOps and latency reducing nearly 50% per drive added (172 ms, 94 ms, 65 ms, 47 ms, 37 ms, 30 ms). This is because the same 130GiB is spread out more as you add drives 130 / 1, 130 / 2, 130 / 3 etc. so implicit short stroking is occurring because there is less file on each drive so less head movement required. The best latency is still 30 ms but we have the IOps required now, but that’s on a 130GiB file and not the 400GiB we need. Some reality check here: a) the drive randomness is more likely to be 50/50 and not a full 100% but the above has highlighted the effect randomness has on the drive and the more a drive fills with data the worse the effect. For argument sake let us assume that for the given workload we need 8 disks to do the job, for resilience reasons we will need 16 because we need to RAID 1+0 them in order to get the throughput and the resilience, RAID 5 would degrade performance. Cost for hard drives: 16 x £239.60 = £3,833.60 For the hard drives we will need disk controllers and a separate external disk array because the likelihood is that the server itself won’t take the drives, a quick spec off DELL for a PowerVault MD1220 which gives the dual pathing with 16 disks 146GB 15Krpm 2.5” disks is priced at £7,438.00, note its probably more once we had two controller cards to sit in the server in, racking etc. Minimum cost taking the DELL quote as an example is therefore: {Cost of Hardware} / {Storage Required} £7,438.60 / 400 = £18.595 per GB £18.59 per GiB is a far cry from the £0.39 we had been told by the salesman and the myth. Yes, the storage array is composed of 16 x 146 disks in RAID 10 (therefore 8 usable) giving an effective usable storage availability of 1168GB but the actual storage requirement is only 400 and the extra disks have had to be purchased to get the  IOps up. Solid State Drive solution A single card significantly exceeds the IOps and latency required, for resilience two will be required. ( £2,316.54 * 2 ) / 400 = £11.58 per GB With the SSD solution only two PCIe sockets are required, no external disk units, no additional controllers, no redundant controllers etc. Conclusion I hope by showing you an example that the myth that hard disk drives are cheaper per GiB than Solid State has now been dispelled - £11.58 per GB for SSD compared to £18.59 for Hard Disk. I’ve not even touched on the running costs, compare the costs of running 18 hard disks, that’s a lot of heat and power compared to two PCIe cards!Just a quick note: I've left a fair amount of information out due to this being a blog! If in doubt, email me :)I'll also deal with the myth that SSD's wear out at a later date as well - that's just way over done still, yes, 5 years ago, but now - no.

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• Error 324 (net::ERR_EMPTY_RESPONSE): Unknown error.

  - by Kp

  I get the following error in Chrome every time I try to run my script on a Linux server: Error 324 (net::ERR_EMPTY_RESPONSE): Unknown error. In Firefox it just shows a blank white page. Whenever I run it on my local test server (IIS on Windows 7) it runs exactly the way it should with no errors. I am pretty sure that it is a problem with the imap_open function. error_reporting(E_ALL); echo "test"; // enter gmail username below e.g.-- $m_username = "yourusername"; $m_username = "username"; // enter gmail password below e.g.-- $m_password = "yourpword"; $m_password = "password"; // Enter the mail server to connect to $server = '{imap.gmail.com:993/imap/ssl/novalidate-cert}INBOX'; // enter the number of unread messages you want to display from mailbox or //enter 0 to display all unread messages e.g.-- $m_acs = 0; $m_acs = 10; // How far back in time do you want to search for unread messages - one month = 0 , two weeks = 1, one week = 2, three days = 3, // one day = 4, six hours = 5 or one hour = 6 e.g.-- $m_t = 6; $m_t = 2; //-----------Nothing More to edit below //open mailbox $m_mail = imap_open ($server, $m_username . "@gmail.com", $m_password) // or throw an error or die("ERROR: " . imap_last_error()); // unix time gone by $m_gunixtp = array(2592000, 1209600, 604800, 259200, 86400, 21600, 3600); // Date to start search $m_gdmy = date('d-M-Y', time() - $m_gunixtp[$m_t]); //search mailbox for unread messages since $m_t date $m_search=imap_search ($m_mail, 'ALL'); // Order results starting from newest message rsort($m_search); //if m_acs 0 then limit results if($m_acs 0){ array_splice($m_search, $m_acs); } $read = $_GET[read]; if ($read) { function get_mime_type(&$structure) { $primary_mime_type = array("TEXT", "MULTIPART","MESSAGE", "APPLICATION", "AUDIO","IMAGE", "VIDEO", "OTHER"); if($structure-subtype) { return $primary_mime_type[(int) $structure-type] . '/' .$structure-subtype; } return "TEXT/PLAIN"; } function get_part($stream, $msg_number, $mime_type, $structure = false,$part_number = false) { if(!$structure) { $structure = imap_fetchstructure($stream, $msg_number); } if($structure) { if($mime_type == get_mime_type($structure)) { if(!$part_number) { $part_number = "1"; } $text = imap_fetchbody($stream, $msg_number, $part_number); if($structure->encoding == 3) { return imap_base64($text); } else if($structure->encoding == 4) { return imap_qprint($text); } else { return $text; } } if($structure->type == 1) /* multipart */ { while(list($index, $sub_structure) = each($structure->parts)) { if($part_number) { $prefix = $part_number . '.'; } $data = get_part($stream, $msg_number, $mime_type, $sub_structure,$prefix . ($index + 1)); if($data) { return $data; } } // END OF WHILE } // END OF MULTIPART } // END OF STRUTURE return false; } // END OF FUNCTION // GET TEXT BODY $dataTxt = get_part($m_mail, $read, "TEXT/PLAIN"); // GET HTML BODY $dataHtml = get_part($m_mail, $read, "TEXT/HTML"); if ($dataHtml != "") { $msgBody = $dataHtml; $mailformat = "html"; } else { $msgBody = ereg_replace("\n","",$dataTxt); $mailformat = "text"; } if ($mailformat == "text") { echo "<html><head><title>Messagebody</title></head><body bgcolor=\"white\">$msgBody</body></html>"; } else { echo $msgBody; // It contains all HTML HEADER tags so we don't have to make them. } exit; } //loop it foreach ($m_search as $what_ever) { //get imap header info for obj thang $obj_thang = imap_headerinfo($m_mail, $what_ever); //get body info for obj thang $obj_thangs = imap_body($m_mail, $what_ever); //Then spit it out below.........if you dont swallow echo "Message ID# " . $what_ever . " Date: " . date("F j, Y, g:i a", $obj_thang-udate) . " From: " . $obj_thang-fromaddress . " To: " . $obj_thang-toaddress . " Subject: " . $obj_thang-Subject . " "; } echo "" . $m_empty . ""; //close mailbox imap_close($m_mail); ?

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