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• PHP - Internal APIs/Libraries - What makes sense?

  - by Mark Locker

  I've been having a discussion lately with some colleagues about the best way to approach a new project, and thought it'd be interesting to get some external thoughts thrown into the mix. Basically, we're redeveloping a fairly large site (written in PHP) and have differing opinions on how the platform should be setup. Requirements: The platform will need to support multiple internal websites, as well as external (non-PHP) projects which at the moment consist of a mobile app and a toolbar. We have no plans/need in the foreseeable future to open up an API externally (for use in products other than our own). My opinion: We should have a library of well documented native model classes which can be shared between projects. These models will represent everything in our database and can take advantage of object orientated features such as inheritance, traits, magic methods, etc. etc. As well as employing ORM. We can then add an API layer on top of these models which can basically accept requests and route them to the appropriate methods, translating the response so that it can be used platform independently. This routing for each method can be setup as and when it's required. Their opinion: We should have a single HTTP API which is used by all projects (internal PHP ones or otherwise). My thoughts: To me, there are a number of issues with using the sole HTTP API approach: It will be very expensive performance wise. One page request will result in several additional http requests (which although local, are still ones that Apache will need to handle). You'll lose all of the best features PHP has for OO development. From simple inheritance, to employing the likes of ORM which can save you writing a lot of code. For internal projects, the actual process makes me cringe. To get a users name, for example, a request would go out of our box, over the LAN, back in, then run through a script which calls a method, JSON encodes the output and feeds that back. That would then need to be JSON decoded, and be presented as an array ready to use. Working with arrays, as appose to objects, makes me sad in a modern PHP framework. Their thoughts (and my responses): Having one method of doing thing keeps things simple. - You'd only do things differently if you were using a different language anyway. It will become robust. - Seeing as the API will run off the library of models, I think my option would be just as robust. What do you think? I'd be really interested to hear the thoughts of others on this, especially as opinions on both sides are not founded on any past experience.

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• Advantages to Multiple Methods over Switch

  - by tandu

  I received a code review from a senior developer today asking "By the way, what is your objection to dispatching functions by way of a switch statement?" I have read in many places about how pumping an argument through switch to call methods is bad OOP, not as extensible, etc. However, I can't really come up with a definitive answer for him. I would like to settle this for myself once and for all. Here are our competing code suggestions (php used as an example, but can apply more universally): class Switch { public function go($arg) { switch ($arg) { case "one": echo "one\n"; break; case "two": echo "two\n"; break; case "three": echo "three\n"; break; default: throw new Exception("Unknown call: $arg"); break; } } } class Oop { public function go_one() { echo "one\n"; } public function go_two() { echo "two\n"; } public function go_three() { echo "three\n"; } public function __call($_, $__) { throw new Exception("Unknown call $_ with arguments: " . print_r($__, true)); } } Part of his argument was "It (switch method) has a much cleaner way of handling default cases than what you have in the generic __call() magic method." I disagree about the cleanliness and in fact prefer call, but I would like to hear what others have to say. Arguments I can come up with in support of Oop scheme: A bit cleaner in terms of the code you have to write (less, easier to read, less keywords to consider) Not all actions delegated to a single method. Not much difference in execution here, but at least the text is more compartmentalized. In the same vein, another method can be added anywhere in the class instead of a specific spot. Methods are namespaced, which is nice. Does not apply here, but consider a case where Switch::go() operated on a member rather than a parameter. You would have to change the member first, then call the method. For Oop you can call the methods independently at any time. Arguments I can come up with in support of Switch scheme: For the sake of argument, cleaner method of dealing with a default (unknown) request Seems less magical, which might make unfamiliar developers feel more comfortable Anyone have anything to add for either side? I'd like to have a good answer for him.

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• How best to look up objects by label?

  - by dsollen

  I am writing the server backed by a pre-written API. I'm going to get a number of strings representing ports, signals, paths, etc etc etc. I need to look up the object associated with a given label, these objects are all in memory (no sql magic to do this for me). My question is, how best do I associate a given unique label with the mutable object it represents? I have enough objects that looking through every signal or every port to find the one that matches is possible, but may be slightly too slow. To be honest the direct 'look at every object' method is probably good enough for so small a body of objects and anything else is premature optimization, but I still am curious what the proper solution would be if I thought my signals were going to grow a bit larger. As I see it there are two options available. First would be to to create a 'store' that is a simple map between object and label. I could have it so that every time I call addObject the object is automatically saved into a hashmap or the like. This works, but relies on my properly adding and deleting each object so the map doesn't grow indefinitely. The biggest issue to me is that this involves having some hidden static map in my ModelObject class that just feels...wrong somehow. The other option is to have some method that can interpret the labels. All of these labels are derived from the underlying objects. So I can look at the signal label, for instance, and say "these 20 characters are the port" to figure out what port I need. This would allow me to quickly figure out what I need. However, if the label method is changed the translateLabelToObject method needs to be updated as well or everything breaks. Which solution is cleaner, or possibly a cleaner solution than either of above? For the record I'm working with sufficient number of variables to make direct comparison a little slow, but not enough to be concerned about memory overhead, written in java. All objects that have labels I need to look up extend the same parent class.

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• URL slugs: ideal length, and the real SEO effects of these slugs

  - by tattvamasi

  this question is addressed widely on SO and outside it, but for some reason, instead of taking it as a good load of great advice, all this information is confusing me. ** Problem ** I already had, on one of my sites, "prettified" urls. I had taken out the query strings, rewritten the URLS, and the link was short enough for me, but had a problem: the ID of the item or post in the URL isn't good for users. One of the users asked is there's a way to get rid of numbers, and I thought it was better for users to just see a clue of the page content in the URL. ** Solution ** With this in mind, I am trying with a section of the site.Armed with 301 redirects, some parsing work, and a lot of patience, I have added the URL slugs to some blog entries, and the slug of the URL reports the title of the article (something close to http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ ** Problems after Solution ** The problem, as I see it, is that now the URL of those blog articles is very descriptive for sure, but it is also impossible to remember. So, this brings me to the same issue I had with my previous problem: if numbers say nothing and can't be remembered, what's the use of these slugs? I prefer to see http://example.com/my-news/1/ than http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ To avoid forcing my user to memorize my URLS, I have added a script that finds the closest match to the URL you type, and redirects there. This is something I like, because the page now acts as a sort of little search engine, and users can play with the URLS to find articles. ** Open questions ** I still have some open questions, and don't seem to be able to find an answer, because answers tend to contradict one another. 1) How many characters should an URL ideally be long? I've read the magic number 115 and am sticking to that, but am not sure. 2) Is this really good for SEO? One of those blog articles I have redirected, with ID number in the URL and all, ranked second on Google. I've just found this question, and the answer seems to be consistent with what I think URL slug and SEO - structure (but see this other question with the opposite opinion) 3) To make a question with a specific example, would this URL risk to be penalized? Is it acceptable? Is it too long? StackOverflow seems to have comparably long URLs, but I'm not sure it's a winning strategy in my case. I just wanted to facilitate my users without running into Google's algorithms.

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• Can my machine run Ubuntu( kubuntu | xubuntu | mint ) 12.04 WELL?

  - by Steve

  I have a 9 year old computer packing the hardware listed below. My question is, can I run 12.04 ( Ubuntu, Kubuntu, MINT or Xubuntu ) WELL? I was running Ubuntu 10.10 and I upgraded to 12.04 by going through each release via the update manager: 11.04 - 11.10 -12.04 During the installation process for 12.04 I saw an error message that there was an error installing and setting up part of the kernel. Later, when I tried installing a package in synaptic, I got another error message mentioning the kernel. When I rebooted, I got told somehting about my video and graphics was not configured properly and that I would have to do it manually ( like I know ). It gave me the option to enter the system in low graphics mode, but it just hanged. I had an old livecd of Xubuntu 10.10 around so I used that to get into my computer and copy data over to an external hard drive. I think tried to install Xubuntu 10.10 from the livecd, with the option "download updates" checked. The install process moved along a bit, then halted for about 5 hours. I rebooted my machine and tried the Xubuntu 10.10 installer WITHOUT the option to "download updates". The install completed in about 15 minutes. So, all of that is making me wonder if there is someting about 12.04 that does not like my hardware. I'm willing to try again, but only if I know I will not have to spend hours just to get to an error message and a hosed up system like I did last night. I also think I have a lot more RAM than is being reported in the output below. I had extra ram installed last year. I'm not good with the command line readouts, but there seems like there should be a lot more. I wasn't thrilled with Unity. I am willing to try Kubuntu 12.04. Will I run into the same problems? What is the highest version of a *ubuntu can I upgrade to? Thanks CPU Model: Intel(R) Pentium(R) 4 CPU 2.53GHz Frequency: 2533.223 MHz L2 Cache: 512 KB Bogomips: 5066.44 Numbering: family(15) model(2) stepping(7) Flags: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up pebs bts cid RAM ~$ free -mt total used free shared buffers cached Mem: 1506 891 615 0 91 521 -/+ buffers/cache: 278 1227 Swap: 1609 0 1609 Total: 3116 891 2225 Video Card 01:00.0 VGA compatible controller: nVidia Corporation NV18 [GeForce4 MX 440 AGP 8x] (rev a2) (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. V9180 Magic Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 16 Memory at fd000000 (32-bit, non-prefetchable) [size=16M] Memory at f0000000 (32-bit, prefetchable) [size=64M] Expansion ROM at fe9e0000 [disabled] [size=128K] Kernel driver in use: nouveau Kernel modules: nouveau, nvidiafb Motherboard Intel 845PE ATX 533FSB DDR333 USB2

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• Imperative vs. component based programming [closed]

  - by AlexW

  I've been thinking about how programming and more specifically the teaching of programming is advocated amongst the community (online). Often I've heard that Ruby and RoR is an ideal platform for learning to program. I completely disagree... RoR and Ruby are based on the application of the component based paradigm, which means they are ideal for rapid application development. This is much like the MVC model in PHP and ASP.NET But, learning a proper imperative language like Java or C/C++ (or even Perl and PHP) is the only way for a new programmer to explore logic itself, and not get too bogged down in architectural concerns like the need for separation of concerns, and the preference for components. Maybe it's a personal preference thing. I rather think that the most interesting aspects to programming are the procedural bits of code I write that actually do stuff rather than the project planning, and modelling that comes about from fully object oriented engineering or simply using the MVC model. I know this may sound confused to some of you. I feel strongly though that the best way for programming to be taught is through imperative and procedural methods. Architectural (component) methods come later, if at all. After all, none of the amazing algorithms that exist were based on OOP practice! It's all procedural code when it comes to the 'magic'. OOP is useful in creating products and utilities. Algorithms are what makes things happen, and move data around, and so imperative (and/or procedural) code are what matters most. When I see programmers recommending Ruby on Rails to newbie developers, I think it's just so wrong. Just because you write less code with Ruby does not make it easier to do! It's the opposite... you have to know loads more to appreciate its succinct nature. New coders who really want to understand the nuts and bolts of coding need to go away and figure out writing methods/functions (i.e. imperative programming) and working in procedural style, in order to grasp the fundamentals, first, before looking into architectural ways of working. So, my question is: should Ruby ever be recommended as a first language? I think no (obviously)... what arguments are there for it?

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• Getting a SecurityToken from a RequestSecurityTokenResponse in WIF

  - by Shawn Cicoria

  When you’re working with WIF and WSTrustChannelFactory when you call the Issue operation, you can also request that a RequestSecurityTokenResponse as an out parameter. However, what can you do with that object?  Well, you could keep it around and use it for subsequent calls with the extension method CreateChannelWithIssuedToken – or can you? public static T CreateChannelWithIssuedToken<T>(this ChannelFactory<T> factory, SecurityToken issuedToken);   As you can see from the method signature it takes a SecurityToken – but that’s not present on the RequestSecurityTokenResponse class. However, you can through a little magic get a GenericXmlSecurityToken by means of the following set of extension methods below – just call rstr.GetSecurityTokenFromResponse() – and you’ll get a GenericXmlSecurityToken as a return. public static class TokenHelper { /// <summary> /// Takes a RequestSecurityTokenResponse, pulls out the GenericXmlSecurityToken usable for further WS-Trust calls /// </summary> /// <param name="rstr"></param> /// <returns></returns> public static GenericXmlSecurityToken GetSecurityTokenFromResponse(this RequestSecurityTokenResponse rstr) { var lifeTime = rstr.Lifetime; var appliesTo = rstr.AppliesTo.Uri; var tokenXml = rstr.GetSerializedTokenFromResponse(); var token = GetTokenFromSerializedToken(tokenXml, appliesTo, lifeTime); return token; } /// <summary> /// Provides a token as an XML string. /// </summary> /// <param name="rstr"></param> /// <returns></returns> public static string GetSerializedTokenFromResponse(this RequestSecurityTokenResponse rstr) { var serializedRst = new WSFederationSerializer().GetResponseAsString(rstr, new WSTrustSerializationContext()); return serializedRst; } /// <summary> /// Turns the XML representation of the token back into a GenericXmlSecurityToken. /// </summary> /// <param name="tokenAsXmlString"></param> /// <param name="appliesTo"></param> /// <param name="lifetime"></param> /// <returns></returns> public static GenericXmlSecurityToken GetTokenFromSerializedToken(this string tokenAsXmlString, Uri appliesTo, Lifetime lifetime) { RequestSecurityTokenResponse rstr2 = new WSFederationSerializer().CreateResponse( new SignInResponseMessage(appliesTo, tokenAsXmlString), new WSTrustSerializationContext()); return new GenericXmlSecurityToken( rstr2.RequestedSecurityToken.SecurityTokenXml, new BinarySecretSecurityToken( rstr2.RequestedProofToken.ProtectedKey.GetKeyBytes()), lifetime.Created.HasValue ? lifetime.Created.Value : DateTime.MinValue, lifetime.Expires.HasValue ? lifetime.Expires.Value : DateTime.MaxValue, rstr2.RequestedAttachedReference, rstr2.RequestedUnattachedReference, null); } }

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• FTP Error: 550 Cant change directory to /: Permission denied

  - by Alessandro Merletti de Palo

  I installed Pureftpd and Ispconfig3 on my server. Starting from the point I'll probably uninstall ispconfig3 and make things directly on the server, now I am so stubborn I really want to see where's the problem. I created a ftp user through ispconfig, named amdpftp. It is related to a server user named web7. It logs in with username and password, but if i try to ls, it tells me: FTP Error: 550 Cant change directory to /: Permission denied I thought many things, like: 1. It is a problem of permissions. I went to /var/www/clients/client0/web7 , it was immutable and owned by root. Chattr -i and chown web7:client0 changed permissions, but with no effect. I restored to root:root, and made it immutable again. 2. I make some mistakes in the pureftpd installation: Wrong, it works pretty fine. The pureftpd.log doesn't seem to say anything bad. 3. The pureftpd.log file is only the pureftpd one, I should also check the mysqld functionality, as it is in a mysql database that user, password and working directory are stored. I enabled logging in the my.cnf, but also in the ispconfig database operation there wasn't anything wrong. Then I mkdir testftp in /var/www, chown web7:client0, and edited amdpftp user root directory from /var/www/clients/client0/web7 into /var/www/testftp . Guess what? It worked. So, now I know: 1. The PureFtpd works pretty fine 2. The mysql ispconfig database as well 3. The username and password of the virtual user created by ispconfig into pureftpd work 4. The correlation between username and password and the user web7 and the group client0 does work. What kind of magic has been cast upon the ispconfig directories [/var/www/clients/*] that block ftpusers to operate?

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• Install a web certificate on an Android device

  - by martani_net

  To gain access to WIFI at university I have to login with my user/pass credentials. The certificate of their website (the local home page that asks for the credentials) is not recognized as a trusted certificate, so we install it separately on our computers. The problem is that I don't take my laptop with me often to university, so I usually want to connect using my HTC Magic, but I have no clue on how to install the certificate separately on Android, it is always rejected. [Edit2] : this is what is stated in their website Need for installation of official certificates CyberTrust validated by the CRU (http://www.cru.fr/wiki/scs/) The certificates contain information certified to generate encryption keys for data exchange, called "sensitive" as the password of a user. By connecting to CanalIP-UPMC, for example, the user must validate the identity of the server accepting the certificate appears on the screen in a "popup window". In reality, the user is unable to validate a certificate knowing, because a simple visual check of the license is impossible. Therefore, the certificates of the certification authority (CRU-Cybertrust Educationnal-ca.ca Cybertrust and-global-root-ca.ca) must be installed prior to the browser for the validity of the certificate server can be controlled automatically. Before you connect to the network-UPMC CanalIP you must register in your browser through the certification authority Cybertrust-Educationnal-ca.ca Download the Cybertrust-Educationnal-ca.ca, depending on your browser and select the link below : With Internet Explorer, click on the link following. With Firefox, click on the link following. With Safari, click the link following. If this procedure is not respected, a real risk is incurred by the user: that of being robbed password LDAP directory UPMC. A malicious server may in fact try very easily attack type "man-in-the-middle" by posing as the legitimate server at UPMC. The theft of a password allows the attacker to steal an identity for transactions over the Internet can engage the responsibility of the user trapped ... This is their website : http://www.canalip.upmc.fr/doc/Default.htm (in French, Google-translate it :)) Anyone knows how to install a web certificate on Android?

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• API numbers don't match on compiled PHP extension

  - by tixrus

  I'm trying to get GD into my PHP. I recently installed PHP5.3.0 on my system running Mac Leopard using mac ports. It did not come with the gd module. So I downloaded gd, compiled it as an extension module as per http://www.kenior.ch/macintosh/adding-gd-library-for-mac-os-x-leopard, made php.ini point to it, restarted apache etc. But no GD. So in apache error log it says PHP Warning: PHP Startup: gd: Unable to initialize module\nModule compiled with module API=20060613\nPHP compiled with module API=20090115\nThese options need to match\n in Unknown on line 0 So a bit of googling says I should not use the phpize I have before configuring and making these. I should use a new one called phpize5. I surely don't have any such thing. Unless its packed up inside something else in my php5.3. distro. Where do you get it. In Ubuntu I could just run sudo apt-get install php-dev, (apparently) and it would just appear by magic. At least that's what the webpage said. Unfortunately I am running MacOSX version Leopard. How can I build this GD module on Leopard so that it will match the API number in my PHP?

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• kickstart: reference floppy drive via %ksappend or %include

  - by virtualeyes

  Having trouble getting %ksappend or %include to work when referencing a local floppy drive. Booting off remote server's cd-rom drive I am able to load the CentOS 6 minimal install image, and then add ks=hd:fd0/ks-jvm.cfg to boot params to load kickstart init file from floppy disk. That works fine. The problem is that I want to load a streamlined generic init file off the floppy and then, within the init, %ksappend or %include specific config files relative to the type of server I'm building (JVM, MySQL, Apache, etc.) I do not have DHCP, networking needs to be specified statically, so %ksappend and %include both fail when attempting to reference http://some-LAN-IP/foo.cfg since networking has not yet been set. The kickstart setup only works when I glob in the entire config into a single file, which is great, but ugly and difficult to maintain when I return later, having forgotten the original setup. At this point I'd be happy if I could get %ksappend or %include working with a floppy drive reference in the %post section; that would consolidate a lot of common boilerplate that all kickstarts will rely on (sshd_config, rsync config, resolve.conf, and so on) Thanks for providing the magic floppy drive reference that is eluding me!

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• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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• solr php extension fails to run on newest Debian Wheezy

  - by hijarian

  I'm trying to use the Solr PHP extension on the recently-upgraded Debian Wheezy. It installs both from PECL and from sources flawlessly but instead of giving me expected functionality it gives me this on every PHP run: PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20100525/solr.so' - /usr/lib/php5/20100525/solr.so: undefined symbol: curl_easy_getinfo in Unknown on line 0 Also scripts which use the extension throws an error PHP Error[2]: include(SolrClient.php): failed to open stream: No such file or directory in file <...path to my autoloader...> My main point is that it was set up before and worked like a charm. In the upgrade among the relevant packages only the versions of PHP and libcurl was changed. Instance of Solr itself was left as is. I have all possible libcurl libraries: $ locate libcurl ... /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.3 /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4 /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.2.0 /usr/lib/x86_64-linux-gnu/libcurl.a /usr/lib/x86_64-linux-gnu/libcurl.la /usr/lib/x86_64-linux-gnu/libcurl.so /usr/lib/x86_64-linux-gnu/libcurl.so.3 /usr/lib/x86_64-linux-gnu/libcurl.so.4 /usr/lib/x86_64-linux-gnu/libcurl.so.4.2.0 ... /usr/lib32/libcurl.so.3 /usr/lib32/libcurl.so.4 /usr/lib32/libcurl.so.4.2.0 ... I have instaled the php5-curl package version 5.4.4-2 with aptitude. I installed the Sorl extensions both with sudo pecl install solr (with various combinations of -f and -n flags and tried solr-beta too) and with wget ... cd ... phpize ./configure make make install I'm installing the 1.0.2 version of extension because it worked before the upgrade from Squeeze to Wheezy. As I said earlier, extension installs without any errors. I have already added the extension=solr.so incantation to the /etc/php5/mods-available/solr.ini What magic should I do to make solr extension work? Is this true that the only solution that I have is to downgrade the libcurl version as it was before the upgrade?

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• Resizing a LUKS encrypted volume

  - by mgorven

  I have a 500GiB ext4 filesystem on top of LUKS on top of an LVM LV. I want to resize the LV to 100GiB. I know how to resize ext4 on top of an LVM LV, but how do I deal with the LUKS volume? mgorven@moab:~% sudo lvdisplay /dev/moab/backup --- Logical volume --- LV Name /dev/moab/backup VG Name moab LV UUID nQ3z1J-Pemd-uTEB-fazN-yEux-nOxP-QQair5 LV Write Access read/write LV Status available # open 1 LV Size 500.00 GiB Current LE 128000 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 2048 Block device 252:3 mgorven@moab:~% sudo cryptsetup status backup /dev/mapper/backup is active and is in use. type: LUKS1 cipher: aes-cbc-essiv:sha256 keysize: 256 bits device: /dev/mapper/moab-backup offset: 3072 sectors size: 1048572928 sectors mode: read/write mgorven@moab:~% sudo tune2fs -l /dev/mapper/backup tune2fs 1.42 (29-Nov-2011) Filesystem volume name: backup Last mounted on: /srv/backup Filesystem UUID: 63877e0e-0549-4c73-8535-b7a81eb363ed Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean with errors Errors behavior: Continue Filesystem OS type: Linux Inode count: 32768000 Block count: 131071616 Reserved block count: 0 Free blocks: 112894078 Free inodes: 32044830 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 992 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 RAID stride: 128 RAID stripe width: 128 Flex block group size: 16 Filesystem created: Sun Mar 11 19:24:53 2012 Last mount time: Sat May 19 13:29:27 2012 Last write time: Fri Jun 1 11:07:22 2012 Mount count: 0 Maximum mount count: 100 Last checked: Fri Jun 1 11:03:50 2012 Check interval: 31104000 (12 months) Next check after: Mon May 27 11:03:50 2013 Lifetime writes: 118 GB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: 383bcbc5-fde9-4720-b98e-2d6224713ecf Journal backup: inode blocks

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• Linux error when resume from RAM

  - by TuxPotato

  The last two times that I have resumed my laptop from sleep, it has hung and given me this set of errors: [drm:atom_op_jump] *ERROR* atombios stuck in loop for more than 1sec aborting [drm:atom_execute_table_locked] *ERROR* atombios stuck executing E692 (len 460, WS 0, PS 4) @0xE6D3 hda_intel: azx_get_responce timeout, switching to single_cmd mode: last cmd=0x01170700 ata6: softreset failed (device not ready) ata4: softreset failed (device not ready) [drm:atom_op_jump] *ERROR* atombios stuck in loop for more than 1sec aborting [drm:atom_execute_table_locked] *ERROR* atombios stuck executing E692 (len 460, WS 0, PS 4) @0xE6D3 The last two messages repeat two more times. The first time this happened, Linux's Magic SysRq worked and did a soft reboot, and after that everything was fine till it went to sleep again. It wakes up and gives me this. Here are the laptop stats: Toshiba Satellite L455D-S5976 AMD Sempron SI-42 Processor 2GB DDR2 RAM HD TruBrite Display ATI Radeon Graphics (integrated) Running Ubuntu 10.10 32 bit I'm not sure about the hard drive, but its a 250GB drive with one NTFS partition, two Hidden NTFS, one Linux Swap, and one Ext4. Can someone tell me whats wrong with my laptop? NOTE: This only happens when I close the screen. My computer doesn't go to sleep with the screen open.

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• Apache 2.2, worker mpm, mod_fcgid and PHP: Can't apply process slot

  - by mopoke

  We're having an issue on an apache server where every 15 to 20 minutes it stops serving PHP requests entirely. On occasions it will return a 503 error, other times it will recover enough to serve the page but only after a delay of a minute or more. Static content is still served during that time. In the log file, there's errors reported along the lines of: [Wed Sep 28 10:45:39 2011] [warn] mod_fcgid: can't apply process slot for /xxx/ajaxfolder/ajax_features.php [Wed Sep 28 10:45:41 2011] [warn] mod_fcgid: can't apply process slot for /xxx/statics/poll/index.php [Wed Sep 28 10:45:45 2011] [warn] mod_fcgid: can't apply process slot for /xxx/index.php [Wed Sep 28 10:45:45 2011] [warn] mod_fcgid: can't apply process slot for /xxx/index.php There is RAM free and, indeed, it seems that more php processes get spawned. /server-status shows lots of threads in the "W" state as well as some FastCGI processes in "Exiting(communication error)" state. I rebuilt mod_fcgid from source as the packaged version was quite old. It's using current stable version (2.3.6) of mod_fcgid. FCGI config: FcgidBusyScanInterval 30 FcgidBusyTimeout 60 FcgidIdleScanInterval 30 FcgidIdleTimeout 45 FcgidIOTimeout 60 FcgidConnectTimeout 20 FcgidMaxProcesses 100 FcgidMaxRequestsPerProcess 500 FcgidOutputBufferSize 1048576 System info: Linux xxx.com 2.6.28-11-server #42-Ubuntu SMP Fri Apr 17 02:45:36 UTC 2009 x86_64 GNU/Linux DISTRIB_ID=Ubuntu DISTRIB_RELEASE=9.04 DISTRIB_CODENAME=jaunty DISTRIB_DESCRIPTION="Ubuntu 9.04" Apache info: Server version: Apache/2.2.11 (Ubuntu) Server built: Aug 16 2010 17:45:55 Server's Module Magic Number: 20051115:21 Server loaded: APR 1.2.12, APR-Util 1.2.12 Compiled using: APR 1.2.12, APR-Util 1.2.12 Architecture: 64-bit Server MPM: Worker threaded: yes (fixed thread count) forked: yes (variable process count) Server compiled with.... -D APACHE_MPM_DIR="server/mpm/worker" -D APR_HAS_SENDFILE -D APR_HAS_MMAP -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled) -D APR_USE_SYSVSEM_SERIALIZE -D APR_USE_PTHREAD_SERIALIZE -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT -D APR_HAS_OTHER_CHILD -D AP_HAVE_RELIABLE_PIPED_LOGS -D DYNAMIC_MODULE_LIMIT=128 -D HTTPD_ROOT="" -D SUEXEC_BIN="/usr/lib/apache2/suexec" -D DEFAULT_PIDLOG="/var/run/apache2.pid" -D DEFAULT_SCOREBOARD="logs/apache_runtime_status" -D DEFAULT_ERRORLOG="logs/error_log" -D AP_TYPES_CONFIG_FILE="/etc/apache2/mime.types" -D SERVER_CONFIG_FILE="/etc/apache2/apache2.conf" Apache modules loaded: alias.load auth_basic.load authn_file.load authz_default.load authz_groupfile.load authz_host.load authz_user.load autoindex.load cgi.load deflate.load dir.load env.load expires.load fcgid.load headers.load include.load mime.load negotiation.load rewrite.load setenvif.load ssl.load status.load suexec.load PHP info: PHP 5.2.6-3ubuntu4.6 with Suhosin-Patch 0.9.6.2 (cli) (built: Sep 16 2010 19:51:25) Copyright (c) 1997-2008 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies

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• Default route not on LAN

  - by jarmund

  I have a network that in principle looks like this: H1---\ /----Inet1 H2---->---GW1---< H3---/ \----GW2-----Inet2 H1 and H2 = Hosts that need access to internet with GW1 Inet1 = Internet link over 3G connection Inet2 = 5GHz link to Internet (not always up) GW1 = Works as a router, automatically picking the "best" connection between Inet1 and Inet2 (the latter via GW2). GW2 = 5GHz wifi router And here's the problem: H3 only needs internet access when Inet2 is up. What i was thinking of doing was a routing table that looks like this: route to GW2 via GW1 default route is via GW2 I first set the route to GW2 via GW1 without a problem. But when i try route add default gw 1.2.3.4 (1.2.3.4 being the IP of GW2), it complains "SIOCADDRT: No such device" Is the problem that the default gw i'm trying to set is not reachable directly? Is there a different approach that would allow me to achieve this? An alternative (and hypothetical) approach: Since H3 will be using a static IP, is it possible to do some magic with iptables on GW1 to forward any packets from H3 to GW3, thereby "tricking" H3 into using GW2 as its default router?

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• Workstations cannot see new MS Server 2008 domain, but can access DHCP.

  - by Radix

  The XP Pro workstations do not see the new replacement domain upon boot; they only see their cached entry for the old (server 2003) domain controller. The old_server is not connected to the network. I have DHCP working with the same scope as the old_server. In my "before-asking" search for a solution I came across the following two articles, and I recall doing things as suggested by the articles. http://www.windowsreference.com/windows-server-2008/how-to-setup-dhcp-server-in-windows-server-2008-step-by-step-guide/ http://www.windowsreference.com/windows-server-2008/step-by-step-guide-for-windows-server-2008-domain-controller-and-dns-server-setup/ The only possible issue is: I was under the impression that the domain netbios needed to match the DC's netbios. The DC netbios is city01 while the domain's FQDN is city.domain.org (I think this is mistaken and should have been just domain.org) But, the second link led me to a post which I believe answers my question. I did as they instructed by opening Local Area Connection Properties, then selecting TCP/IPv4 and setting the sole preferred DNS server to the local hosts static IP (10.10.1.1). Search for "Your problems should clear up" for the post I'm referencing: http://forums.techarena.in/active-directory/1032797.htm Have I misunderstood their instructions? I am hoping to reach the point where I can define users and user groups. Also, does TechNet have a single theoretical overview document I could read. I really don't like treating comps as magic. I will be watching this closely and will quickly answer any questions. If I've left anything out it is because I did not know it was needed. PS: I am loath to ask obviously basic questions, but I am tired and wish to fix this before tomorrow. Also, this is my first server installation, thank you for your help.

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• Good PC-based video conference control tools?

  - by Jeremy Wadhams

  I'm looking to improve the user experience in our video conference rooms, by simplifying the things users do all the time (setting up a call, muting and unmuting, panning and zooming between a few room-appropriate presets) and totally taking away the functions that we don't use or that are more likely to ruin the experience (changing the brightness of the TV, using the VNC presenter mode). The rooms each have Tandberg Edge or MXP video units, I'm not looking at PC-based solutions like Skype or iChat. The classic way to do this would be to plunk down huge money for an AMX or Crestron panel. This does have some advantages, and I am considering that approach, but in my initial investigation, that looks expensive, inflexible, and proprietary. On the other hand, the Tandberg video units I'm looking to control are very thorough XML API (PDF), so some of the integration magic that Crestron and AMX consider to be a value add, I could reproduce at mashup speeds. Anyone aware of an Open Source or Commercial product that takes advantage of the readily available web APIs, some simple touch screen PCs, and builds a product that is more like skinning an AJAX web app, and ideally more cost effective than the proprietary panels?

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• SOLVED Install MythTV & 11.10 on Lenovo S12 (Intel atom) with wireless

  - by keepitsimpleengineer

  This is how I installed Ubuntu 11.10 and MythTV client on my Lenovo S12 (Intel Atom) laptop and use it using WiFi (see additional notes at end). I did this because the upgrade from 11.04 bricked the laptop. Note that the partitions on the Lenovo standard disk were already in place for this installation. Also note that my LAN is setup for fixed IP addresses. Downloaded and burned 11.10 x86 Desktop Ubuntu CD Connected the power supply cord, LAN wire and the external DVD USB drive. Ran Windows XP and made sure performance level "Performance" was set and "Wireless" was enabled. Booted S12 from CD Disabled Networking from icon on upper left panel icon Edited Connections… "Wired connection 1" ? Set IP address, accepted default netmask and set gateway. Also set DNS server. Good idea to check "Connection Information" here to verify everything's O.K. Selected Install Ubuntu from the initial "Install" window Verified the three items were checked (required disk space available, plugged into a power source, & connected to the Internet) Selected Download updates while installing and third party software. Hit Continue… At wireless selected don't want to connect…WiFi…now. Continue… At Installation type, selected Something else. Continue… At partition tale, selected the ext4 Linux partition, set the mount point as "/", and marked for formatting. Here I selected the main disk (/sda) for installing the boot manager. Continue… Selected or verified my Time zone. Continue… Selected my keyboard layout. Continue… Filled in the who are you fields. Make sure password is required to sign in is checked. Continue… Chose a picture. Continue… I selected import no accounts. Continue… Wait as the Install creeps along. If your screen goes blank, tap the space bar ? apparently the screen saver/power plan does this. There are several progress bars. The longest was "Installing system", and it was the next to the last one. Installation Complete window appears, Restart Now… Wait as it stops, The screen blanks then the message "…remove…media…close tray…press enter" I just unplugged the USB DVD and hit enter… It was disheartening but the screen turned Ubuntu Purple-beige and nothing happened, so I help down the power key until it shut down, the pressed it again and the Grub Boot screen appeared. Select Ubuntu… 25.The screen went blank with the little flashing underscore cursor on it and the disk light would occasionally flash. I hit the enter key and eventuality Ubuntu started. After a somewhat long time the unity desktop appeared. 11.10, unlike earlier versions, retains the connection information. Check this by checking the network icon on the upper left applet panel. Here the touch-pad·mouse quit working and I had to reboot. It takes and extremely long time to boot, sometimes requiring several power off/ power on (cold boot). You can try to get the default network manager to work, but it might not, it didn't on mine for WiFi. Thanks to: Chris at URL here's what to do… disconnect your wired Internet connection. input your wireless information into network manager open a terminal (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "terminal". Might be a good idea to drag and drop the terminal icon to the terminal, it's easy to get rid of later. click to open a terminal, and type in: sudo rmmod acer_wmi && echo "blacklist acer_wmi" >> /etc/modprobe.d/blacklist.conf and hit enter. type in your password as asked. if you have correctly entered your WiFi information and you are near your AP, you should connect immediately if not, see the URL above ? you might need to replace "network manager" with "wicd" ? I did with 11.04. Update the new 11.10, in the upper left panel applet weird·gear icon is menu with a line about updating. It's the new way to invoke Update Manager. Your lenovo S12 (intel atom) should now run the new unity Ubuntu. Point your elbow at the ceiling and pat yourself on the back. Installing Mythbuntu Client 24.1 Open mythbuntu.org/repos (I urge you not to directly use Ubuntu Software Center for this) Install Mythbuntu Repos Save the file (in ~/Downloads, the default) Run the file ? it will update your repositories so that you will get the proper installation sources ? it will start Ubuntu Software Center to do this ? Click Install… You will need your password. Debconf window will open, select by making sure check mark is in the little box "Would you like to activate…". Forward… Which version? At the time of writing the current "Stable" version was 24.1, select 0.24.x… Forward… Read the message, then forward… Delete the downloaded file. Install synaptic (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "synaptic". Click on the synaptic icon. Ubuntu Software Center will open and allow you to install synaptic package manager. Open Synaptic (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "Synaptic". Might be a good idea to drag and drop the terminal icon to the terminal, it's easy to get rid of later. Run synaptic, read the intro, and close the intro window. Type in mythbuntu-control-centre in the Quick filter text box, and then select it "Mark for installation" by clicking on the box next to it's name. Marvel at the additional to be installed items, then select "?Mark"… At the top of the synaptic window click on the "? Apply" button. Marvel at the amount of stuff to be installed, the click on "Apply". When finished, close finished window and synaptic. Open mythbuntu-control-centre (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "mythbuntu". Might be a good idea to drag and drop the mythbuntu-control-centre icon to the terminal, it's easy to get rid of later. You can now configure and install the frontend. Go down the icon totem on the right side of the window and click as needed… System roles. ? No Backend, Desktop Frontend, and Ubuntu Desktop. Apply… & Apply changes… & Password… MySQL Configuration ? from backend ? Setup General Alt-N(ext) Alt-N(ext) Stetting Access Setup PIN code: ~~~~ Input Security key and click "Test Connection", if ?, then Apply… & Apply… {note: for some inexplicable reason, control centre hung on this, but when I restarted it, it was set properly} Graphics drivers, When I did this, only the Broadcom wireless driver showed up. I closed without doing anything. Services. I enabled SSH & Samba. Apply… & Apply… Repositories. Asked & Answered. MythExport. Pass, I believe it requires backend on the same system. Proprietary Codec Support. Check to enable, Apply… & Apply… System Updates. No action necessary, will be a part of the Ubuntu update mechanism. Themes and Artwork. For themes, I selected Enable/Update all. Apply… & Apply… Infrared & Startup behavior and Plugins. Defer until you know more. Close software centre. Open mythTV (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "mythTV". Might be a good idea to drag and drop the mythTV icon to the terminal, it's easy to get rid of later. Incorrect Group Membership. Fix this by clicking "Yes"… Log out/end. Do this by clicking "Yes"… For my Lenovo S12, I had to manually restart Ubuntu - and still with the very long restart…/no start/cold boot/reboot/pressing the shift key required Open mythTV (unity dash, top of icon totem, open, and make sure the ruler&pen icon on the bottom is selected, 2nd from left) type in "mythTV". Might be a good idea to drag and drop the mythTV icon to the terminal, it's easy to get rid of later. Will open with Select country & language. Do so. then get message with "No", hit "Ok" and arrive at the data base Configuration 1/2 screen. You will need your brackend password, from backend ? Setup General Database Configuration 1/2 Password:~? Enter this Hit Alt-n to go to the next page. Select "Use custom id…", then enter a custom ID, I use the machine's name. Hit finish, and MythTV should start up with all default settings. For the lenovo S12, the first thing you want to do is to set Playback profiles to "Normal". From Setup TV Settings Playback Alt-N(ext) Alt-N(ext) Playback Profiles (3/8) : Change Current Video Playback Profile to "Normal". You can fiddle with this setting later. For the lenovo S12, the second thing is to get the sound going. From Setup General Alt-N(ext) Alt-N(ext) Alt-N(ext) Audio System: The top of the screen is a button title "Scan for audio devices", move the highlight there and press the Space bar. Then Tab down to Audio Output Device: and left-right arrow until "ALSA:hw:Card=Intel,DEV=0" is selected. Then Alt-N(ext) until "Finish". Now you should have sound. You should now have MythTV working nicely on the Lenovo S12 Notes about wireless: Running Lenovo S12 on wireless is demanding on both power and WiFi connection. Best results will be obtained when running on power and wired connection. I run my S12 on wireless, actually two serial connections with two access points, something that is not easy to achieve. Here Mythbuntu client-server (in den) <? wireless link 1 <?office LAN? wireless link 2 <? Lenovo S12 Ubuntu 11.10 The office LAN is fixed IP behind an Untangle firewall router. There is another MythTV client on Ubuntu 10.10 computer in the office (which has always worked well). ProblemMythbuntu\Win7 client hangs with frozen frames, short segment of audio repeating. Hardware Rosewill RNX-G300EX IEEE 802.11b/g PCI Wireless Card on client-server 2 Linksys WRT54GL wireless broadband routers on LAN for link1 and link 2 WRT54GL FirmwareDD-WRT v24-sp2(07/22/09) voip set up to act as an access point. Note? many people advised this was an unworkable scheme, and in probably most cases it will be. Solution? Set up DD-WRT with the following Wireless settings… Basic Channel: Different fixed channels at least 4 difference, I use 6 & 11 Basic Sensitivity Range (ACK timing): 50 MAC filter use filter: Enable, Selected Permit only clients listed to access… Requires adding MAC addresses in "Edit MAC Filter List" This causes the 54GL's to ignore any but the listed MAC address, down side, no "guest" capability. Advanced Basic rate: All Advanced CTS Protection Mode: Off Advanced Frame Burst: Enable Advanced Max associate clients: 4 for client link 2, 1 for client-server link 1 Advanced AP isolation: Enable Advanced Preamble: Short Advanced Afterburner: On Advanced Wireless GUI access: Off Advanced WMM support: Off Other settings: default for supplied firmware. Why I suspect this worked? The 54GL Access Points's with the firmware's setting are set to handle a multiple client, wide area situation. With these mods I reconfigured them for a small area, few client situation, disabling Advanced WMM probably the most important. In addition, the client mythtv when used all other users of its access point are turned off except for a Skype phone. Also, the client-server is set up to allow other connections though it's LAN connection, and these are used to connect the TV and disc players, not used when client is being used.

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• suggestions for firewall/router project using *BSD or Linux

  - by Adeodatus

  Hi All, I have a project in mind and I'd love to hear some ideas on some open source solutions with COTS hardware. I have a few 24 and/or 48 port managed layer2 switches with customers potentially on each port (though its usually about 20-30). Right now the switch has a bridged network and backhaul the traffic to our core to a centralized DHCP server. I need to move them to a NAT solution and, while doing this, I'd like to protect the customers on each port from the customer traffic on the other ports. I also need to be able to port forward from the public side of the firewall/nat box to specific hardware on the inside of the nat machine (easy enough, I know). My first thoughts are to build an appliance-like box (the fewer moving parts the better) that can do filtering and NAT with rfc1918 an address range being handed out via a DHCP server on the appliance. A caching DNS server on the appliance would be a plus since we backhaul everything to the core. I'd like to run FreeBSD but I'm open. Now, to try to limit the broadcast traffic thats visible I was thinking of doing each port on the switch as a different vlan and have the switch do trunking to the private NIC on the FreeBSD/appliance. I'd probably need to do some magic on the freebsd NIC to get this working but it should. We have the parts to build these systems. So, does this make sense? Are there any other solutions out there that we don't have to spend money on but can use our parts to create something? Are there any good distros that could do this already (monowall)?? I may or may not admin this solution so a secure web configuration and management tool would be a plus in the other admins' minds. Thoughts?

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• Failed to start apache Can't open /etc/apache2/envvars

  - by bumperbox

  i have had this problem a couple of times now and i am not sure what is causing it Failed to start apache : .: 45: Can't open /etc/apache2/envvars when i look at a dir listing, i get these question marks next to envvars, does anyone know what that means? os is ubuntu 10 if that helps drwxr-xr-x 7 root root 4096 Jan 29 11:56 . drwxr-xr-x 83 root root 4096 Feb 4 10:34 .. -rw-r--r-- 1 root root 8113 Sep 29 01:52 apache2.conf -rw-r--r-- 1 root root 8027 Oct 3 22:26 apache2.conf.dpkg-old drwxr-xr-x 2 root root 4096 Jan 29 11:56 conf.d ?????????? ? ? ? ? ? envvars -rw-r--r-- 1 root root 0 Oct 3 22:25 httpd.conf ?????????? ? ? ? ? ? magic drwxr-xr-x 2 root root 4096 Jan 29 11:56 mods-available drwxr-xr-x 2 root root 4096 Jan 29 10:18 mods-enabled ?????????? ? ? ? ? ? ports.conf drwxr-xr-x 2 root root 4096 Jan 29 11:56 sites-available drwxr-xr-x 2 root root 4096 Jan 29 11:55 sites-enabled UPDATE Just heard back from the hosting company, they move my VPS to a new hardware node last night, and something at their end wasn't quite right which caused the issue

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• Mac OS X Client With Static DHCP Assignment Requests Wrong IP via Option 50

  - by Starchy

  I have a number of Mac (and a few Linux) laptops getting DHCP from a Force10 layer 3 switch, the only DHCP server on the subnet. There's a global dynamic pool, and for each full-time employee's laptop I have a single IP static pool set by MAC address. One and only one of the clients, running OS X 10.7.5, consistently fails to get a static assignment. The MAC address in the static pool definition has been carefully re-checked. Running tcpdump on a mirrored port when the laptop connects, I see that it is specifically requesting 10.100.0.252 (a dynamic address): 11:32:10.108280 IP (tos 0x0, ttl 255, id 28293, offset 0, flags [none], proto UDP (17), length 328) 0.0.0.0.bootpc > broadcasthost.bootps: [udp sum ok] BOOTP/DHCP, Request from 3c:07:54:xx:xx:xx (oui Unknown), length 300, xid 0x1399da89, Flags [none] (0x0000) Client-Ethernet-Address 3c:07:54:xx:xx:xx (oui Unknown) Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: Request Parameter-Request Option 55, length 9: Subnet-Mask, Default-Gateway, Domain-Name-Server, Domain-Name Option 119, LDAP, Option 252, Netbios-Name-Server Netbios-Node MSZ Option 57, length 2: 1500 Client-ID Option 61, length 7: ether 3c:07:54:xx:xx:xx Requested-IP Option 50, length 4: 10.100.0.252 Lease-Time Option 51, length 4: 7776000 Hostname Option 12, length 10: "host-name" END Option 255, length 0 PAD Option 0, length 0, occurs 8 I haven't been able to find any extra system prefs or unusual software on the laptop. Disabling the interface and rebooting or temporarily setting the IP manually both fail to make any difference. Any suggestions appreciated.

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• Windows XP Installation problems

  - by Samurai Waffle

  I'm having trouble installing Windows XP on a computer... My friend gave me her old computer, it was riddled with viruses and ran extremely slow. I did my best to clean it out, and after a bit I discovered it had a boot sector virus. So I downloaded the Ultimate Boot CD (installed it on a flash drive), and ran Darik's nuke and boot to completely wipe the hard drive. I then tried to reinstall Windows XP from a USB drive... It doesn't work. The computer just stalls and never boots. The computers dvd drive doesn't work, so I borrowed a spare drive that another friend had, and tried to run a Windows XP cd. For a bit I got the stop 7B error, but now it just stalls like the USB drive does. Since then I've booted back into the Ultimate Boot CD, and ran partition magic. Repartitioned the Hard Drive, and copied the files on the Windows cd to the hard drive. I was wondering if there is any way I can make it run the setup.exe off the hard drive. I have the UBCD at my disposal, but have yet to come up with a way to do it. Any help is greatly appreciated.

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• Convert mp4 video to a format xbox 360 can play

  - by Björn Lindqvist

  Here is a video file my Xbox 360 refuses to play: $ MP4Box -info video.mp4 * Movie Info * Timescale 90000 - Duration 02:18:33.365 Fragmented File no - 2 track(s) File Brand mp42 - version 0 Created: GMT Sat Jul 21 07:08:55 2012 File has root IOD (9 bytes) Scene PL 0xff - Graphics PL 0xff - OD PL 0xff Visual PL: ISO Reserved Profile (0x7f) Audio PL: High Quality Audio Profile @ Level 2 (0x0f) No streams included in root OD iTunes Info: Encoder Software: HandBrake 0.9.6 2012022800 Track # 1 Info - TrackID 1 - TimeScale 90000 - Duration 02:18:33.235 Media Info: Language "Undetermined" - Type "vide:avc1" - 199318 samples Visual Track layout: x=0 y=0 width=1280 height=688 MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21 AVC/H264 Video - Visual Size 1280 x 688 AVC Info: 1 SPS - 1 PPS - Profile High @ Level 4.1 NAL Unit length bits: 32 Self-synchronized Track # 2 Info - TrackID 2 - TimeScale 48000 - Duration 02:18:33.365 Media Info: Language "English" - Type "soun:mp4a" - 389689 samples MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40 MPEG-4 Audio MPEG-4 Audio AAC LC - 6 Channel(s) - SampleRate 48000 Synchronized on stream 1 $ avconv -i video.mp4 avconv version 0.8.4-4:0.8.4-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers built on Nov 6 2012 16:51:33 with gcc 4.6.3 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4': Metadata: major_brand : mp42 minor_version : 0 compatible_brands: mp42isomavc1 creation_time : 2012-07-21 07:08:55 encoder : HandBrake 0.9.6 2012022800 Duration: 02:18:33.36, start: 0.000000, bitrate: 2299 kb/s Stream #0.0(und): Video: h264 (High), yuv420p, 1280x688, 1973 kb/s, 23.98 fps, 90k tbr, 90k tbn, 180k tbc Metadata: creation_time : 2012-07-21 07:08:55 Stream #0.1(eng): Audio: aac, 48000 Hz, 5.1, s16, 319 kb/s Metadata: creation_time : 2012-07-21 07:08:55 At least one output file must be specified What tool, such as ffmpeg or mencoder, and what magic command line incantation should I use to transcode this file into a format Xbox 360 can play? I want the transcode process to retain as good video quality as possible.

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