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  • Correct Path for Git Remote Add from Amazon EC2 Instance to OSX Client Machine

    - by filmnut
    I'm trying to do a git remote add from a repository that sits on a remote Amazon AMI back to a cloned copy of the SAME repository that is sitting on my local OSX machine. I'm confused about what file path to use. I assume it's something like: git remote add my_clone <OSX_User_Name>@<OSX_HOST_NAME>:<PATH_TO_CLONED_REPO> I obviously know what my <OSX_User_Name> is, and I can figure out my <PATH_TO_CLONED_REPO>, but I have no idea how to determine a <OSX_HOST_NAME> that would actually work. Can I just put in my external IP address, followed by my machine's internal IP address? (Note that I'm working behind a router.) Is ssh:// the correct protocol? Do I need to set up ssh access from the Amazon EC2 machine to the local OSX machine?

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  • Drupal install on remote mysql

    - by user1448660
    I am trying to install drupal on remote mysql server. I have created the user in mysql and granted the the privileges. I am able to connect through command line from my web server like this "mysql -u xxxx -h 10.xxx.yy.zz3 -p". But when I tried to install drupal I get "SQLSTATE[28000] [1045] Access denied for user 'xxxx'@'localhost'". I have given the privileges for "xxxx"@"10.xxx.yy.zz3" but drupal appends localhost instead of IP to user name. I have changed settings.php to mysql server IP. What am I missing?

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  • Opening up TCP Sockets in j2ee Webapplication

    - by Gvenez
    Hello, We have to communicate with a C++ component from a J2ee web application and my proposal involved using JMS server to communicate with the C++ component which is located on other machine. However the developer of the C++ component wants me to open up TCP/IP sockets from the webapplication and communicate over XML. My view is that socket programming in web application is error prone and will not scale well since there is a limited amount of sockets that can be opened up. Please let me have your architecture/design preference on using JMS vs TCP/IP sockets. Thank you

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  • How to perform DNS query on iOS

    - by yasirmturk
    i want to perform some DNS queries e.g. to get IP records against a specific domain name, i am looking for a preferred way or some useful snippet for this on iOS 3.2+ SDK. thanx in advance part from other snippets i found this code Boolean result; CFHostRef hostRef; NSArray *addresses; NSString *hostname = @"apple.com"; hostRef = CFHostCreateWithName(kCFAllocatorDefault, (CFStringRef)hostname); if (hostRef) { result = CFHostStartInfoResolution(hostRef, kCFHostAddresses, NULL); // pass an error instead of NULL here to find out why it failed if (result == TRUE) { addresses = (NSArray*)CFHostGetAddressing(hostRef, &result); } } if (result == TRUE) { [addresses enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { NSString *strDNS = [NSString stringWithUTF8String:inet_ntoa(*((struct in_addr *)obj))]; NSLog(@"Resolved %d->%@", idx, strDNS); }]; } else { NSLog(@"Not resolved"); } but this is producing same IP for every host Resolved 0-220.120.64.1 any help??

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  • Delphi and mysql - Unable to connent to server..maybe custom connection reqd

    - by Steve
    I am coding an application for my company wherein i want to parse the results of a mysql query and display them in my application but i am facing a problem conecting to the database. the ip address of the server is : 172.30.192.20 and before i can ping it i have to add route on my pc something like this route add 172.30.192.0 mask 255.255.255.0 172.30.192.56 where 172.30.192.56 is the gateway Now whenever i try to connect 172.30.192.20 which is where the sql server is running my appplication instead connects to 172.30.192.56 i am coding the application in delphi and have used TmySQL After this didnt workout i tried an application called SQLwave. I just entered the server ip address and was able to connect to the database without any problems. it seems sqlwave uses mydac which is why even i tried using it but using the default connection options and setting i was still not able to connect. it seems sqlwave uses a custom connection using mydac i just want to know whats going wrong with my connection

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  • Perl - Choose interface to connect through

    - by Dieterve
    I have 2 interfaces on my server, eth0 and eth0:0. Those are 2 different external ips and obviously 2 different reverse domains. When i open a IO::Socket::INET Perl uses the eth0 interface by default. I would like to use the second interface (eth0:0) because this has a different ip and i dont want to use my main ip/domain. I have absolutely no idea how to select which interface to connect through. Code i use to open a socket: my $sock = new IO::Socket::INET(PeerAddr => $server, PeerPort => $serverPort, Proto => 'tcp') or die "Can't connect to server: $!";

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  • Firewall configuration. (Windows server 2008)

    - by Jon
    Hello. I'm having a little problem with configuring the firewall on my server. I only want a specific range of IPs to be able to access specific ports. For example, I'm having alot of password attempts to some of my servers, so I want to make it more safe by only allowing incoming connections from a specific range of domain. Example: My IP is usually adsl-324-4.somecompany.com so I want to allow *.somecpompany.com to connect, as my IP is dynamic. That would get rid of alot of attempts to hack into my servers. But I have no idea how to mask a domain like that for the firewall. How could I for example allow all incoming connections from *.is? Thanks.

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  • Godaddy registrar and Amazon Web Services EC2/Route 53

    - by soshannad
    Ok - I currently have a site hosted on Godaddy and they are the registrar for my domain. My goal is to have my site hosted on AWS with an EC2 server, which I have already set up and it is ready to go. In order to migrate my domain name to Amazon I have set up an A record with Godaddy and another A record with Route 53 (Amazon's routing service) with both of them pointing to the new static IP of the AWS site. My question is - Godaddy told me that I should leave my nameservers as Godaddy since my email is with them and set up an MX record wit Amazon pointing to it. Does this sound correct? Can you leave nameservers with Godaddy and have A records pointed to the new IP? Are there any benefits/cons to this? *FOR THE RECORD - My site is DOWN right now after doing the change - Godaddy says it will take 2 hours to come back, but I'm not sure if their nameserver recommendation is correct.

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  • Anyone saw a worst written function than this? [closed]

    - by fvoncina
    string sUrl = "http://www.ipinfodb.com/ip_query.php?ip=" + ip + "&output=xml"; StringBuilder oBuilder = new StringBuilder(); StringWriter oStringWriter = new StringWriter(oBuilder); XmlTextReader oXmlReader = new XmlTextReader(sUrl); XmlTextWriter oXmlWriter = new XmlTextWriter(oStringWriter); while (oXmlReader.Read()) { oXmlWriter.WriteNode(oXmlReader, true); } oXmlReader.Close(); oXmlWriter.Close(); // richTextBox1.Text = oBuilder.ToString(); XmlDocument doc = new XmlDocument(); doc.LoadXml(oBuilder.ToString()); doc.Save(System.Web.HttpContext.Current.Server.MapPath(".") + "data.xml"); DataSet ds = new DataSet(); ds.ReadXml(System.Web.HttpContext.Current.Server.MapPath(".") + "data.xml"); string strcountry = "India"; if (ds.Tables[0].Rows.Count > 0) { strcountry = ds.Tables[0].Rows[0]["CountryName"].ToString(); }

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  • PHP - trying to automate/loop a save function

    - by Homer_J
    EDIT: the difference between the pages are the simply $q1, $q2, $q3 becomes, for example, $q13, $q14, $q15 - they are questions in the form. Hi all, I have the following code: $rguid = $_POST["r"]; $ip=substr($_SERVER['REMOTE_ADDR'], 0, 50); $browser=substr($_SERVER['HTTP_USER_AGENT'], 0, 255); $q1 = $_POST["q1"]; $q2 = $_POST["q2"]; $q3 = $_POST["q3"]; $q4 = $_POST["q4"]; $q5 = $_POST["q5"]; $q6 = $_POST["q6"]; $q7 = $_POST["q7"]; $q8 = $_POST["q8"]; $respondent_id = decode_respondent_guid($rguid); $rcount=respondent_status($respondent_id); if ($rcount==0) { $proc = mysqli_prepare($link, "INSERT INTO tresults (respondent_id, ip, browser, q1, q2, q3, q4, q5, q6, q7, q8) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);"); mysqli_stmt_bind_param($proc, "issiiiiiiii", $respondent_id, $ip, $browser, $q1, $q2, $q3, $q4, $q5, $q6, $q7, $q8); mysqli_stmt_execute($proc); $mysql_error = mysqli_error($link); if ($mysql_error!="") { printf("Unexpected database error: %s\n", $mysql_error); mysqli_stmt_close($proc); mysqli_clean_connection($link); exit(); } else { mysqli_stmt_close($proc); mysqli_clean_connection($link); update_completion_status($respondent_id, 'Started'); header("Location: page2.php?r=".$rguid); } } This code works a treat - no problem. At the moment, that code appears on a 'save' page that relates to a 'form' page (i.e. if I have 5 .php pages with a form on each, I need 5 save.php pages to save each pages data to the database) to save data to my SQL database. What I would like is to have a single save.php page that will work with as many 'form' pages as I have. So instead of manually having to setup and change each save page, it automates it. I've no idea of the coding to do this, though I suspect something like a foreacg or loop etc. Any suggestions? Thanks, Homer.

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  • What information about a user is available via PHP?

    - by Camran
    This is about a classifieds website, where anyone may post classifieds. I have a security database which I intend to fill with information about the user who posts the classifieds. I intend to record information such as IP, name, tel, email, classified_text, classified_title etc etc. The reason for all this is that sometimes people become victims of fraud (fake classifieds etc). So I wonder, what information is possible to get from the poster which may help in tracking him/her down? IP is a given, but what else could be useful? And I would much like examples of how it would be useful also, as well as the code for it please, like $_SERVER['REMOTE_ADDR']. And btw, I use PHP and have Sql as a database. Thanks

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  • PHP Localhost Application connect to server database

    - by Cross Vander
    I want to ask about how to connect my localhost application (C:xampp/htdocs/myproject) to database at my server host (www.someweb.somedomain)? Am I possible to do that? If it is, how to connect it at my php config? Right now my config (server.php) is: <?php $host = "my web IP public:3306"; $user = "root"; $pass = ""; $db = "dispatcherDB"; $conn = mysql_connect($host, $user, $pass) or die ("Cant connect to mySQL"); mysql_select_db($db); ?> what I got: Warning: mysql_connect(): No connection could be made because the target machine actively refused it. in C:\xampp\htdocs\XMS\server.php on line 7 So, what must I filled for $host? I'm trying using website IP, it still can't connect. Maybe there's someone here have experience at this problem? Sorry for my bad English

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  • I am requesting ideas on manipulating output from an array and parse to something useful

    - by Cyber Demon
    First I am new to PS scripting. Please be gentle. This simple script I have written is ok. $Iplist = Get-Content ips.txt foreach ($ip in $Iplist) { .\psping -h -n 3 -w 0 $ip >> results.csv } Move-Item "C:\ping\results.csv" ("C:\ping\aftermath\{0:yyyyMMddhhmm}.csv" -f (get-date)) The Output is as follows, as an example (I used www.google.com): Pinging 74.125.225.48 with 32 bytes of data: 3 iterations (warmup 0) ping test: Reply from 74.125.225.48: 54.14ms Reply from 74.125.225.48: 54.85ms Reply from 74.125.225.48: 54.48ms Ping statistics for 74.125.225.48: Sent = 3, Received = 3, Lost = 0 (0% loss), Minimum = 54.14ms, Maximum = 54.85ms, Average = 54.49ms Latency Count 54.14 1 54.17 0 54.21 0 54.25 0 54.29 0 54.32 0 54.36 0 54.4 0 54.44 0 54.47 1 54.51 0 54.55 0 54.59 0 54.62 0 54.66 0 54.7 0 54.74 0 54.77 0 54.81 0 54.85 1 What I'm looking for is something to show me the following as an output. ServerIP Name TimeStamp Results AverageResponseTime in milli-seconds www.google.com 2014-08-14T16:09:59 Up 53 Can you guide me?

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  • Calculating number of online visitors?

    - by Syom
    i need to show the number of online visitors, but there is a problem with selecting algoritm to do it! maybe i must create a table in DB, where i'll store ip addresses of visitors and time of visit! by so i can show the count of ip addresses, which's time = NOW() - 10 minutes, for example...("now()-10 minutes" is just to show the logic, i know that this is not a function:) is this goog way to go? or maybe it's better to use AJAX methods to store the data? please give me an idea. Thanks

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  • Respond to a UDP message

    - by JDCAce
    I have a pair of very simple C# programs (server and client). The client's user enters an IP address, and the client sends a UDP message to the server. The server uses UDPClient.Receive() to listen to IPAddress.Any, prints out the message it received and where it was sent from (the client's IP address), then sends a UDP message back to the client. The problem is in that last part: my client is not receiving any message. It listens only to the server, instead of IPAddress.Any. The SendUdpMessage() and WaitForMessage() methods are identical, except for the IPAddress.Any part. I cannot find what's wrong! I can post the code if I need to, but I don't know which part is relevant, and I don't want to post the entire program (about 150 lines combined).

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  • Upgrading Team Foundation Server 2008 to 2010

    - by Martin Hinshelwood
    I am sure you will have seen my posts on upgrading our internal Team Foundation Server from TFS2008 to TFS2010 Beta 2, RC and RTM, but what about a fresh upgrade of TFS2008 to TFS2010 using the RTM version of TFS. One of our clients is taking the plunge with TFS2010, so I have the job of doing the upgrade. It is sometimes very useful to have a team member that starts work when most of the Sydney workers are heading home as I can do the upgrade without impacting them. The down side is that if you have any blockers then you can be pretty sure that everyone that can deal with your problem is asleep I am starting with an existing blank installation of TFS 2010, but Adam Cogan let slip that he was the one that did the install so I thought it prudent to make sure that it was OK. Verifying Team Foundation Server 2010 We need to check that TFS 2010 has been installed correctly. First, check the Admin console and have a root about for any errors. Figure: Even the SQL Setup looks good. I don’t know how Adam did it! Backing up the Team Foundation Server 2008 Databases As we are moving from one server to another (recommended method) we will be taking a backup of our TFS2008 databases and resorting them to the SQL Server for the new TFS2010 Server. Do not just detach and reattach. This will cause problems with the version of the database. If you are running a test migration you just need to create a backup of the TFS 2008 databases, but if you are doing the live migration then you should stop IIS on the TFS 2008 server before you backup the databases. This will stop any inadvertent check-ins or changes to TFS 2008. Figure: Stop IIS before you take a backup to prevent any TFS 2008 changes being written to the database. It is good to leave a little time between taking the TFS 2008 server offline and commencing the upgrade as there is always one developer who has not finished and starts screaming. This time it was John Liu that needed 10 more minutes to make his changes and check-in, so I always give it 30 minutes and see if anyone screams. John Liu [SSW] said:   are you doing something to TFS :-O MrHinsh [SSW UK][VS ALM MVP] said:   I have stopped TFS 2008 as per my emails John Liu [SSW] said:   haven't finish check in @_@   can we have it for 10mins? :) MrHinsh [SSW UK][VS ALM MVP] said:   TFS 2008 has been started John Liu [SSW] said:   I love you! -IM conversation at TFS Upgrade +25 minutes After John confirmed that he had everything done I turned IIS off again and made a cup of tea. There were no more screams so the upgrade can continue. Figure: Backup all of the databases for TFS and include the Reporting Services, just in case.   Figure: Check that all the backups have been taken Once you have your backups, you need to copy them to your new TFS2010 server and restore them. This is a good way to proceed as if we have any problems, or just plain run out of time, then you just turn the TFS 2008 server back on and all you have lost is one upgrade day, and not 10 developer days. As per the rules, you should record the number of files and the total number of areas and iterations before the upgrade so you have something to compare to: TFS2008 File count: Type Count 1 1845 2 15770 Areas & Iterations: 139 You can use this to verify that the upgrade was successful. it should however be noted that the numbers in TFS 2010 will be bigger. This is due to some of the sorting out that TFS does during the upgrade process. Restore Team Foundation Server 2008 Databases Restoring the databases is much more time consuming than just attaching them as you need to do them one at a time. But you may be taking a backup of an operational database and need to restore all your databases to a particular point in time instead of to the latest. I am doing latest unless I encounter any problems. Figure: Restore each of the databases to either a latest or specific point in time.     Figure: Restore all of the required databases Now that all of your databases are restored you now need to upgrade them to Team Foundation Server 2010. Upgrade Team Foundation Server 2008 Databases This is probably the easiest part of the process. You need to call a fire and forget command that will go off to the database specified, find the TFS 2008 databases and upgrade them to 2010. During this process all of the 6 main TFS 2008 databases are merged into the TfsVersionControl database, upgraded and then the database is renamed to TFS_[CollectionName]. The rename is only the database and not the physical files, so it is worth going back and renaming the physical file as well. This keeps everything neat and tidy. If you plan to keep the old TFS 2008 server around, for example if you are doing a test migration first, then you will need to change the TFS GUID. This GUID is unique to each TFS instance and is preserved when you upgrade. This GUID is used by the clients and they can get a little confused if there are two servers with the same one. To kick of the upgrade you need to open a command prompt and change the path to “C:\Program Files\Microsoft Team Foundation Server 2010\Tools” and run the “import” command in  “tfsconfig”. TfsConfig import /sqlinstance:<Previous TFS Data Tier>                  /collectionName:<Collection Name>                  /confirmed Imports a TFS 2005 or 2008 data tier as a new project collection. Important: This command should only be executed after adequate backups have been performed. After you import, you will need to configure portal and reporting settings via the administration console. EXAMPLES -------- TfsConfig import /sqlinstance:tfs2008sql /collectionName:imported /confirmed TfsConfig import /sqlinstance:tfs2008sql\Instance /collectionName:imported /confirmed OPTIONS: -------- sqlinstance         The sql instance of the TFS 2005 or 2008 data tier. The TFS databases at that location will be modified directly and will no longer be usable as previous version databases.  Ensure you have back-ups. collectionName      The name of the new Team Project Collection. confirmed           Confirm that you have backed-up databases before importing. This command will automatically look for the TfsIntegration database and verify that all the other required databases exist. In this case it took around 5 minutes to complete the upgrade as the total database size was under 700MB. This was unlike the upgrade of SSW’s production database with over 17GB of data which took a few hours. At the end of the process you should get no errors and no warnings. The Upgrade operation on the ApplicationTier feature has completed. There were 0 errors and 0 warnings. As this is a new server and not a pure upgrade there should not be a problem with the GUID. If you think at any point you will be doing this more than once, for example doing a test migration, or merging many TFS 2008 instances into a single one, then you should go back and rename the physical TfsVersionControl.mdf file to the same as the new collection. This will avoid confusion later down the line. To do this, detach the new collection from the server and rename the physical files. Then reattach and change the physical file locations to match the new name. You can follow http://www.mssqltips.com/tip.asp?tip=1122 for a more detailed explanation of how to do this. Figure: Stop the collection so TFS does not take a wobbly when we detach the database. When you try to start the new collection again you will get a conflict with project names and will require to remove the Test Upgrade collection. This is fine and it just needs detached. Figure: Detaching the test upgrade from the new Team Foundation Server 2010 so we can start the new Collection again. You will now be able to start the new upgraded collection and you are ready for testing. Do you remember the stats we took off the TFS 2008 server? TFS2008 File count: Type Count 1 1845 2 15770 Areas & Iterations: 139 Well, now we need to compare them to the TFS 2010 stats, remembering that there will probably be more files under source control. TFS2010 File count: Type Count 1 19288 Areas & Iterations: 139 Lovely, the number of iterations are the same, and the number of files is bigger. Just what we were looking for. Testing the upgraded Team Foundation Server 2010 Project Collection Can we connect to the new collection and project? Figure: We can connect to the new collection and project.   Figure: make sure you can connect to The upgraded projects and that you can see all of the files. Figure: Team Web Access is there and working. Note that for Team Web Access you now use the same port and URL as for TFS 2010. So in this case as I am running on the local box you need to use http://localhost:8080/tfs which will redirect you to http://localhost:8080/tfs/web for the web access. If you need to connect with a Visual Studio 2008 client you will need to use the full path of the new collection, http://[servername]/tfs/[collectionname] and this will work with all of your collections. With Visual Studio 2005 you will only be able to connect to the Default collection and in both VS2008 and VS2005 you will need to install the forward compatibility updates. Visual Studio Team System 2005 Service Pack 1 Forward Compatibility Update for Team Foundation Server 2010 Visual Studio Team System 2008 Service Pack 1 Forward Compatibility Update for Team Foundation Server 2010 To make sure that you have everything up to date, make sure that you run SSW Diagnostics and get all green ticks. Upgrade Done! At this point you can send out a notice to everyone that the upgrade is complete and and give them the connection details. You need to remember that at this stage we have 2008 project upgraded to run under TFS 2010 but it is still running under that same process template that it was running before. You can only “enable” 2010 features in a process template you can’t upgrade. So what to do? Well, you need to create a new project and migrate things you want to keep across. Souse code is easy, you can move or Branch, but Work Items are more difficult as you can’t move them between projects. This instance is complicated more as the old project uses the Conchango/EMC Scrum for Team System template and I will need to write a script/application to get the work items across with their attachments in tact. That is my next task! Technorati Tags: TFS 2010,TFS 2008,VS ALM

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  • Using Oracle Enterprise Manager Ops Center to Update Solaris via Live Upgrade

    - by LeonShaner
    Introduction: This Oracle Enterprise Manager Ops Center blog entry provides tips for using Ops Center to update Solaris using Live Upgrade on Solaris 10 and Boot Environments on Solaris 11. Why use Live Upgrade? Live Upgrade (LU) can significantly reduce downtime associated with patching Live Upgrade avoids dropping to single-user mode for long periods of time during patching Live Upgrade relies on an Alternate Boot Environment (ABE)/(BE), which is patched while in multi-user mode; thereby allowing normal system operations to continue with the active BE, while the alternate BE is being patched Activating an newly patched (A)BE is essentially a reboot; therefore the downtime is ~= reboot Admins can easily revert to the prior Boot Environment (BE) as a safeguard / fallback. Why use Ops Center to patch via Live Upgrade, Alternate Boot Environments, and Solaris 11 equivalents? All the benefits of Ops Center's extensive patch and package knowledge base can be leveraged on top of Live Upgrade Ops Center can orchestrate patching based on Live Upgrade and Solaris 11 features, which all works together to minimize downtime Ops Centers advanced inventory and reporting features assurance that each OS is updated to a verifiable, consistent standard, rather than relying on ad-hoc (error prone) procedures and scripts Ops Center gives admins control over the boot environment specifications or they can let Ops Center decide when a BE is necessary, thereby reducing complexity and lowering the opportunity for user error Preparing to use Live Upgrade-like features in Solaris 11 Requirements and information you should know: Global Zone Root file-systems must be separate from Solaris Container / Zone filesystems Solaris 11 has features which are similar in concept to Live Upgrade on Solaris 10, but differ greatly in implementationImportant distinctions: Solaris 11 assumes ZFS root Solaris 11 adds Boot Environments (BE's) as an integrated feature (see beadm) Solaris 11 BE's avoid single-user patching (vs. Solaris 10 w/ ZFS snapshot=ABE). Solaris 11 Image Packaging System (IPS) has hooks for BE creation, as needed Solaris 11 allows pkgs to be installed + upgraded in alternate BE (e.g. instead of the live system) but it is controlled on a per-pkg basis Boot Environments are activated across a reboot; instead of spending long periods installing + upgrading packages in single user mode. Fallback to a prior BE is a function of the BE infrastructure (a la beadm). (Generally) Reboot + BE activation can be much much faster on Solaris 11 Preparing to use Live Upgrade on Solaris 10 Requirements and information you should know: Global Zone Root file-systems must be separate from Solaris Container / Zone filesystems Live Upgrade Pre-requisite patches must be applied before the first Live Upgrade Alternate Boot Environments are created (see "Pre-requisite Patches" section, below...) Solaris 10 Update 6 or newer on ZFS root is the practical starting point for Live Upgrade Live Upgrade with ZFS root is far more straight-forward than any scheme based on Alternative Boot Environments in slices or temporarily breaking mirrors Use Solaris best practices to upgrade the OS to at least Solaris 10 Update 4 (outside of Ops Center) UFS root can (technically) be used, but it is significantly more involved (e.g. discouraged) -- there are many reasons to move to ZFS while going through the process to update to Solaris 10 Update 6 or newer (out side of Ops Center) Recommendation: Start with Solaris 10 Update 6 or newer on ZFS root Recommendation: Start with Ops Center 12c or newer Ops Center 12c can automatically create your ABE's for you, without the need for custom scripts Ops Center 12c Update 2 avoids kernel panic on unpatched Solaris 10 update 9 (and older) -- unrelated to Live Upgrade, but more on the issue, below. NOTE: There is no magic!  If you have systems running Solaris 10 Update 5 or older on UFS root, and you don't know how to get them updated to Solaris 10 on ZFS root, then there are services available from Oracle Advanced Customer Support (ACS), which specialize in this area. Live Upgrade Pre-requisite Patches (Solaris 10) Certain Live Upgrade related patches must be present before the first Live Upgrade ABE's are created on Solaris 10.Use the following MOS Search String to find the “living document” that outlines the required patch minimums, which are necessary before using any Live Upgrade features: Solaris Live Upgrade Software Patch Requirements(Click above – the link is valid as of this writing, but search in MOS for the same "Solaris Live Upgrade Software Patch Requirements" string if necessary) It is a very good idea to check the document periodically and adapt to its contents, accordingly.IMPORTANT:  In case it wasn't clear in the above document, some direct patching of the active OS, including a reboot, may be required before Live Upgrade can be successfully used the first time.HINT: You can use Ops Center to determine what to expect for a given system, and to schedule the “pre-patching” during a maintenance window if necessary. Preparing to use Ops Center Discover + Manage (Install + Configure the Ops Center agent in) each Global Zone Recommendation:  Begin by using OCDoctor --agent-prereq to determine whether OS meets OC prerequisites (resolve any issues) See prior requirements and recommendations w.r.t. starting with Solaris 10 Update 6 or newer on ZFS (or at least Solaris 10 Update 4 on UFS, with caveats) WARNING: Systems running unpatched Solaris 10 update 9 (or older) should run the Ops Center 12c Update 2 agent to avoid a potential kernel panic The 12c Update 2 agent will check patch minimums and disable certain process accounting features if the kernel is not sufficiently patched to avoid the panic SPARC: 142900-05 Obsoleted by: 142900-06 SunOS 5.10: kernel patch 10 Oracle Solaris on SPARC (32-bit) X64: 142901-05 Obsoleted by: 142901-06 SunOS 5.10_x86: kernel patch 10 Oracle Solaris on x86 (32-bit) OR SPARC: 142909-17 SunOS 5.10: kernel patch 10 Oracle Solaris on SPARC (32-bit) X64: 142910-17 SunOS 5.10_x86: kernel patch 10 Oracle Solaris on x86 (32-bit) Ops Center 12c (initial release) and 12c Update 1 agent can also be safely used with a workaround (to be performed BEFORE installing the agent): # mkdir -p /etc/opt/sun/oc # echo "zstat_exacct_allowed=false" > /etc/opt/sun/oc/zstat.conf # chmod 755 /etc/opt/sun /etc/opt/sun/oc # chmod 644 /etc/opt/sun/oc/zstat.conf # chown -Rh root:sys /etc/opt/sun/oc NOTE: Remove the above after patching the OS sufficiently, or after upgrading to the 12c Update 2 agent Using Ops Center to apply Live Upgrade-related Pre-Patches (Solaris 10)Overview: Create an OS Update Profile containing the minimum LU-related pre-patches, based on the Solaris Live Upgrade Software Patch Requirements, previously mentioned. SIMULATE the deployment of the LU-related pre-patches Observe whether any of the LU-related pre-patches will require a reboot The job details for each Global Zone will advise whether a reboot step will be required ACTUALLY deploy the LU-related pre-patches, according to your change control process (e.g. if no reboot, maybe okay to do now; vs. must do later because of the reboot). You can schedule the job to occur later, during a maintenance window Check the job status for each node, resolving any issues found Once the LU-related pre-patches are applied, you can Ops Center to patch using Live Upgrade on Solaris 10 Using Ops Center to patch Solaris 10 with LU/ABE's -- the GOODS!(this is the heart of the tip): Create an OS Update Profile containing the patches that make up your standard build Use Solaris Baselines when possible Add other individual patches as needed ACTUALLY deploy the OS Update Profile Specify the appropriate Live Upgrade options, e.g. Synchronize the active BE to the alternate BE before patching Do not activate the BE after patching Check the job status for each node, resolving any issues found Activate the newly patched BE according to your change control process Activate = Reboot to the ABE, making the ABE the new active BE Ops Center does not separate LU activate from reboot, so expect a reboot! Check the job status for each node, resolving any issues found Examples (w/Screenshots) Solaris 10 and Live Upgrade: Auto-Create the Alternate Boot Environment (ZFS root only) ABE to be created on ZFS with name S10_12_07REC (Example) Uses built in feature to call “lucreate -n S10_12_07REC” behind scenes if not already present NOTE: Leave “lucreate” params blank (if you do specify options, the will be appended after -n $ABEName) Solaris 10 and Live Upgrade: Alternate Boot Environment Creation via Operational Profile (script) The Alternate Boot Environment is to be created via custom, user-supplied script, which does whatever is needed for the system where Live Upgrade will be used. Operational Profile, which provides the script to create an ABE: Very similar to the automatic case, but with a Script (Operational Profile), which is used to create the ABE Relies on user-supplied script in the form of an Operational Profile Could be used to prepare an ABE based on a UFS root in a slice, or on a separate device (e.g. by breaking a mirror first) – it is up to the script author to do the right thing! EXAMPLE: Same result as the ZFS case, but illustrating the Operational Profile (e.g. script) approach to call: # lucreate -n S10_1207REC NOTE: OC special variable is $ABEName Boot Environment Profile, which references the Operational Profile Script = Operational Profile on this screen Refers to Operational Profile shown in the previous section The user-supplied S10_Create_BE Operational Profile will be run The Operational Profile must send a non-zero exit code if there is a problem (so that the OS Update job will not proceed) Solaris 10 OS Update Profile (to provide the actual patch specifications) Solaris 10 Baseline “Recommended” chosen for “Install” Solaris 10 OS Update Plan (two-steps in this case) “Create a Boot Environment” + “Update OS” are chosen. Using Ops Center to patch Solaris 11 with Boot Environments (as needed) Create a Solaris 11 OS Update Profile containing the packages that make up your standard build ACTUALLY deploy the Solaris 11 OS Update Profile BE will be created if needed (or you can stipulate no BE) BE name will be auto-generated (if needed), or you may specify a BE name Check the job status for each node, resolving any issues found Check if a BE was created; if so, activate the new BE Activate = Reboot to the BE, making the new BE the active BE Ops Center does not separate BE activate from reboot NOTE: Not every Solaris 11 OS Update will require a new BE, so a reboot may not be necessary. Solaris 11: Auto BE Create (as Needed -- let Ops Center decide) BE to be created as needed BE to be named automatically Reboot (if necessary) deferred to separate step Solaris 11: OS Profile Solaris 11 “entire” chosen for a particular SRU Solaris 11: OS Update Plan (w/BE)  “Create a Boot Environment” + “Update OS” are chosen. Summary: Solaris 10 Live Upgrade, Alternate Boot Environments, and their equivalents on Solaris 11 can be very powerful tools to help minimize the downtime associated with updating your servers.  For very old Solaris, there are some important prerequisites to adhere to, but once the initial preparation is complete, Live Upgrade can be used going forward.  For Solaris 11, the built-in Boot Environment handling is leveraged directly by the Image Packaging System, and the result is a much more straight forward way to patch, and far fewer prerequisites to satisfy in getting there.  Ops Center simplifies using either approach, and helps you improve consistency from system to system, which ultimately helps you improve the overall up-time across all the Solaris systems in your environment. Please let us know what you think?  Until next time...\Leon-- Leon Shaner | Senior IT/Product ArchitectSystems Management | Ops Center Engineering @ Oracle The views expressed on this [blog; Web site] are my own and do not necessarily reflect the views of Oracle. For more information, please go to Oracle Enterprise Manager  web page or  follow us at :  Twitter | Facebook | YouTube | Linkedin | Newsletter

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  • Clean Code Developer & Certification in IT - MSCC 21.09.2013

    It was a very busy weekend this time, and quite some hectic to organise the second meetup on a Saturday for the Mauritius Software Craftsmanship Community (MSCC) but it was absolutely fun. Following, I'm writing a brief summary about the topics we spoke about and the new impulses I got. "What a meetup... I was positively impressed. At the beginning I thought that noone would actually show up but then by the time the room got filled. Lots of conversation, great dialogues and fantastic networking between fresh students, experienced students, experienced employees, and self-employed attendees. That's what community is all about!" Above quote was my first reaction shortly after the gathering. And despite being busy during the weekend and yesterday, I took my time to reflect a little bit on things happened and statements made before writing it here on my blog. Additionally, I was also very curious about possible reactions and blogs from other attendees. Reactions from other craftsmen Let me quickly give you some links and quotes from others first... "Like Jochen posted on facebook, that was indeed a 5+ hours marathon (maybe 4 hours for me but still) … Wohoo! We’re indeed a bunch of crazy geeks who did not realise how time flew as we dived into the myriad discussions that sprouted. Yet in the end everyone was happy (:" -- Ish on MSCC meetup - The marathon (: "And the 4hours spent @ Talking drums bore its fruit..I was doing something I never did before....reading the borrowed book while walking....and though I was not that familiar with things mentionned in the book...I was skimming,scanning & flipping...reading titles...short paragraphs...and I skipped pages till I reached home." -- Yannick on Mauritius Software Craftsmanship 1st Meet-up "Hi Developers, Just wanted to share with you the meetups i attended last Saturday - [...] - The second meetup is the one hosted by Jochen Kirstätter, the MSCC, where the attendees were Craftsman, no woman, this time - all sharing the same passion of being a developer - even though it is on different platforms(Windows - Windows Phone - Linux - Adobe(yes a designer) - .Net) - but we manage to sit at the same table - sharing developer views and experience in the corporate world - also talking about good practice when coding( where Jochen initiated a discussion on Clean Coding ) i could not stay till the end - but from what i have heard - the longer you stay the more fun you have till 1600. Developers in the Facebook grouping i invite you to stay tuned about the various developer communities popping up - where you can come to share and learn good practices, develop the entrepreneurial spirit, and learn and share your passion about technologies" -- Arnaud on Facebook More feedback has been posted on the event directly. So, should I really write more? Wouldn't that spoil the impressions? Starting the day with a surprise Indeed, I was very pleased to stumble over the existence of Mobile Monday Mauritius on LinkedIn, an association about any kind of mobile app development, mobile gadgets and latest smartphones on the market. Despite the Monday in their name they had scheduled their recent meeting on Saturday between 10:00 and 12:00hrs. Wow, what a coincidence! Let's grap the bull by its horns and pay them an introductory visit. As they chose the Ebene Accelerator at the Orange Tower in Ebene it was a no-brainer to leave home a bit earlier and stop by. It was quite an experience and fun to talk to the geeks over there. Really looking forward to organise something together.... Arriving at the venue As the children got a bit uneasy at the MoMo gathering and I didn't want to disturb them too much, we arrived early at Bagatelle. Well, no problems as we went for a decent breakfast at Food Lover's Market. Shortly afterwards we went to our venue location, Talking Drums, and prepared the room for the meeting. We only had to take off a repro-painting of the wall in order to have a decent area for the projector. All went very smooth and my two little ones were of great help. Just in time, our first craftsman Avinash arrived on the spot. And then the waiting started... Luckily, not too long. Bit by bit more and more IT people came to join our meeting. Meanwhile, I used the time to give a brief introduction about the MSCC in general, what we are (hm, maybe I am) trying to achieve and that the recent phase is completely focused on creating more awareness that a community like the MSCC is active here in Mauritius. As soon as we reached some 'critical mass' of about ten people I asked everyone for a short introduction and bio, just in case... Conversation between participants started to kick in and we were actually more networking than having a focus on our topics of the day. Quick updates on latest news and development around the MSCC Finally, Clean Code Developer No matter how the position is actually called, whether it is Software Engineer, Software Developer, Programmer, Architect, or Craftsman, anyone working in IT is facing almost the same obstacles. As for the process of writing software applications there are re-occurring patterns and principles combined with some common exercise and best practices on how to resolve them. Initiated by the must-read book 'Clean Code' by Robert C. Martin (aka Uncle Bob) the concept of the Clean Code Developer (CCD) was born already some years ago. CCD is much likely to traditional martial arts where you create awareness of certain principles and learn how to apply practices to improve your style. The CCD initiative recommends to indicate your level of knowledge and experience with coloured wrist bands - equivalent to the belt colours - for various reasons. Frankly speaking, I think that the biggest advantage here is provided by the obvious recognition of conceptual understanding. For example, take the situation of a team meeting... A member with a higher grade in CCD, say Green grade, sees that there are mainly Red grades to talk to, and adjusts her way of communication to their level of understanding. The choice of words might change as certain elements of CCD are not yet familiar to all team members. So instead of talking in an abstract way which only Green grades could follow the whole scenario comes down to Red grade level. Different story, better results... Similar to learning martial arts, we only covered two grades during this occasion - black and red. Most interestingly, there was quite some positive feedback and lots of questions about the principles and practices of the red grade. And we gathered real-world examples from various craftsman and discussed them. Following the Clean Code Developer Red Grade and some annotations from our meetup: CCD Red Grade - Principles Don't Repeat Yourself - DRY Keep It Simple, Stupid (and Short) - KISS Beware of Optimisations! Favour Composition over Inheritance - FCoI Interestingly most of the attendees already heard about those key words but couldn't really classify or categorize them. It's very similar to a situation in which you do not the particular for a thing and have to describe it to others... until someone tells you the actual name and suddenly all is very simple. CCD Red Grade - Practices Follow the Boy Scouts Rule Root Cause Analysis - RCA Use a Version Control System Apply Simple Refactoring Pattern Reflect Daily Introduction to the principles and practices of Clean Code Developer - here: Red Grade As for the various ToDo's we commonly agreed that the Boy Scout Rule clearly is not limited to software development or IT administration but applies to daily life in general. Same for the root cause analysis, btw. We really had good stories with surprisingly endings and conclusions. A quick check about who is using a version control system brought more drive into the conversation. Not only that we had people that aren't using any VCS at all, we also had the 'classic' approach of backup folders and naming conventions as well as the VCS 'junkie' that has to use multiple systems at a time. Just for the records: Git and GitHub seem to be in favour of some of the attendees. Regarding the daily reflection at the end of the day we came up with an easy solution: Wrap it up as a blog entry! Certifications in IT This is kind of a controversy in IT in general. Is it interesting to go for certifications or are they completely obsolete? What are the possibilities to get certified? What are the options we have in Mauritius? How would certificates stand compared to other educational tracks like Computer Science or Web Design. The ratio between craftsmen with certifications like MCP, MSTS, CCNA or LPI versus the ones without wasn't in favour for the first group but there was a high interest in the topic itself and some were really surprised to hear that exam preparations are completely free available online including temporarily voucher codes for either discounts or completely free exams. Furthermore, we discussed possible options on forming so-called study groups on a specific certificates and organising more frequent meetups in order to learn together. Taking into consideration that we have sponsored access to the video course material of Pluralsight (and now PeepCode as well as TrainSignal), we might give it a try by the end of the year. Current favourites are LPIC Level 1 and one of the Microsoft exams 40-78x. Feedback and ideas for the MSCC The closing conversations and discussions about how the MSCC is recently doing, what are the possibilities and what's (hopefully) going to happen in the future were really fertile and I made a couple of mental bullet points which I'm looking forward to tackle down together with orher craftsmen. Eventually, it might be a good option to elaborate on some issues during our weekly Code & Coffee sessions one Wednesday morning. Active discussion on various IT topics like certifications (LPI, MCP, CCNA, etc) and sharing experience Finally, we made it till the end of the planned time. Well, actually the talk was still on and we continued even after 16:00hrs. Unfortunately, we (the children and I) had to leave for evening activities. My resume of the day... It was great to have 15 craftsmen in one room. There are hundreds of IT geeks out there in Mauritius, and as Mauritius Software Craftsmanship Community we still have a lot of work to do to pass on the message to some more key players and companies. Currently, it seems that we are able to attract a good number of students in Computer Science... but we have a lot more to offer, even or especially for IT people on the job. I'm already looking forward to our next Saturday meetup in the near future. PS: Meetup pictures are courtesy of Nirvan Pagooah. Thanks for sharing...

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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  • Clean Code Development & Flexible work environment - MSCC 26.10.2013

    Finally, some spare time to summarize my impressions and experiences of the recent meetup of Mauritius Software Craftsmanship Community. I already posted my comment on the event and on our social media networks: Professional - It's getting better with our meetups and I really appreciated that 'seniors' and 'juniors' were present today. Despite running a little bit out of time it was really great to see more students coming to the gathering. This time we changed location for our Saturday meetup and it worked out very well. A big thank you to Ebene Accelerator, namely Mrs Poonum, for the ability to use their meeting rooms for our community get-together. Already some weeks ago I had a very pleasant conversation with her about the MSCC aims, 'mission' and how we organise things. Additionally, I think that an environment like the Ebene Accelerator is a good choice as it acts as an incubator for young developers and start-ups. Reactions from other craftsmen Before I put my thoughts about our recent meeting down, I'd like to mention and cross-link to some of the other craftsmen that were present: "MSCC meet up is a massive knowledge gaining strategies for students, future entrepreneurs, or for geeks all around. Knowledge sharing becomes a fun. For those who have not been able to made it do subscribe on our MSCC meet up group at meetup.com." -- Nitin on Learning is fun with #MSCC #Ebene Accelerator "We then talked about the IT industry in Mauritius, salary issues in various field like system administration, software development etc. We analysed the reasons why people tend to hop from one company to another. That was a fun debate." -- Ish on MSCC meetup - Gang of Geeks "Flexible Learning Environment was quite interesting since these lines struck cords : "You're not a secretary....9 to 5 shouldn't suit you"....This allowed reflection...deep reflection....especially regarding the local mindset...which should be changed in a way which would promote creativity rather than choking it till death..." -- Yannick on 2nd MSCC Monthly Meet-up And others on Facebook... ;-) Visual impressions are available on our Meetup event page. More first time attendees We great pleasure I noticed that we have once again more first time visitors. A quick overlook showed that we had a majority of UoM students in first, second or last year. Some of them are already participating in the UoM Computer Club or are nominated as members of the Microsoft Student Partner (MSP) programme. Personally, I really appreciate the fact that the MSCC is able to gather such a broad audience. And as I wrote initially, the MSCC is technology-agnostic; we want IT people from any segment of this business. Of course, students which are about to delve into the 'real world' of working are highly welcome, and I hope that they might get one or other glimpse of experience or advice from employees. Sticking to the schedule? No, not really... And honestly, it was a good choice to go a little bit of the beaten tracks. I mean, yes we have a 'rough' agenda of topics that we would like to talk about or having a presentation about. But we keep it 'agile'. Due to the high number of new faces, we initiated another quick round of introductions and I gave a really brief overview of the MSCC. Next, we started to reflect on the Clean Code Developer (CCD) - Red Grade which we introduced on the last meetup. Nirvan was the lucky one and he did a good job on summarizing the various abbreviations of the first level of being a CCD. Actually, more interesting, we exchanged experience about the principles and practices of Red Grade, and it was very informative to get to know that Yann actually 'interviewed' a couple of friends, other students, local guys working in IT companies as well as some IT friends from India in order to counter-check on what he learned first-hand about Clean Code. Currently, he is reading the book of Robert C. Martin on that topic and I'm looking forward to his review soon. More output generates more input What seems to be like a personal mantra is working out pretty well for me since the beginning of this year. Being more active on social media networks, writing more article on my blog, starting the Mauritius Software Craftsmanship Community, and contributing more to other online communities has helped me to receive more project requests, job offers and possibilities to expand my business at IOS Indian Ocean Software Ltd. Actually, it is not a coincidence that one of the questions new craftsmen should answer during registration asks about having a personal blog. Whether you are just curious about IT, right in the middle of your Computer Studies, or already working in software development or system administration since a while you should consider to advertise and market yourself online. Easiest way to resolve this are to have online profiles on professional social media networks like LinkedIn, Xing, Twitter, and Google+ (no Facebook should be considered for private only), and considering to have a personal blog. Why? -- Be yourself, be proud of your work, and let other people know that you're passionate about your profession. Trust me, this is going to open up opportunities you might not have dreamt about... Exchanging ideas about having a professional online presence - MSCC meetup on the 26th October 2013 Furthermore, consider to put your Curriculum Vitae online, too. There are quite a number of service providers like 1ClickCV, Stack Overflow Careers 2.0, etc. which give you the ability to have an up to date CV online. At least put it on your site, next to your personal blog. Similar to what you would be able to see on my site here. Cyber Island Mauritius - are we there? A couple of weeks ago I got a 'cold' message on LinkedIn from someone living in the U.S. asking about the circumstances and conditions of the IT world of Mauritius. He has a great business idea, venture capital and is currently looking for a team of software developers (mainly mobile - iOS) for a new startup here in Mauritius. Since then we exchanged quite some details through private messages and Skype conversations, and I suggested that it might be a good chance to join our meetup through a conference call and see for yourself about potential candidates. During approximately 30 to 40 minutes the brief idea of the new startup was presented - very promising state-of-the-art technology aspects and integration of various public APIs -, and we had a good Q&A session about it. Also thanks to the excellent bandwidth provided by the Ebene Accelerator the video conference between three parties went absolutely well. Clean Code Developer - Orange Grade Hahaha - nice one... Being at the Orange Tower at Ebene and then talking about an Orange Grade as CCD. Well, once again I provided an overview of the principles and practices in that rank of Clean Code, and similar to our last meetup we discussed on the various aspect of each principle, whether someone already got in touch with it during studies or work, and how it could affect their future view on their source code. Following are the principles and practices of Clean Code Developer - Orange Grade: CCD Orange Grade - Principles Single Level of Abstraction (SLA) Single Responsibility Principle (SRP) Separation of Concerns (SoC) Source Code conventions CCD Orange Grade - Practices Issue Tracking Automated Integration Tests Reading, Reading, Reading Reviews Especially the part on reading technical books got some extra attention. We quickly gathered our views on that and came up with a result that ranges between Zero (0) and up to Fifteen (15) book titles per year. Personally, I'm keeping my progress between Six (6) and Eight (8) titles per year, but at least One (1) per quarter of a year. Which is also connected to the fact that I'm participating in the O'Reilly Reader Review Program and have a another benefit to get access to free books only by writing and publishing a review afterwards. We also had a good exchange on the extended topic of 'Reviews' - which to my opinion is abnormal difficult here in Mauritius for various reasons. As far as I can tell from my experience working with Mauritian software developers, either as colleagues, employees or during consulting services there are unfortunately two dominant pattern on that topic: Keeping quiet Running away Honestly, I have no evidence about why these are the two 'solutions' on reviews but that's the situation that I had to face over the last couple of years. Sitting together and talking about problematic issues, tackling down root causes of de-motivational activities and working on general improvements doesn't seem to have a ground within the IT world of Mauritius. Are you a typist or a creative software craftsman? - MSCC meetup on the 26th October 2013 One very good example that we talked about was the fact of 'job hoppers' as you can easily observe it on someone's CV - those people change job every single year; for no obvious reason! Frankly speaking, I wouldn't even consider an IT person like to for an interview. As a company you're investing money and effort into the abilities of your employees. Hiring someone that won't stay for a longer period is out of question. And sorry to say, these kind of IT guys smell fishy about their capabilities and more likely to cause problems than actually produce productive results. One of the reasons why there is a probation period on an employment contract is to give you the liberty to leave as early as possible in case that you don't like your new position. Don't fool yourself or waste other people's time and money by hanging around a full year only to snatch off the bonus payment... Future outlook: Developer's Conference Even though it is not official yet I already mentioned it several times during our weekly Code & Coffee sessions. The MSCC is looking forward to be able to organise or to contribute to an upcoming IT event. Currently, the rough schedule is set for April 2014 but this mainly depends on availability of location(s), a decent time frame for preparations, and the underlying procedures with public bodies to have it approved and so on. As soon as the information about date and location has been fixed there will be a 'Call for Papers' period in order to attract local IT enthusiasts to apply for a session slot and talk about their field of work and their passion in IT. More to come for sure... My resume of the day It was a great gathering and I am very pleased about the fact that we had another 15 craftsmen (plus 2 businessmen on conference call plus 2 young apprentices) in the same room, talking about IT related topics and sharing their experience as employees and students. Personally, I really appreciated the feedback from the students about their current view on their future career, and I really hope that some of them are going to pursue their dreams. Start promoting yourself and it will happen... Looking forward to your blogs! And last but not least our numbers on Meetup and Facebook have been increased as a direct consequence of this meetup. Please, spread the word about the MSCC and get your friends and colleagues to join our official site. The higher the number of craftsmen we have the better chances we have t achieve something great! Thanks!

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  • Oracle Linux Tips and Tricks: Using SSH

    - by Robert Chase
    Out of all of the utilities available to systems administrators ssh is probably the most useful of them all. Not only does it allow you to log into systems securely, but it can also be used to copy files, tunnel IP traffic and run remote commands on distant servers. It’s truly the Swiss army knife of systems administration. Secure Shell, also known as ssh, was developed in 1995 by Tau Ylonen after the University of Technology in Finland suffered a password sniffing attack. Back then it was common to use tools like rcp, rsh, ftp and telnet to connect to systems and move files across the network. The main problem with these tools is they provide no security and transmitted data in plain text including sensitive login credentials. SSH provides this security by encrypting all traffic transmitted over the wire to protect from password sniffing attacks. One of the more common use cases involving SSH is found when using scp. Secure Copy (scp) transmits data between hosts using SSH and allows you to easily copy all types of files. The syntax for the scp command is: scp /pathlocal/filenamelocal remoteuser@remotehost:/pathremote/filenameremote In the following simple example, I move a file named myfile from the system test1 to the system test2. I am prompted to provide valid user credentials for the remote host before the transfer will proceed.  If I were only using ftp, this information would be unencrypted as it went across the wire.  However, because scp uses SSH, my user credentials and the file and its contents are confidential and remain secure throughout the transfer.  [user1@test1 ~]# scp /home/user1/myfile user1@test2:/home/user1user1@test2's password: myfile                                    100%    0     0.0KB/s   00:00 You can also use ssh to send network traffic and utilize the encryption built into ssh to protect traffic over the wire. This is known as an ssh tunnel. In order to utilize this feature, the server that you intend to connect to (the remote system) must have TCP forwarding enabled within the sshd configuraton. To enable TCP forwarding on the remote system, make sure AllowTCPForwarding is set to yes and enabled in the /etc/ssh/sshd_conf file: AllowTcpForwarding yes Once you have this configured, you can connect to the server and setup a local port which you can direct traffic to that will go over the secure tunnel. The following command will setup a tunnel on port 8989 on your local system. You can then redirect a web browser to use this local port, allowing the traffic to go through the encrypted tunnel to the remote system. It is important to select a local port that is not being used by a service and is not restricted by firewall rules.  In the following example the -D specifies a local dynamic application level port forwarding and the -N specifies not to execute a remote command.   ssh –D 8989 [email protected] -N You can also forward specific ports on both the local and remote host. The following example will setup a port forward on port 8080 and forward it to port 80 on the remote machine. ssh -L 8080:farwebserver.com:80 [email protected] You can even run remote commands via ssh which is quite useful for scripting or remote system administration tasks. The following example shows how to  log in remotely and execute the command ls –la in the home directory of the machine. Because ssh encrypts the traffic, the login credentials and output of the command are completely protected while they travel over the wire. [rchase@test1 ~]$ ssh rchase@test2 'ls -la'rchase@test2's password: total 24drwx------  2 rchase rchase 4096 Sep  6 15:17 .drwxr-xr-x. 3 root   root   4096 Sep  6 15:16 ..-rw-------  1 rchase rchase   12 Sep  6 15:17 .bash_history-rw-r--r--  1 rchase rchase   18 Dec 20  2012 .bash_logout-rw-r--r--  1 rchase rchase  176 Dec 20  2012 .bash_profile-rw-r--r--  1 rchase rchase  124 Dec 20  2012 .bashrc You can execute any command contained in the quotations marks as long as you have permission with the user account that you are using to log in. This can be very powerful and useful for collecting information for reports, remote controlling systems and performing systems administration tasks using shell scripts. To make your shell scripts even more useful and to automate logins you can use ssh keys for running commands remotely and securely without the need to enter a password. You can accomplish this with key based authentication. The first step in setting up key based authentication is to generate a public key for the system that you wish to log in from. In the following example you are generating a ssh key on a test system. In case you are wondering, this key was generated on a test VM that was destroyed after this article. [rchase@test1 .ssh]$ ssh-keygen -t rsaGenerating public/private rsa key pair.Enter file in which to save the key (/home/rchase/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/rchase/.ssh/id_rsa.Your public key has been saved in /home/rchase/.ssh/id_rsa.pub.The key fingerprint is:7a:8e:86:ef:59:70:ef:43:b7:ee:33:03:6e:6f:69:e8 rchase@test1The key's randomart image is:+--[ RSA 2048]----+|                 ||  . .            ||   o .           ||    . o o        ||   o o oS+       ||  +   o.= =      ||   o ..o.+ =     ||    . .+. =      ||     ...Eo       |+-----------------+ Now that you have the key generated on the local system you should to copy it to the target server into a temporary location. The user’s home directory is fine for this. [rchase@test1 .ssh]$ scp id_rsa.pub rchase@test2:/home/rchaserchase@test2's password: id_rsa.pub                  Now that the file has been copied to the server, you need to append it to the authorized_keys file. This should be appended to the end of the file in the event that there are other authorized keys on the system. [rchase@test2 ~]$ cat id_rsa.pub >> .ssh/authorized_keys Once the process is complete you are ready to login. Since you are using key based authentication you are not prompted for a password when logging into the system.   [rchase@test1 ~]$ ssh test2Last login: Fri Sep  6 17:42:02 2013 from test1 This makes it much easier to run remote commands. Here’s an example of the remote command from earlier. With no password it’s almost as if the command ran locally. [rchase@test1 ~]$ ssh test2 'ls -la'total 32drwx------  3 rchase rchase 4096 Sep  6 17:40 .drwxr-xr-x. 3 root   root   4096 Sep  6 15:16 ..-rw-------  1 rchase rchase   12 Sep  6 15:17 .bash_history-rw-r--r--  1 rchase rchase   18 Dec 20  2012 .bash_logout-rw-r--r--  1 rchase rchase  176 Dec 20  2012 .bash_profile-rw-r--r--  1 rchase rchase  124 Dec 20  2012 .bashrc As a security consideration it's important to note the permissions of .ssh and the authorized_keys file.  .ssh should be 700 and authorized_keys should be set to 600.  This prevents unauthorized access to ssh keys from other users on the system.   An even easier way to move keys back and forth is to use ssh-copy-id. Instead of copying the file and appending it manually to the authorized_keys file, ssh-copy-id does both steps at once for you.  Here’s an example of moving the same key using ssh-copy-id.The –i in the example is so that we can specify the path to the id file, which in this case is /home/rchase/.ssh/id_rsa.pub [rchase@test1]$ ssh-copy-id -i /home/rchase/.ssh/id_rsa.pub rchase@test2 One of the last tips that I will cover is the ssh config file. By using the ssh config file you can setup host aliases to make logins to hosts with odd ports or long hostnames much easier and simpler to remember. Here’s an example entry in our .ssh/config file. Host dev1 Hostname somereallylonghostname.somereallylongdomain.com Port 28372 User somereallylongusername12345678 Let’s compare the login process between the two. Which would you want to type and remember? ssh somereallylongusername12345678@ somereallylonghostname.somereallylongdomain.com –p 28372 ssh dev1 I hope you find these tips useful.  There are a number of tools used by system administrators to streamline processes and simplify workflows and whether you are new to Linux or a longtime user, I'm sure you will agree that SSH offers useful features that can be used every day.  Send me your comments and let us know the ways you  use SSH with Linux.  If you have other tools you would like to see covered in a similar post, send in your suggestions.

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