I got my DB2 database installation running on a Ubuntu 11.10 machine recently, and have documented the steps I carried out below. Downloading DB2 The express edition is free, and can be downloaded from Download DB2 Express-C. You’ll need to register for an IBM id if you don’t already have one. Extracting and installing Use the command tar -zvxf db2exc_975_LNX_x86.tar.gz to extract the gzipped file. Run the installer using sudo ./db2setup, and choose “Install a Product” on the left menu. The installation process is quite straightforward after this point. Troubleshooting libaio.so.1 ‘not found’ when running db2setup I faced the following problem when I ran the setup script: $sudo ./db2setup ERROR: The required library file libaio.so.1 is not found on[…] Here’s a cheat sheet of Eclipse shortcuts I’ve put together to help me work really fast with the IDE. The shortcuts have been categorized into two sections – one that most people know about, and another section that contains the lesser known ones. You should be able quickly scan through the first section, and learn any of the ones that you don’t currently know. The second section might take longer, and you may want to bookmark this page for future reference. Easy Shortcuts Search in files Use Ctrl–H to search in all files across the workspace or project. Open Resource Ctrl–Shift–R opens a resource quickly – without the time it spends for indexing. This makes it especially fast when you’ve just opened a workspace, in[…] The singleton design pattern in Java is one that I found over the years to be both tricky and interesting. There are many ways to break this pattern – and developers keep writing about different techniques to break it. One powerful way to break this pattern is to use reflection to access the private constructor and instantiate the class as many times as you want. The underlying idea is that you can call private members of any class using theAccessibleObject.setAccessible(true) reflection method. There are available techniques to prevent such reflection attacks. One of them is using the old way of writing your Singleton class, that is, not using lazy initialization, and, in addition to that, throwing an exception in the constructor[…] UPDATE (18th Nov, 2011): I carried out a clean installation from a USB drive, and no longer have the purple/blank screen problem while loading the 3.0.0-12-generic kernel. I can conclude that a problematic web upgrade process prevented the newer kernel from loading. Possible fixes are being discussed on various forums, but none of them have worked for me. I’ve been running Ubuntu 11.04 (Natty Narwhal) for several months and have been satisfied with the experience. In October 2011, the newest stable Ubuntu 11.10 version (Oneiric Ocelot) was announced. The upgrade to the new distro can be carried out by running the command: sudo do-release-upgrade You could also enable automatic updates, like I did, and have Natty Narwhal prompt you to[…] To enable Oracle’s Java plugin in your Linux browsers, just copy these lines into a script, and run it! JAVA_HOME=/usr/lib/jvm/jdk1.7.0 MOZILLA_HOME=~/.mozilla mkdir$MOZILLA_HOME/plugins ln -s $JAVA_HOME/jre/lib/i386/libnpjp2.so$MOZILLA_HOME/plugins Note: You may need to change the value of JAVA_HOME so that it correctly points to your installation of the JDK. 64-bit users will need to change the final line to: ln -s $JAVA_HOME/jre/lib/amd64/libnpjp2.so$MOZILLA_HOME/plugins If you’re a newbie, here’s how to run the script: Using your favorite editor, paste the contents of the script into a new file. Find out where Oracle Java is installed. This location has the directories “bin”, “lib”, and “jre”, among others. Replace the value of JAVA_HOME with the path to this folder, and save the file. This[…]

While working on the Oracle Application Framework, my Application module’s class file was behaving in a strange manner. When it was deployed on Apache and run, it was throwing the following Error: oracle.jbo.JboException: JBO-29000: Unexpected exception caught: java.lang.ClassFormatError, msg=oracle/apps/fnd/framework/test/updateAMImpl (Invalid pc in line number table) at oracle.jbo.common.ampool.ApplicationPoolImpl.doCheckout(ApplicationPoolImpl.java:1619) at oracle.jbo.common.ampool.ApplicationPoolImpl.useApplicationModule(ApplicationPoolImpl.java:2366) at oracle.jbo.common.ampool.SessionCookieImpl.useApplicationModule(SessionCookieImpl.java:427) at oracle.jbo.http.HttpSessionCookieImpl.useApplicationModule(HttpSessionCookieImpl.java:214) at oracle.apps.fnd.framework.webui.OAHttpSessionCookieImpl.useApplicationModule(OAHttpSessionCookieImpl.java:473) at oracle.jbo.common.ampool.SessionCookieImpl.useApplicationModule(SessionCookieImpl.java:398) I Googled on this error a lot, but most of the suggested solutions spoke about compiling the class with a different JDK or a different Java version and deploying it again. I tried to do that, but the error persisted. Decompiling using javap I thought of decompiling the deployed class using the javap utility – if it would fail to decompile, that would[…]

Update (Nov 9, 2011): As noted in the comments below, Windows Services for UNIX Version (SFU) is no longer supported on Windows 7 and 2008. For these versions, try installing Cygwin with the optional nfs-server component. If you’re using Windows 2008, you can use the Server for NFS that comes built-in instead – in this case, most of the steps below should apply. A few days ago, I needed to share a large folder present on a Windows server to access it from my local Ubuntu workstation. I initially used Samba, but my build script refused to recognize paths present in that share. The solution was to use an NFS share – but this required a special setup on Windows.[…]

There are just three simple steps needed to automate your SSH/SFTP logins to remote Unix/Unix-like servers from your Ubuntu/Linux distribution, or an emulator on Windows like Cygwin. 1) Run ssh-keygen abdullah@desktop:~$ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/home/abdullah/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/abdullah/.ssh/id_rsa. Your public key has been saved in /home/abdullah/.ssh/id_rsa.pub. The key fingerprint is: 06:23:fc:34:0f:12:40:b2:5e:7c:41:eb:4f:a2:ab:24 abdullah@desktop The key’s randomart image is: 2) Run ssh-copy-id <username>@<server-name> abdullah@desktop:~$ ssh-copy-id login@myserver.com login@myserver.com’s password: Now try logging into the machine, with “ssh ‘login@myserver.com'”, and check in: ~/.ssh/authorized_keys to make sure we haven’t added extra keys that you weren’t expecting. 3) Login to your server using ssh[…]

To delete or remove a directory in Linux, use the “-r” flag to the “rm” command. “r” stands for recursive. rm -r <directory_name> On some Linux systems, you might be prompted before each file is deleted. This means that the rm command has been aliased to “rm -i”, which turns on interactive mode. To run the original rm command and avoid the prompts, use “\rm”: \rm -r <directory_name> In the bash shell, just as the backslash is used to escape special characters, it is also used to escape aliases. Caution! Be careful to double check the directory name you provide, and be extra careful when using wildcards. There have been many stories of grief because of users ending up deleting important files[…]

Flipkart is often called the Amazon of India. Set up by two ex-Amazon employees as a startup in 2007, it brings Indians the best of the online shopping world knocking at their doors. I’ve been a regular buyer of stuff from Flipkart, and my experience with them has been simply amazing. So here’s my review on Flipkart, and what I believe has been helping them to be highly successful. 1) They provide an estimated delivery time – and keep their promises Flipkart does not think short term by providing overly optimistic delivery times. Online stores will ensure returning customers only if they keep their promises, and Flipkart seems to keep that in mind with their fairly accurate delivery time estimates.[…]