Deleting a file that has been opened by another process in linux does not free up disk space. Running the df or du commands will indicate conflicting results. Closing / killing the process that opened the files will release the space on the disk. The lsof command can help you track, say the top ten open files in your OS sorted by disk space. If you ever run into trouble with large open files, use the following command

Top ten open files:
lsof / | awk ‘{if($7 > 1048576) print $7/1048576 “MB” ” ” $9 }’ | sort -n -u | tail

Output:

3.8054MB /usr/lib/libgtk-x11-2.0.so.0.2200.0
4.28024MB /usr/share/icons/hicolor/icon-theme.cache
8.17912MB /usr/lib/locale/locale-archive
8.86022MB /var/lib/apt/lists/lk.archive.ubuntu.com_ubuntu_dists_maverick_main_binary-i386_Packages
11.4047MB /usr/lib/flashplugin-installer/libflashplayer.so
14.6893MB /usr/lib/firefox-3.6.10/libxul.so
15.6504MB /var/cache/apt/pkgcache.bin
27.4744MB /var/lib/apt/lists/lk.archive.ubuntu.com_ubuntu_dists_maverick_universe_binary-i386_Packages
34.6615MB /usr/share/icons/gnome/icon-theme.cache
44.1719MB /home/user/.mozilla/firefox/tnrqzpro.default/urlclassifier3.sqlite

You can also lookup open files based on pid / port number. I hope the script saves you some time, should you ever find yourself in this situation.

One of the things I hear often from someone wanting to try linux and leave windows is that they are afraid that they will no longer be able perform some of the things they used to do. That is so wrong. Be it from the perspective of a developer or a casual user linux offers a wide range of apps to suit your needs. Here is a table of things I used to do in windows that I can still do in linux

Application	Windows	Suse Linux – KDE desktop
Chat	Gtalk, Skype	Kopete / pidgin for gtalk Skype is supported
Development	Eclipse / myeclipse / Netbeans	All of them have linux flavours
Screenshot	Gadwin printscreen	Ksnapshot
Browsing	Chrome / Firefox / Opera	They are all supported. Chrome support is getting better
SQL Client	Squirrel SQL	Supported. Java runs anywhere
Application server	Tomcat / Glassfish	Supported
Web server	Apache	Supported
Video player	DivX , VLC	VLC is supported
Package management	None	Yast,yum, apt etc etc
Firewall	Inbuilt / Zone alarm	IP Tables. Much more flexible
Database	Postgres	Supported
Desktop customization	Not bad	Amazing. You can add widgets, multiple panels etc etc
Multiple desktop support	No	Yes
Dual screen / Nvidia drivers	Yes	Yes
Remote desktop	Windows / VNC	Supported
Windows applications	Yes (Duh)	Simulate with WINE
Office	Windows office	Open office. Not great but ok. You can use an online office suite if needed.

Application	Windows	Linux
Chat	Gtalk, Skype	Kopete / pidgin for gtalk Skype is supported
Development	Eclipse / myeclipse / Netbeans	All of them have linux flavours
Screenshot	Gadwin printscreen	Ksnapshot
Browsing	Chrome / Firefox / Opera	They are all supported. Chrome support is getting better
SQL Client	Squirrel SQL	Supported. Java runs anywhere
Application server	Tomcat / Glassfish	Supported
Web server	Apache	Supported
Video player	DivX , VLC	VLC is supported
Package management	None	Yast,yum, apt etc etc
Firewall	Inbuilt / Zone alarm	IP Tables. Much more flexible
Database	Postgres	Supported
Desktop customization	Not bad	Amazing. You can add widgets, multiple panels etc etc

The list above is just a sample of the applications I use. I am sure there are more use cases.

I use remote linux services often and exposing them as local services can be performed securely using SSH. For example you can access a tomcat server or email server hosted at IP 1.2.3.4 by opening a secure SSH tunnel between your local machine and the target address – 1.2.3.4.

The OpenSSH tool can be used to perform SSH related activities on your machine. Simply install it with yum, apt-get or Yast, if it is not already available. Once you have it use the following command to open multiple SSH tunnels to your services

Open tunnel and execute commands:

ssh 1.2.3.4 -lmyUser -L 3098:1.2.3.4:21 -L 3099:1.2.3.4:80 -L 3100:1.2.3.4:443

The command is explained below

1.2.3.4 – Your target IP

l – The user to login as

L – A local tunnel to a remote port

3098 – The local port to use when establishing this tunnel

21 – The remote port at 1.2.3.4 to which the tunnel will be established

Multiple tunnels can be opened by specifying multiple -L flags. For example http://localhost:3099 will now redirect to http://1.2.3.4:80/ That is a fancy way of saying all HTTP requests ( 80 is the default port ) for 1.2.3.4 can now be reached locally at port 3099.

Note that the above command will also log you into the remote system. If you want to open the tunnels alone, use the -N switch and the -f switch as shown below

Open tunnels only:

ssh -f myUser@1.2.3.4 -L 3099:1.2.3.4:25 -N

The -f switch asks SSH to work in the background and -N asks SSH not to execute any commands.

I have been wanting to move to a linux based environment for java development for quite a while now. Many PROD servers I deploy to run on a linux distro. So testing configuration / code changes becomes easier when you have multiple DEV environments. I deploy to CentOS among other linux flavors. I have settled on the Open  Suse 11.2 desktop. Here are some things I liked

1. Open Suse managed to detect my Nvidia driver with Yast. I guess they teamed up with Nvidia to host a repository for linux drivers. I didnt have to download kernel sources or devels to enable dual monitor support (Which is otherwise required). Nice !
2. PPP over internet setup was pretty easy. Kinternet and the Yast configuration settings together let me connect to the net with ease.
3. Community support seems good. The Suse forums are alive and kicking.
4. In general there was software by default on the desktop that turned out to be very useful. I didn’t have to download extra components unless it was specific to my hardware, like a specialized driver.  ksnapshot for example is a cool way to capture screenshots.

I am yet to try out Ubuntu. For some reason it does not detect all my hardware so it fails to install If you are still using windows to develop in java here are a few reasons you should switch

1. Looks good on your resume. Learning to work with another OS / Desktop can broaden your perspective on getting things done.
2. Not as many viruses.
3. No IE
4. If you are someone that loves the command line client, you will enjoy getting things done quickly with the shell console.
5. Firewall configuration is pretty flexible and can be bent into any shape you want provided you know what you are doing.
6. Automatic updates managed by a package manager
7. You can switch to multiple workspaces to manage your windows.
8. etc etc.

That said I did find some minor annoyances.

1. No IE. Whether I like it or not some users still use IE to access some of my apps. So my selenuim based RC test cases will not fire the IE window anymore. I have to use tools like BrowserShots or Adobe’s BrowserLab to get things done.
2. Some applications require me to run a .exe file as a plugin. This is very rare but can be overcome by simulating programs on Wine.
3. Learning new shortcuts can be a pain. So if you feel frustrated dont give up. Remember that you had to do the same with windows when you started out. So it will ease with time.

I am able to do everything that I used to do with windows and there are free tools  that support just about any software function you can think of.  Not being able to find the tools / software you need is just a myth. Almost any function you can think of that you are currently using in windows, is supported under linux. Make the switch and enjoy the stability of linux. Use another distro besides Open Suse ? Feel free to leave a comment.