• Difficulty: Easy
• Application: KStars

You may already have played with KStars, but how about creating a KStars backdrop image that’s updated every time you start up?

KStars can be run with the –dump switch, which dumps out an image from your startup settings, but doesn’t load the GUI at all. You can create a script to run this and generate a desktop image, which will change every day (or you can just use this method to generate images).

Run KStars like this:

kstars --dump --width 1024 --height 768 --filename = ~/kstarsback.png

You can add this to a script in your ~/.kde/Autostart folder to be run at startup. Find the file in Konqueror, drag it to the desktop and select ‘Set as wallpaper’ to use it as a randomly generated backdrop.

Open an SVG directly

• Difficulty: Easy
• Application: Inkscape

You can run Inkscape from a shell and immediately edit a graphic directly from a URL. Just type:

inkscape http://www.somehost.com/graphic.svg

Remember to save it as something else though!

Editing without an editor

• Difficulty: Intermediate
• Application: Various

Very long files are often hard to manipulate with a text editor. If you need to do it regularly, chances are you’ll find it much faster to use some handy command-line tools instead, like in the following examples.

To print columns eg 1 and 3 from a file file1 into file2, we can use awk:

awk '{print $1, $3}' file1 > file2

To output only characters from column 8 to column 15 of file1, we can use cut:

cut -c 8-15 file1 > file2

To replace the word word1 with the word word2 in the file file1, we can use the sed command:

sed "s/word1/word2/g" file1 > file2

This is often a quicker way to get results than even opening a text editor.

Backup selected files only

• Difficulty: Intermediate
• Application: tar

Want to use tar to backup only certain files in a directory? Then you’ll want to use the -T flag as follows. First, create a file with the file you want to backup:

cat >> /etc/backup.conf
# /etc/passwd
# /etc/shadow
# /etc/yp.conf
# /etc/sysctl.conf
EOF

Then run tar with the -T flag pointing to the file just created:

tar -cjf bck-etc-`date +%Y-%m-%d`.tar.bz2 -T /etc/backup.conf

Now you have your backup.

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If you are familiar with CentOS, you know that out of the box, it is not really designed as a desktop distribution. Stella changes all that, as it is primarily aimed at desktop users, while retaining the core enterprise features and capabilities of CentOS.

And you can see that just by looking at the package manager. The package categories tell you that everything you can find in CentOS is also available in Stella. Plus desktop applications that you will not find in any default installation of CentOS. For example, an application listed in the screen shot below, is ROSA Media Player (ROMP), the default media player in ROSA Desktop, a distribution based on Mandriva Linux.

Because it is loaded with desktop applications and media codecs not available in CentOS, you can play most audio and video file formats out of the box. Here it shows a favorite online video playing in Firefox.

The next few screen shots show what the desktop looks like and some of the applications accessible from the menu. This one shows installed Internet applications.

Installed Office applications.

Installed multimedia applications.

Updates manager.

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Selinux is good security feature of Linux stop you to execute malicious applications. But it need to disable when you need to run your self developed application. You can check the selinux status by using following command:

# cat /selinux/enforce

1

If it will show 1, that means selinux enforcing is enabled.

You can disable that selinux temporarily or permanently. Use following methods to disable it.

Disable Temporarily:

To disable selinux temporarily set the 0 to /selinux/enforce file.

# echo 0 > /selinux/enforce

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mkfifo /tmp/packet_capture

2. Second give the following ssh command on your terminal, to start the tcpdump on remote PC.

ssh hostname_or_ip_of_remote_pc "tcpdump -s 0 -U -n -w - -i eth0 not port 22" 
 > /tmp/packet_capture

3. Third & last step, give the following command to start the WireShark on your PC, which will read packets from the special FIFO file ‘/tmp/packet_capture’ at runtime.

wireshark -k -i /tmp/packet_capture

After giving the above command all the packets of remote pc’s eth0 will be visible on WireShark.

top is a handy utility for monitoring the utilization of your system. It is invoked from the command line and it works by displaying lots of useful information, including CPU and memory usage, the number of running processes, load, the top resource hitters, and other useful bits. By default, top refreshes its report every 3 seconds.

Most of us use top in this fashion; we run it inside the terminal, look on the statistics for a few seconds and then graciously quit and continue our work.

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