linux
How to Create an MD5 on Linux with md5sum
An MD5 hash is a one way verification sum which can be used to verify a string or contents of a file. Once you have a file and an MD5 checksum, the recipient of the file can also perform an MD5 calculation to ensure that the file’s contents are unchanged. They may have been changed [...]
How to umount when the device is busy
You need to unmount a CD or you want to pack away the external drive but when you try to umount it you get the dreaded “device is busy†message. Wouldn’t it be great if Linux actually told you what was keeping the drive busy? Here we are in 2008, I’m using Ubuntu Gutsy, and [...]
How To Install yum On RHEL System
There are more than a couple of ways of updating Red Hat Enterprise Linux (RHEL) packages on your machine. One is by using up2date, the default package updater of RHEL systems. Unlike Fedora and CentOS which uses yum, up2date requires you to be registered to Red Hat Network (RHN) to be able to download or [...]
How to display files in Linux Systems
There are 4 useful ways to display the contents or portions of a file. The first is the very commonly used command cat. For example, to display my list of object-oriented keywords used in this course, type: $ cat /home/public/cs601/oo.keywords.txt If a file is really big, you will probably want to use more, which spits [...]
How to make a histogram In Linux
A histogram is set of count, value pairs indicating how often the value occurs. The basic operation will be to sort, then count how many values occur in a row and then reverse sort so that the value with the highest count is at the top of the report. $ … | sort |uniq -c|sort [...]
How to kill a set of processes in Linux
If you want to kill all java processes running for parrt, you can either run killall java if you are parrt or generate a “kill” script via: $ ps auxwww|grep java|grep parrt|awk ‘{print “kill -9 “,$2;}’ > /tmp/killparrt $ bash /tmp/killparrt # run resulting script The /tmp/killparrt file would look something like: kill -9 1021 [...]
How to get command help in Linux
If you need to know about a command, ask for the “man” page. For example, to find out about the ls command, type $ man ls LS(1) System General Commands Manual LS(1) NAME ls – list directory contents SYNOPSIS ls [-ACFLRSTWacdfgiklnoqrstux1] [file ...] DESCRIPTION For each operand that names a file of a type other [...]
How to check the positioning of a site on Google from the command line
The calculation of the ranking of a site on Google is for an expert SEO ‘operation of fundamental importance in their activities for the optimization of websites. Think of manually calculating and verifying placement on search engines is quite difficult and laborious, which is why literally depopulated networking tools that promise to pay to automate [...]
How to Hide Files Inside An Image in Linux
Get an image file and an archive of the files that you want to hide. In this example, I have cat beer_and_cig.jpg and hideme.zip file. The zip file contains an MP3 song that I have stored inside the archive. To create the archive-image file, run this command: cat beer_and_cig.jpg hideme.zip > ucantseeme.jpg What this does [...]
How to Move files between machines in Linux
rsync When you need to have a directory on one machine mirrored on another machine, use rsync. It compares all the files in a directory subtree and copies over any that have changed to the mirrored directory on the other machine. For example, here is how you could “pull” all logs files from livebox.jguru.com to [...]
How to record your Skype calls on Linux
Skype Call Recorder is an open source tool that allows you to record your Skype calls on Linux. Current features include: Record calls to MP3, Ogg Vorbis or WAV files Automatic and manual recording Configure automatic recording on per-caller basis Split stereo recording Completely free, unlimited and open source, released under the GNU GPL For [...]
How to determine your free disk space in Linux
The first command we’ll look at is the “df†command. It comes bundled with all distributions of Linux. “df†stands for “disk freeâ€. It gives you a reading of the state of all your partitions. It gives you the total disk space, the used space, the space available, and then the percentage of space being [...]
Safe Way to Exit During Linux System Freezes
Linux Keyboard Shortcuts: Safe Way to Exit During System Freezes In Windows, when your system hangs, you can always press Ctrl-Alt-Delete, wait for the Task Manager to open, and kill the process that doesn’t respond. However, Ctrl-Alt-Delete don’t always work the way you want it to leaving you no other option but to do a [...]
How to check the version of a Linux OS
Console Command: uname -a is a linux command that will output useful information about your linux distribution, kernel version, cpu information and more. Example Output Linux computerName 2.6.22.18-desktop-1mdv #1 SMP Mon Feb 11 13:53:50 EST 2008 i686 Intel(R) Pentium(R) 4 CPU 3.40GHz GNU/Linux
How to clear the cache from memory in Linux System
I am having 4 gb of ram in my production systems. and normally after 24 hours my nagios gives warning for insufficient memmory. when we check systems ,it always shows the memory in cache. So we normally reboot the system to clear the cache from the memory till we find the following command. Linux Command [...]