Linux Desktop Fun: Summon Swarms Of Penguins To Waddle About The Desktop

Posted on in Categories Linux, Linux desktop last updated June 11, 2012

XPenguins is a program for animating cute cartoons animals in your root window. By default it will be penguins they drop in from the top of the screen, walk along the tops of your windows, up the side of your windows, levitate, skateboard, and do other similarly exciting things. Now you can send an army of cute little penguins to invade the screen of someone else on your network.

Howto: Verify Downloaded Linux / BSD DVD or CD ISO images for integrity

Posted on in Categories CentOS, Debian Linux, Howto, Linux, Linux distribution, RedHat/Fedora Linux, Security, Sys admin, Tip of the day, Ubuntu Linux, UNIX last updated July 26, 2007

You need to verify that that downloaded Linux DVD or ISO images are intact before you burn and use them. This is security feature. But how do you verify ISO images?

Answer is quite simple use md5sum command to compute and check MD5 message digest.

Why verify ISO images?

a) To protect yourself
b) Verify that a file has not changed as a result of file transfer, disk error, cracker attacks, etc.

How does it work?

When you run md5sum command on ISO file, you get checksum (or hash) on screen. You need to compare this checksum with original. It works as a compact digital fingerprint of a file. You can then compare the MD5 hash of your download ISO file, to the known good hash of the file you are checking. If the two values match, you are safe and use the ISO image.

Example

Let us download FreeBSD ISO image:
$ cd /tmp
$ wget ftp://ftp.freebsd.org/pub/FreeBSD/releases/i386/ISO-IMAGES/6.2/6.2-RELEASE-i386-bootonly.iso

Next download MD5 checksum:
$ wget ftp://ftp.freebsd.org/pub/FreeBSD/releases/i386/ISO-IMAGES/6.2/CHECKSUM.MD5

Generate MD5 hash for ISO image

$ md5sum 6.2-RELEASE-i386-bootonly.iso
Output:

4e8701ac951bc4537f8420fdac7efbb5  6.2-RELEASE-i386-bootonly.iso

Verify ISO image

See the known good hash of the file (6.2-RELEASE-i386-bootonly.iso):
$ md5sum -c CHECKSUM.MD5
Output:

6.2-RELEASE-i386-bootonly.iso: OK

You can also use following command for the same purpose:

A note for Windows XP / Vista users