Linux Notes

In case of catastrophic data loss or system failure, I've decided that it's safest for me to put a few notes in a public place. Some of these are distro-specific, so know that I use [K]Ubuntu and Fedora.

Bash Shortcuts (some of these actually libreadline shortcuts)

Ctrl-A Go to the beginning of the line you are currently typing on
Ctrl-E Go to the end of the line you are currently typing on
Ctrl-L Clears the Screen, similar to the clear command
Ctrl-U Clears the line before the cursor position. If you are at the end of the line, clears the entire line.
Ctrl-H Same as backspace
Ctrl-R Search history
Ctrl-C Stop whatever you are running via SIGINT
Ctrl-D Exit the current shell || Send EOF
Ctrl-Z Puts whatever you are running into a suspended background process. fg restores it.
Ctrl-W Delete the word before the cursor
Ctrl-K Clear (cut) the line after the cursor
Ctrl-Y Paste the cut from Ctrl-K
Ctrl-T Swap the last two characters before the cursor
Alt-T Swap the last two words before the cursor
Alt-F Move cursor forward one word on the current line
Alt-B Move cursor backward one word on the current line
Alt-. Gives you the last argument of the last command (pressing again goes further back)
Esc Last object. For example: cat /etc/fstab -> vi <esc> -> vi /etc/fstab

Useful Commands to know

Clear screen: $ clear
Show end of file: $ tail
Display routing table: $ netstat -rn
Add user to sudo: $ username -S sudo
Zip directory with password: $ zip -e -r myzipfile.zip dir/
Have Firestarter (or other service) start in runlevels 3, 4, and 5: $ chkconfig --levels 345 firestarter on
Check swap: # cat /proc/swaps
Check processors: # cat /proc/cpuinfo
Switch to English temporarily: $ export LANG=C
Symlinkng: $ ln -s /to/directory/name /from/directory/name
Changing file time: $ touch -d '3 Jan 2007 15:47:00' file.jpg
Find out top 10 directories eating up your disk space: # du -csh * –max-depth=0 | sort -rn | head -10
Find Harddisk Capacity on the box: # fdisk -l | grep -iE ‘mb|gb|tb’
Find out performance of hard disk: # hdparm -t -T /dev/hda
Tunnel GUI through ssh: $ ssh -X xxx.xxx.xxx.xx
Hardware Information: # dmidecode
Dell Fan Contro: # i8kctl
Find what version (and other info) of package is installed: $ dpkg -s packageName
ls in reverse-time order: $ ls -lrt
Change default web browser: $ sudo update-alternatives --config x-www-browser

Reset forgotten password

Add "rw init=/bin/bash" to the kernel line in grub.

# passwd username

Create an ISO image from CD

1. Insert CD, but do not mount. Verify if cd is mounted or not with mount command:

   # mount

2. If CD was mouted automatically unmout it with umount command:

   # umount /dev/cdrom

3. Create CD-ROM ISO image with dd command:

   # dd if=/dev/cdrom of=/home/user/cdimg.iso

Make and extract encrypted tarball from directory

$ tar -zcvf - folder/ | openssl des3 -salt -k PASSWORD | dd of=mybackup.tbz
$ dd if=mybackup.tbz | openssl des3 -d -k PASSWORD | tar zvxf -

Encrypt and extract tarball with openssl

$ openssl enc -aes-256-cbc -salt -in stuff.tar.gz -out stuff.tar.gz.enc -pass pass:PassWordHere
$ openssl enc -d -aes-256-cbc -in stuff.tar.gz.enc -out stuff.tar.gz

Extract different types of tarball

$ tar -xzf file.tar.gz
$ tar -xjf file.bz2

Mount an .iso

# mkdir /media/iso
# modprobe loop
# mount filename.iso /media/iso -t iso9660 -o loop

Delete a file securely, first overwriting it to hide its contents

$ shred -n 200 -z -u filename
$ srm filename
$ wipe filename

Forcefully unmount CD/DVD Rom or any other mounted partitions

# fuser -km /dev/cdrom

Spoof MAC Address

# ifconfig eth0 down
# ifconfig eth0 hw ether 00:00:00:00:00:00

Find and Kill processes

$ ps ux (processes owned by current user)
$ ps -e (all processes on machine)
$ kill 1234 (kill process #1234)
$ pkill firefox

Check Tempurature

$ cat /proc/acpi/thermal_zone/THM/temperature
$ acpi -V
$ sudo sensors

Search for files by content

$ find . -exec grep -q "search" '{}' \; -print     // print path of files that contain the text "search" recursively
$ grep "search" *    // print lines of files in pwd that contains the text "search"
$ grep -i "search" `find . -name "*" -print`    // print lines of files that contain the text "search" recursively and case insensitive
$ grep -i -n 'searchTerm' *    // Find files containing search terms

Date Published: 2008-05-08
Date Revised: 2008-07-17