Linux Cheatsheet

by Aeon

Linux Cheatsheet

Basic commands

• cat: Dump the contents of a file to the screen. eg: 'cat ./foo'
• cd Change to another directory. eg: 'cd /bin'
• chmod Change a file's permissions. eg: 'chmod +r ./foo'
• chown Change a file's owner/group. eg: 'chown philipl.users ./foo'
• cp Copy a file to a new name/location. eg: 'cp ./foo /tmp/bar'
• grep Look for text in files. eg: grep "He's dead jim" *.txt"
• gzip/gunzip Compress/Uncompress a file. eg: "gzip foo"
• head/tail Dump the first/last few lines of a file. eg: 'tail ./foo'
• locate Find files by name. eg: 'locate ssh'
• ls Display the contents of a directory. eg: 'ls /bin'
• mkdir Make a directory. eg: 'mkdir bar'
• mv move a file to a new name/location. eg: 'mv ./foo /tmp/bar'
• pwd Print the current directory to the screen. eg: 'pwd'
• shutdown Shutdown/reboot the computer. eg: 'shutdown -r now'
• su Change to another user temporarily. eg: 'su root'
• tar Archive directories and their contents. eg: 'tar cf /tmp tmp.tar'
• rm Remove (delete) a file. eg: 'rm ./foo'


Getting Help
• man Read the manual page for a command. eg: 'man ls'
• apropos Read the one line summary for a command. eg: 'apropos ls'

Basic vi commands
• i Change to insert mode (so you can type)
•  Change to command mode (don't try and type)
• :w Save the file being edited (command mode only)
• :q Quit (command mode only)
• :q! Get me out of here now! (ignore unsaved work)
• h/j/k/l Navigation keys if your arrows break (command mode only)
(Try pressing scroll-lock first to try and make arrows work)

The basic parts of the filesystem
• /bin Basic programs
• /boot Bootloader files
• /dev Device nodes for hardware and other non-file resources
• /etc Configuration files
• /home Where everyone's home directory lives
• /lib Base system libraries
• /lost+found When your filesystem breaks, the pieces go here.
• /mnt Place to attach other filesystems (usually removable media)
• /opt Optional packages (usually just KDE)
• /proc Virtual filesystem for communication with the kernel
• /root Root's home directory (root is special)
• /sbin Basic programs that are usually only useful for root
• /tmp Temporary file storage area
• /usr 'User' files. Most stuff goes here. Programs in /usr/bin, libraries
in /usr/lib, program resources in /usr/share, etc.
• /var System and program state storage

Compiling programs from source (very general case)
• Unpack the source archive: tar zxf foo-1.0.tar.gz
• Go to source directory: cd foo-1.0
• Read README, INSTALL and output of ./configure --help
• Run configure: ./configure (if it fails, identify the error and try to correct it). The most
common error will be a missing program/library that is required for foo to work.
• Make the program: make
• Install the program: make install (This step usually has to be run as root, unless
installation is to the user's home directory)

Recompiling your kernel (very high level. Read up on this!)
• Goto the kernel source directory: cd /usr/src/linux
• Configure the kernel to your liking: make xconfig / make menuconfig
• Build the kernel: make bzImage
• Build the kernel modules: make modules
• Install the kernel modules: make modules_install
• Install the kernel: Very distribution dependent. The kernel itself is arch/i386/boot/bzImage
(unless you're on non-intel hardware) and should be copied to wherever your current
kernel lives (usually / or /boot).
• Update your bootloader to use the new kernel. For lilo, edit /etc/lilo.conf

Cool Programs to investigate (Character based/Command Line/Graphical)
•ssh/sftp/scp: Secure remote access and file transfer
•mozilla: Comprehensive web browsing and email handling package
•ncftp: FTP isn't secure, but ncftp does it the best
•evolution: Specialised enterprise-capable email program
•traceroute: Find out what's between you and another system
•galeon: The best web browser around! :-) (Trust us, Phil knows best)
•lynx/links: Text-mode web browsing
•gedit; Simple but extensible text editor
•naim: Text mode instant- messaging
•gaim: Slick multi-protocol instant messanger
•emacs: If it can't do it, you've run out of hd space
•OpenOffice.org: Fully featured office suite. Word-processing/Spreadsheets/Presentations
•nano/pico: Simple user friendly text editor. Shock!
•Abiword/Gnumeric: Standalone word-processor and spreadsheet programs.
•gcc/gdb: Compile and debug code
•xmms: Plugin based media player