Basic Linux Commands

Console Commands
Utility or Command Use/Description
passwd Changes password
nslookup Queries Internet domain name servers
quota Displays disk usage and limits
motd Message of the Day
finger username User information lookup program
man or xman command Displays pages of online manual
xman Displays System Manual in X
less filename or more filename Displays the contents of a file in the terminal one page at a time
info Displays information and documentation on shells, utilities and programs
clear Clears the terminal window
ls directory List contents of a directory
cat filename Displays the contents of a file in the terminal
rm filename Removes a file
pico filename or emacs filename Opens and edits text files
cp sourcefile detstinationfilename Copies a file
lpr filename Sends file to printer
grep string filename looks through files for strings
head filename Displays first 10 lines of file
tail filename Displays last 10 lines of file
mv existingfilename newfilename Moves or renames file
lpq filename Displays files in printing queue
lprm filename Removes file from printing queue
sort filename Displays and sorts file contents
diff filename1 filename2 Displays differences between files
file filename Displays information about file contents
echo string Copies string to terminal
date Displays current date and time
cal Displays calendar
gzip filename Compresses a file
compress filename Compresses a file
gunzip filename Decompresses a compressed file
zcat filename Displays contents of a compressed file
apropos command Lists all man page titles/headers that contain the command
lynx Text based web browser
dmesg Displays kernel ring buffer
which command Displays path to command
whereis command Displays paths to locations of commands
who Lists currently logged on users
finger username@hostname Obtains detailed information about a user currently using the system
w Lists currently logged on users with processing usage
mesg y/n Sets options for letting other users write you messages
write user Sends message to other users
talk user Allows two way chat to other users
chmod permissions filename Changes file access permissions
mkdir directoryname Makes a directory
rmdir directoryname Removes an empty directory
ln existingfile new-link Creates link to an existing file (hard link)
stat filename Lists information about a file
ln -s existingfile new-link Creates link to an existing file (soft link)
df Displays all mounted filesystems
ps Reports process status
command & Sends a job to the background (job: one or more commands connected by a pipe "|" or pipes) The operating system assigns a number to the job when you press return. example: [1] 3578
top Displays updating list of currently running processes
tty Displays the name of the terminal in which the command was issued
command > filename Redirects standard output 
command < filename Redirects standard input
cat file1 >> file2 Appends standard output from file1 to file2
cat /dev/null > filename or filename > /dev/null Redirects "bit bucket" or null string to file (only superuser has write access to this file)
command1 | command2 Pipe sends standard output of one command to the standard input of another command
tr string1 string2 < inputfile translates each character in string1 to the corresponding character in string2
command | tee filename | grep string Sends the output of one command to standard output and a file
bg %job number Sends job to the background by job number
fg %job number Brings job to the foreground by job number
kill PID or %job number Aborts a process by PID (Process Identification Number) or job number
jobs Displays a list of current jobs
netcfg Utility to set up PPP and network configurations
xev Utility used to see information flow from X server to client
echo $DISPLAY Environment variable that displays the ID string for a window
echo $PATH Variable that displays executable path
netstat Displays network connections
viewres Graphical class browser for X
xbill Game featuring Bill Gates trying to put windows on Macs and NeXT workstations
xevil Game similar to Loderunner?
xchomp Linux's version of PacMan
xcmap Strange color lookup utility
xedit Text editor for X
asclock Clock from AfterStep
xconsole Strange console for X
xmessage message Sends message to a dialog box
xgal XGalaga game
xg3 Image viewing program
xgc Graphing calculator?
xjewel Jewel game for Linux
xkbvleds LEDs?
xkbwatch LEDs?
xlogo Displays X logo
xmixer Opens system sound controls
xsnow Snowflakes are fallin' on your desktop
xwininfo Displays info about a window
startx Starts an X Window System server
ghostview Starts a text preview application
xv filename Image viewer
xsetroot -color Set background color in X
xcalc Starts a calculator in X
xclipboard Starts a clipboard in X
traceroute host Prints the route packets take to the host
hostname Displays system identity name
rlogin host Utility to connect to a remote system
telnet host Utility to connect to a remote system (similar to rlogin but more interactive)
rcp file remotemachine Used to copy from a remote computer
ftp Utility to transfer files between systems on a network
rsh command Utility to run a command on a remote system without logging in
ping host Utility used to test connection to a remote system
lcd directorypath Changes local machine directory while logged on to remote machine

 

Shared Directories
Directory Description
/ Root - The root directory is present in all Linux system file structures. It's the parent of all files in the system.
/bin Essential common binaries - Holds files needed to boot the system and run it when it comes up in single user mode.
/boot Static files of the boot loader.
/dev Device files - All files that represent peripheral devices.
/etc Machine-local system configuration - Holds administrative, config, and other system files. Holds /etc/passwd file that contains a list of all users who have permission to the system.
/home User home directories - Contains each user's or client's home directory
/lib Shared libraries
/mnt Mount point for temporary partitions
/proc Kernel and process information (virtual filesystem)
/root Home directory for root
/sbin Essential system binaries - Contains utilities for system administration.
/tmp Temporary files
/usr Second major hierarchy - Includes subdirectories that contain information used by the system.
/var Variable data - Contains files whose contents change as system runs.

 

vi Commands
Command Description
vi filename Starts vi and creates a new file
:q! Quits vi without saving work
p Pastes data in buffer below current line
P Pastes data in buffer above current line
yy Copies current line
:r !command Reads in output of the command
i Puts vi in insert mode
:set autoindent Sets vi to indent automatically
:set showmatch Sets vi to show matching parenthesis
:set nu Sets vi to display line numbers
:set showmode Sets vi to display the mode you're in
ESCAPE Sets vi to command mode
Control-U Erases current line (insert mode)
Control-H Erases on letter (insert mode)
Control-W Erases current word (insert mode)
h, j, k, l Moves cursor left, up, down, right respectively
u Undoes last action
x Deletes a single character
dw Deletes a single word
dd Deletes a single line
ZZ Writes work buffer to disk and exits vi
o inserts line after cursor position
Control-L Redraws screen
:w filename Save work as filename and exits

 

Control Characters
Key Use
Control-H or BACKSPACE Erases a character on the command line
Control-U Deletes an entire command line
Control-W Erases a word on the command line
Control-C Aborts program execution
COMMAND-Tab Switches Programs
Control-L or CONtrOL-R Refreshes the screen
Control-D, logout or exit Logs you off the system