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Linux Command Reference Index ( GNU / linux kernel 2.4.18-3, 2.4.18-14, 2.4.20-6 and 3.0.0-32-generic (Ubuntu) )*   
Linux is a registered trademark of Linus Torvalds

These are just a few of the most common GNU / Linux commands that you may find yourself looking for, along with some answers to common questions about running Linux. On most systems more information about a command can be found by typing [ man command ] ; man being the word man and command being the particular command you are checking.
You will need to be root to use some of these commands ; also be sure to check your path. If there is no path to the command then you will likely get a " command not found " error. Check the command to be sure you have typed it correctly. Be extremely careful as root , you can make your system unusable. This is very important to understand. If you are using a dual boot system you may not be able to access either system if you make a mistake as root and your system is not bootable. Before you type any command as root be absolutely certain of what you are doing. Any comments are encouraged and welcome at
  

Update June 19, 2013: I have checked all of the "Linux Commands" listed running Ubuntu Oneiric 11.10. The Kernel I am using is ( 3.0.0-32-generic ). The commands that did not work were: cjpeg,doexec,gtar,httpd,mail,manweb,pine,rpm,rvi,slocate,switchdesk,set gid,set uid, untar.

Update December 21, 2014: I have checked all of the "linux Commands" listed below running Ubuntu 12.04.5 LTS (Precise).    3.11.0-26-generic #45~precise1-Ubuntu SMP Tue Jul 15 04:02:35 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
The commands that did not work are: doexec, gtar, httpd, manweb, pine, rvi, slocate, switchdesk, traceroute, unset gid, unset uid, untar.

Please note that some of the commands may refer to programs not yet installed on your machine. Ubuntu will ask you if you want to install a program usually rather than just give you a "command not found" message For example when I typed the command "quota" (without the quotes and after I pressed enter, of course) I got this:
The program 'quota' is currently not installed. You can install it by typing: sudo apt-get install quota
You will then be asked to type your password (the admin password) and the installation will proceed (after you press enter) (this assumes you have an active internet connection).



First posted 2002-10-14
page last modified   2014-12-21


 Linux Commands
A   B   C   D   E   F   G   H   I   K   L   M   N   P   Q   R   S   T   U   V   W   XYZ
References and answers
back to beginning

A
alias  Create your own name for a command
arch  print machine architecture
ash  ash command interpreter (shell)
awk (gawk)  pattern scanning and processing language


B
basename  Remove directory and suffix from a file name
bash  GNU Bourne-Again Shell
bsh  Command interpreter (Shell)
bc  Command line calculator
bunzip2  Unzip .bz2 files


C  back to commands top
cat  Concatenate a file print it to the screen
chgrp  Change the group designation of a file
chmod  Change file permissions
chown  Change the owner of a file
cjpeg  Compress an image file to a JPEG file
clear  Clear terminal screen (command line)
comm  Compare two sorted files
stty cooked  Formatting the display of text in a terminal
cp  Copy command
cpio  Copy files to and from archives
csh  C Shell
cut  Print selected parts of lines to standard output


D  back to commands top
date  Display date and time
dc  Command line calculator
df  Show amount of disk space free
diff  Determine difference between two files
diff3  Determine difference between 3 files
dig   Interrogate DNS name servers
djpeg  Decompress a JPEG file to an image file
dmesg  Print or control the kernel ring buffer (print out bootup messages)
dnsdomainname  Show the system's DNS domain name
doexec  Run an executable with an arbitrary argv
domainname  Show or set the system's NIS/YP domain name
dos2unix  Converts plain text files in DOS/MAC format to UNIX format
du  Show disk useage
dumpkeys  Write keyboard driver's translation tables to std output


E  back to commands top
echo  Display a line of text
ed  Line-oriented text editor
egrep  Print lines matching a pattern
elinks  A text mode WWW browser (supports frames)
env  Dislay the path
ex  Start Vim in ex mode
eject  Eject media from device ( command line )


F  back to commands top
factor  Display prime factors of a number
false  Exit with a status code indicating failure
fdisk  The fdisk command with usage examples
fgrep  Variant of grep
find  Find a file
finger  Displays information about the system users
fixps  Try to fix common PostScript problems that break postprocessing
free  Display free memory


G  back to commands top
grep  Search for a pattern using regular expression
gtar  See the tar command
gunzip  Unzip .gz files
gzip  Compress using Lempel-Ziv coding (LZ77)


H  back to commands top
halt  Stop the system
hdparm  Get/set harddisk parameters
head  Print the first 10 lines of a file to standard output
hostname  Show or set the system's host name
history  Display entire command history
HISTSIZE  Change history size
httpd  Start Apache


I  back to commands top
identify  Describes the format and characteristics of image files.
id  Print information for username, or the current user
ifconfig  Display network and hardware addresses
igawk  Gawk with include files
ipcalc  Calculate IP information for a host


K  back to commands top
kbd_mode  Report or set the keyboard mode (RAW, MEDI- UMRAW or XLATE)
kill  Terminate a process


L  back to commands top
last  Show listing of last logged in users
lastlog  Formats and prints the contents of the last login log /var/log/lastlog file
link  Call the link function to create a link to a file
links  See elinks
ln   Create a link to the specified TARGET with optional LINK_NAME
loadkeys  Load keyboard translation tables
locate  Locate a file
login  Sign on
look  Displays any lines in file which contain "string" as a prefix.
ls  List directory contents
lsmod  List loaded kernel modules
lynx  Command to start the Lynx browser


M  back to commands top
mac2unix  Converts plain text files in DOS/MAC format to UNIX format
mail  A mail processing system, which has a command syntax like ed
man  Display a particular manual entry
manweb  Manweb is part of the Netpbm package
mdu  Display the amount of space occupied by an MSDOS directory
mkdir  Create a directory
mkfs  Make a filesystem on a drive
mknod  Make block or character special files
mktemp  Make temporary filename (unique)
more  Page through text one screenful at a time.
mount  Mount a filesystem/device
mt  Control magnetic tape drive operation
mv  Move and / or rename files
:


 
  N
namei  Follow a pathname until a terminal point is found
nano  An enhanced free Pico clone
nc  arbitrary TCP and UDP connections and listens
(note that nc is also called the client interface
to the NEdit program but it is not the
command that invokes nedit-nc on current systems)
ncftp  Browser program for the File Transfer Protocol
nedit-nc  nedit-nc is the client interface to the NEdit text editor
netstat  Display verbose info about network processes and ports
nice  Run a command with modified priority
nisdomainname  Show or set system's NIS/YP domain name
nslookup  query internet domain name servers


P
paste  Merge lines of files
pdf2dsc  Generate a PostScript page list of a PDF document
pdf2ps  Convert PDF file "input.pdf" to PostScript(tm) in "output.ps"
pdfinfo  Print contents of the 'Info' dictionary (plus some other useful information) from a PDF file
pdftotext  Convert pdf files to plain text
perl  (start) Practical Extraction and Report Language
pgawk  The profiling version of gawk
pico  Text editor that comes with Pine (from the University of Washington)
pine  Email program used by The University of Washington
ping6  Ping
ping  Send ICMP ECHO_REQUEST to network hosts
pinky  A lightweight 'finger' program;
pr  Format for printing
ps  Processes running
ps2ascii  Ghostscript translator from PostScript or PDF to ASCII
ps2epsi  Generate conforming Encapsulated PostScript
ps2frag  Obsolete shell script for the PSfrag system
ps2pdf12  Convert PostScript to PDF 1.2 (Acrobat 3 and later compatible) using ghostscript
ps2pdf13  Convert PostScript to PDF 1.3 (Acrobat 4 and later compatible) using ghostscript
ps2pdf14  Use ps2pdfwr: Convert PostScript to PDF without specifying Compatibility Level, using ghostscript
ps2pdf  Convert PostScript to PDF using ghostscript
ps2pdfwr  Convert PostScript to PDF without specifying Compatibility Level, using ghostscript
ps2pk  creates a TeX pkfont from a type1 PostScript font
ps2ps  ps2ps uses gs to convert PostScript(tm) file "input.ps" to simpler and (usually) faster PostScript in "output.ps"
psbook  Rearranges pages from a PostScript document into "signatures" for printing books or booklets
pwd  Print Working Directory


Q  back to commands top
quota  display disk usage and limits


R  back to commands top
resize  Xterm window size
readelf  Displays information about ELF files
reboot  Stop the system, poweroff, reboot
red   red is a restricted ed: it can only edit files in the current directory and cannot execute shell commands
rename  Rename files
rmdir  Remove a directory
rm  Remove files or directories
rpm  rpm command options
rundig  Sample script to create a search database for ht://Dig
rview  The GUI version of Vim in easy mode with restrictions
rvi  Vi / Vim editor


S  back to commands top
sed  Stream editor
setfont  Load EGA/VGA console screen font
setgid  Set group id
setserial  Get / set Linux serial port info
setuid  Set user id
sfdisk  Modified fdisk program
sftp  Secure file transfer protocol (ftp)
sh  Shell (BASH)
shred  Safely remove data from disk drive
sleep  Delay for a specified amount of time
slocate  Security Enhanced version of the GNU Locate
sort  Sort lines of a text file
ssh  Secure shell connection command
stty  change and print terminal line settings
stty raw  Unformatted output to terminal
su  Become super user ( root )
switchdesk  Graphical and text mode interface for choosing desktop environment
sync  Force changed blocks to disk, update the super block
ssh  Secure shell connection command


T  back to commands top
tail  Print the last 10 Lines of a file standard output
tar  Create an Archive
tcsh  Enhanced completely compatible version of the Berkeley UNIX C shell, csh
tee  Copy standard input to each file, and also to standard output
telnet  User interface to the telnet protocol
time  Run the specified program command with the given arguments
touch  Change file timestamps
tracepath6  See tracepath
tracepath  Trace path to a network host discovering MTU along this path
traceroute6  See traceroute
traceroute  Print the route packets take to network host
tree  Display file tree
true  Exit with a status code indicating success
tty  Print name of terminal connected to standard output


U  back to commands top
umask  File creation mask / Bash builtins
umount  Detache file system(s) mentioned from file hierarchy
uname  Print system information ( kernel version )
unicode_start  Put keyboard and console into Unicode (UTF-8) mode
unicode_stop  Undo the effect of unicode_start
unlink  Call the unlink function to remove the specified file
uniq  Remove duplicate lines from sorted file
updatedb  Update the slocate database
unset gid  Group id change
unset uid  User id change
untar  Unarchive ( untar ) a file
unzip  Unzip .zip files
useradd  Add new user
users  Output who is currently logged in according to system records
usleep  Sleep a given number of microseconds. default is 1


V  back to commands top
view  Start vim in read-only mode
vi  Start the vi editor


W  back to commands top
w  Show who is logged on and what they are doing
wc  Word count of a file
wget  Non-interactive download of files from the Web
whatis  Search the whatis database for complete words (command names)
whereis  Locate a command or file
which  Find command path
whoami  Print effective userid
who  show who is logged on
whois  Client for the whois service


X,Y,Z  back to commands top
xinit  Start Xserver
xpdf  Portable Document Format (PDF) file viewer for X windows
xrandr  Change resolution running Xwindows ( command line )
ypdomainname  show or set the system's NIS/YP domain name
zcat  Compress or expand files
zip  Compression and file packaging utility for Unix, VMS, MSDOS, OS/2, Windows NT, Minix,
Atari and Macintosh, Amiga and Acorn RISC OS. It is analogous to a
combination of the UNIX commands tar(1) and compress(1) and is
compatible with PKZIP (Phil Katz’s ZIP for MSDOS
systems)

zipinfo  List detailed information about a ZIP archive


* All the above commands except the eject command ran on kernel 2.6.9-1.667 ( Fedora Core 3 ). I am still in the process of testing the recently added commands on older kernels.


  back to commands   back to beginning


Copyright (c) 2002 David Tarsi.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being no invariant sections, with the Front-Cover Texts being no Front-Cover Texts, and with the Back-Cover Texts being no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
GNU Free Documentation License


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