The following list describes some of the most useful and popular
Linux commands. Consult the manpage for each command to learn about
additional arguments and details of operation.
- adduser userid
-
Creates a
new userid, prompting for necessary information
(requires root privs).
- alias name='command'
-
Defines name as an alias for the
specified command.
- apropos keyword
-
Searches the
manual pages for occurrences of the specified keyword and prints
short descriptions from the beginning of matching manual pages.
- at time
- at -f file time
-
Executes commands entered via
STDIN (or by using the alternative form, the specified file) at the
specified time. The time can be specified in a variety of ways; for
example, in hour and minute format (hh:mm) or in
hour, minute, month, day, and year format (hh:mm
mm/dd/yy).
- atq
-
Displays descriptions of jobs pending
via the at command.
- atrm job
-
Cancels
execution of a job scheduled via the at command. Use the atq command to discover the identities of
scheduled jobs.
- bg
- bg jobs
-
Places the current job
(or by using the alternative form, the specified jobs) in the
background, suspending its execution so that a new user prompt
appears immediately. Use the jobs
command to discover the identities of background jobs.
- cal month year
-
Displays
a calendar for the specified month of the specified year.
- cat files
-
Displays the contents of the specified
files.
- cd
- cd directory
-
Changes the current working
directory to the user's home directory or the
specified directory.
- chgrp group files
- chgrp -R group files
-
Changes
the group of the specified files to the specified group. The
alternative form of the command operates recursively, changing the
group of subdirectories and files beneath a specified directory. The
group must be named in the /etc/groups file,
maintained by the newgroup command.
- chmod mode files
- chmod -R mode files
-
Changes
the access mode of the specified files to the specified mode. The
alternative form of the command operates recursively, changing the
mode of subdirectories and files beneath a specified directory.
- chown userid files
- chown -R userid files
-
Changes the owner of the specified files to
the specified userid. The alternative form of
the command operates recursively, changing the owner of
subdirectories and files beneath a specified directory
- clear
-
Clears the
terminal screen.
- cmp file1 file2
-
Compares
two files, reporting all discrepancies. Unlike the diff command, cmp can compare multiple files and binary
files.
- cp file1 file2
- cp files directory
- cp -R files directory
-
Copies
a file to another file or directory or copies a subdirectory and all
its files to another directory.date
- date date
-
Displays
the current date and time or changes the system date and time to the
specified value, of the form MMddhhmmyy or
MMddhhmmyyyy.
- df
-
Displays the amount of free
disk space on each mounted filesystem.
- diff file1 file2
-
Compares
two files, reporting all discrepancies. Similar to the cmp command, though the output format differs.
- dmesg
-
Displays the messages resulting
from the most recent system boot.
- du
- du directories
-
Displays the amount of disk space
used by the current directory (or the specified directories) and its
(their) subdirectories.
- echo string
- echo -n string
-
Displays the
specified text on the standard output stream. The -n option causes omission of the trailing
newline character.
- fdformat device
-
Formats the media inserted in the
specified floppy disk drive. The command performs a low-level format
only; it does not create a filesystem. To create a filesystem, issue
the mkfs command after formatting
the media.
- fdisk device
-
Edits the partition table of the
specified hard disk.
- fg
- fg jobs
-
Brings the current job (or the
specified jobs) to the foreground.
- file files
-
Determines and prints a description
of the type of each specified file.
- find path -name pattern -print
-
Searches the specified path for files with
names matching the specified pattern (usually enclosed in single
quotes) and prints their names. The find command has many other
arguments and functions; see the online documentation.
- finger users
-
Displays descriptions of the
specified users.
- free
-
Displays the amount of used and free system
memory.
- ftp hostname
-
Opens an FTP connection to the specified
host, allowing files to be transferred. The FTP program provides
subcommands for accomplishing file transfers; see the online
documentation.
- grep pattern files
- grep -i pattern files
- grep -n pattern files
- grep -v pattern files
-
Searches the specified files for text
matching the specified pattern (usually enclosed in single quotes)
and prints matching lines. The -i
option specifies that matching is performed without regard to case.
The -n option specifies that each
line of output is preceded by the filename and line number. The
-v option reverses the matching,
causing nonmatched lines to be printed.
- gzip files
- gunzip files
-
Expands
or compresses the specified files. Generally, a compressed file has
the same name as the original file, followed by
.gz.
- head files
-
Displays the first several
lines of each specified file.
- hostname
- hostname name
-
Displays
(or sets) the name of the host.
- info
-
Launches the GNU Texinfo help system.
- init runlevel
-
Changes
the system runlevel to the specified value (requires
root privileges).
- insmod module
-
Dynamically loads the specified
module (requires root privileges).
- ispell files
-
Checks the spelling of the contents
of the specified files.
- jobs
-
Displays all background jobs.
- kill process_ids
- kill -l
- kill -signal process_ids
-
Kills
the specified processes, prints a list of available signals, or sends
the specified processes the specified signal (given as a number or
name).
- killall program
- killall -signal program
-
Kills
all processes that are instances of the specified program or sends
the specified signal to all processes that are instances of the
specified program.
- less file
-
Lets the user peruse a file too large to be
displayed as a single screen (page) of output. The less command, which is more powerful than the
more command, provides many
subcommands that let the user navigate the file. For example, the
spacebar moves forward one page, the b key moves back one page, and the q key exits the program.
- links URL
-
Views the
specified web page.
- ln old new
- ln -s old new
-
Creates
a hard (or soft) link associating a new name with an existing file or
directory.
- locate pattern
-
Locates files with names containing the
specified pattern. Uses the database maintained by the updatedb command.
- lpq
-
Displays
the entries of the print queue.
- lpr files
-
Displays the
specified files.
- lprm job
-
Cancels printing of the specified print
queue entries. Use lpq to determine
the contents of the print queue.
- ls
- ls files
- ls -a files
- ls -l files
- ls -lR files
-
Lists
(nonhidden) files in the current directory or the specified files or
directories. The -a option lists
hidden files as well as nonhidden files. The -l option causes the list to include
descriptive information, such as file size and modification date. The
-R option recursively lists the
subdirectories of the specified directories.
- mail
-
Launches a
simple mail client that permits sending and receiving email messages.
- man title
- man section title
-
Displays the
specified manpage.
- mkdir directories
- mkdir -p directories
-
Creates
the specified directories. The -p
option causes creation of any parent directories needed to create a
specified directory.
- mkfs -t type device
-
Creates
a filesystem of the specified type (such as ext3
or msdos) on the specified
device (requires root
privileges).
- mkswap device
-
Creates a Linux swap space on the specified
hard disk partition (requires root privileges).
- more file
-
Lets the user peruse a file too large to be
displayed as a single screen (page) of output. The more command provides many subcommands that
let the user navigate the file. For example, the spacebar moves
forward one page, the b key moves
back one page, and the q key exits
the program.
- mount
- mount device directory
- mount -o option -t type device directory
-
Displays the mounted devices or mounts
the specified device at the specified mount point (generally a
subdirectory of /mnt). The mount command
consults /etc/fstab to determine standard
options associated with a device. The command generally requires
root privileges. The -o option allows specification of a variety of
options, for example, ro for
read-only access. The -t option
allows specification of the filesystem type (for example,
ext3, msdos, or
iso9660, the filesystem type generally used for
CD-ROMs).
- mv paths target
-
Moves
the specified files or directories to the specified target.
- nano
- nano file
-
Launch nano to edit or create specified
file, if any.
- newgroup group
-
Creates
the specified group.
- passwd
- passwd user
-
Changes the current
user's password or that of the specified user
(requires root privileges). The command prompts
for the new password.
- ping -n ip_address
- ping host
-
Sends an echo
request via TCP/IP to the specified host. A response confirms that
the host is operational.
- pr files
-
Formats the specified files for
printing, by inserting page breaks and so on. The command provides
many arguments and functions.
- ps
- ps -aux
-
Displays
the processes associated with the current userid
or displays a description of each process.
- pwd
-
Displays the absolute path
corresponding to the current working directory.
- reboot
-
Reboots
the system (requires root privileges).
- reset
-
Clears
the terminal screen and resets the terminal status.
- rm files
- rm -f files
- rm -i files
- rm -if files
- rm -rf files
-
Deletes
the specified files or (when the -r
option is specified) recursively deletes all subdirectories of the
specified files and directories. The -f option suppresses confirmation; the
-i option causes the command to
prompt for confirmation. Because deleted files cannot generally be
recovered, the -f option should be
used only with extreme care, particularly when used by the
root user.
- rmdir directories
- rmdir -p directories
-
Deletes
the specified empty directories or (when the -p option is specified) the empty directories
along the specified path.
- scp host1:file host2:
-
Copies file
from host1 to host2, via
SSH.
- shutdown minutes
- shutdown -h minutes
- shutdown -r minutes
-
Shuts down
the system after the specified number of minutes elapses (requires
root privileges). The -r option causes the system to be rebooted once
it has shut down. If the -r option
is absent, the system is halted and powered off; the -h option also halts and shuts down the system.
Alternatively, now can be used
instead of minutes, which forces an immediate
reboot or halt of the system.
- sleep time
-
Causes the command interpreter to pause
for the specified number of seconds.
- sort files
-
Sorts
the specified files. The command has many useful arguments; see the
online documentation.
- split file
-
Splits
a file into several smaller files. The command has many arguments;
see the online documentation.
- ssh host -l userid
-
Logs in to host via
SSH, using the specified userid.
- su
- su user
- su -
- su - user
-
Changes the current
userid to root or to the
specified userid (the latter requires
root privileges). The - option establishes a default environment for
the new userid.
- swapoff device
-
Disables
use of the specified device for swapping (requires
root privileges).
- swapon device
-
Enables use
of the specified device for swapping (requires
root privileges).
- sync
-
Completes all
pending input/output operations (requires root
privileges).
- tail file
- tail -f file
- tail -n file
-
Displays the last several lines of
the specified files. The -f option
causes the command to continuously print additional lines as they are
written to the file. The -n option
specifies the number of lines to be printed.
- talk user
-
Launches a program that allows a chatlike
dialog with the specified user.
- tar cvf tar_file files
- tar zcvf tar_file files
-
Creates a tar
file with the specified name, containing the specified files and
their subdirectories. The z option
specifies that the tarfile will be compressed.
- tar xvf tar_file
- tar zxvf tar_file
-
Extracts the
contents of the specified tarfile. The z option specifies that the tarfile has been
compressed.
- telnet host
-
Opens a login session on the specified
host.
- time
-
Times the execution of a job.
- top
-
Displays
a display of system processes that's continually
updated until the user presses the q
key.
- touch file
-
Changes file
access time. If the specified file does not exist, the command
creates an empty (new) file.
- traceroute host
-
Uses echo
requests to determine and print a network path to the host.
- umask mask
-
Specifies default permissions
assigned to created directories and files.
- umount device
-
Unmounts
the specified filesystem (generally requires
root privileges).
- uname -a
-
Displays
information about the system.
- unzip file
-
Unzips
a compressed file.
- uptime
-
Displays the system uptime.
- w
-
Displays the current system users.
- wall
-
Displays a message to each user except
those who've disabled message reception. Type
Ctrl-D to end the message.
- wc files
-
Displays the number of
characters, words, and lines in the specified files.
- who
-
Displays
information about system users.
- zip file
-
Compresses
the specified file.