The following list describes some of the most useful
and popular Linux commands. Consult the man page for each command to learn
about additional arguments and details of operation.
-
adduser userid
Creates a new userid, prompting for necessary information
(requires root privileges).
-
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
Prints 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
Prints a calendar for the specified month of the specified
year.
-
cat files
Prints 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. Similar
to the diff command, though the output format differs.
-
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
Prints 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
Prints the messages resulting from the most recent system
boot.
-
du
-
du directories
Prints the amount of disk space used by the current directory
(or the specified directories) and its (their) subdirectories.
-
echo string
-
echo -n string
Prints 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
-
fq 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
Prints 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
Search the specified files for text matching the specified
pattern (usually enclosed in single quotes) and print 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 file name and line number. The -v option reverses
the matching, causing non-matched lines to be printed.
-
gzip files
-
gunzip files
Compress (or expand) the specified files. Generally, a compressed
file has the same name as the original file, followed by . gz.
-
head files
Prints 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 run_level
Changes the system run level to the specified value (requires
root
privileges).
-
insmod module
Dynamically loads the specified module (requires root
privileges).
-
jobs
Displays all background jobs.
-
ispell files
Checks the spelling of the contents of the specified files.
-
kill process_ids
-
kill -signal process_ids
-
kill -l
Kills the specified processes, sends the specified processes
the specified signal (given as a number or name), or prints a list of available
signals.
-
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.
-
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
Prints the entries of the print queue.
-
lpr files
Prints 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 (non-hidden) files in the current directory or the specified
files or directories. The -a option lists hidden files as well has
non-hidden 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
Prints the specified man page.
-
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 file system of the specified type (such as
ext2
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
Space
key 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
Prints 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, ext2, msdos,
or iso9660, the filesystem type generally used for CD-ROMs).
-
mv paths target
Moves the specified files or directories to the specified target.
-
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 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
Prints 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 -i files
-
rm -f 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 -i option causes the command to prompt for
confirmation; the -f option suppresses 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.
-
shutdown 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.
-
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.
-
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.
-
swapon device
Enables use of the specified device for swapping (requires
root
privileges).
-
swapoff device
Disables use of the specified device for swapping (requires
root
privileges).
-
sync
Completes all pending input/output operations (requires
root
privileges).
-
tail file
-
tail -n file
-
tail -f file
Prints the last several lines of the specified files. The -n
option specifies the number of lines to be printed. The -f option
causes the command to continuously print additional lines as they are written
to the file.
-
talk user
Launches a program that allows a chat-like 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 specified
that the tar file will be compressed.
-
tar xvf tar_file
-
tar zxvf tar_file
Extracts the contents of the specified tar file. The
z
option specified that the tar file has been compressed.
-
telnet host
Opens a login session on the specified host.
-
top
Prints a display of system processes that's continually updated
until the user presses the q key.
-
traceroute host
Uses echo requests to determine and print a network path to
the host.
-
umount device
Unmounts the specified filesystem (generally requires
root
privileges).
-
uptime
Prints the system uptime.
-
w
Prints the current system users.
-
wall
Prints a message to each user except those who've disabled
message reception. Type Ctrl-D to end the message.
-
wc files
Prints the number of characters, words, and lines in the specified
files.