Linux-command-list

An Alphabetical List of Linux Commands

A

Anacron

Similar to Cron, this command runs commands periodically, with a frequency

specified in days

apt

short for Advanced Package Tool this utulity is used to manage software

packages popular in debian distros. This package uses several front ends such as

aptitude, apt-get, and symantec

aptitude

This is part of the Apt package. Used to manage software.

arp

Arp is a networking command. Used to display or manipulate the Linux Kernel's

IPv4 network neighbour cache. e.g. it relates IP adresses to Mac addresses.

at

Executes commands at a specified time.

atd

runs jobs queued by at

atq

Lists users pending jobs, if the user is the superuser everybodies job's are

listed.

atrm

deletes jobs using a job number to specify the job

B

bash

bash is the standard linux shell for almost all popular distros. The shell

interprets all other commands.

batch

executes commands when load levels permit as specified atd

bzip

A file compression utility, like gzip, but with better compression

C

cat

Short for concatenate this program reads files and prints to standard output.

cfdisk

A hard drive partitioning tool.

chage

this command allows you to change information related to user passwords. i.e.

when a password will expire.

chattr

modifies file permissions in a way similar to chmod.

chkconfig

manages which services will run in a specified runlevel

chmod

changes the permissions for one or more files.

chown

changes the ownership of one or more files both for the user and or the group.

chpasswd

changes the password for a user.

chroot

changes the root directory for a program, or for the users shell

cksum

Runs a CRC checksum for all specified files. Used to verify that a file was not

altered or corrupted during transfer.

clear

has the same effect as pressing ctrl and L. This clears your terminal of all

output.

cp

This command is used to copy files or directories to another locations.

cpio

this is an archiving tool similar to tar. intended to copy archive files to

tape, or disk.

crond

Executes commands at scheduled times as controlled by crontab

crontab

at it's most basic level, crontab allows you to edit your crontab file. This is

the file that controls what commands are set to run at a specific time.

cupsd

starts the print scheduler.

cut

allows you to cut information out from the specified files.

cvs

short for concurrent versions system allows multiple users to change, and

implement their changes to files concurrently.

D

date

Prints the current date and time, this can also be used by administrators to

change the date and time of the clock. See also hwclock.

dd

short for data dump this command makes a bit for bit copy of a specified

location. Though it can be a very powerful tool, this would not be used for

standard backup, or data manipulation.

df

Gives the available disk space of all mounted partitions, or on a specified

mounted partition.

diff

Used to show the differences between two files.

dig

Used to lookup DNS servers similar to the deprecated nslookup command.

dir

The same command as ls, even taking the same arguments. This command may not

necessarily be part of your distro, but exists for simplicity of people familiar

with Microsoft command line.

disable

disables access to a printer.

dmesg

a powerful troubleshooting command, this command displays the messages from the

kernel ring buffer meaning the information that flys by while your system is 

booting.

domainname

used to view or set the computers domain name.

doexec

executes the specified command with defined options, and arguments.

du

prints current disk usage for the specified location.

dosfsck

similar to fsck, but used for dos filesystems. This command attempts to

diagnose, and fix common filesystem errors.

dump

this is a backup utility available for specific linux filesystems that can

perform incremental backups after an initial full backup.

E

e2fsck

similar to fsck or dosfsck, this command is used to diagnose and attempt repairs

to a file system. Used for ext2 and ext3 systems.

echo

prints input as standard output. Also can be used to view environmental

variables.

edquota

allows you to edit filesystem quotas.

egrep

searches for lines that contain an extended regular expression.

enable

enables printers.

env

displays all environment variables this command can also be uses to change

environment variables .

expand

Converts tabs in files to defined number of spaces.

F

factor

displays the prime number of specified number.

false

This command returns an unsuccesful status. Peticularily useful in scripts.

fdisk

used to view, and edit partitions, and to change active partitions.

fetchmail

gets email from mailservers, and forwards it to the local system

fgrep

a variant of the grep command, this command searches for information that

matches the user defined input. This command is faster than grep, but may not be

as powerful.

file

gives information about the type of data the specified file contains.

find

A search utility for linux that can search by a number of different types of

data. e.g. name, type, or size.

finger

gives information about specified users

fmt

a command that can help unify formatting of text.

fold

breaks the lines of a file. ie. you can format a text file to only be a set

number of characters, bytes, or columns.

free

gives information about current RAM, and swap space usage.

fsck

checks and repairs damaged filesystems.

G

gpasswd

changes specified group password.

gpg

Stands for Gnu Privacy Guard. This command allows encryption and decryption of

data.

grep

This utility can be used to search for text within a file. When piped with

other commands it is very powerful.

groupadd

Creates new groups

groupdel

deletes groups from the system

groupmod

Modifies group information

groups

Shows the groups to which a user belongs

gs

Stands for GhostScript. This command is used to interpret Adobe's PostScript

and PDF filetypes.

gunzip

Used to unzip files compressed with gzip

gzexe

used to compress executable files.

gzip

used to compress files.

H

halt

Turns of the computer.

head

Prints the first several lines of specified files.

host

Gives information about hosts, or zones contained in DNS

hostname

sets or displays the current name of the host system.

hwclock

views or changes the hardware clock. See also date command.

I

iconv

converts files to a different character encoding

id

displays information about specified user

ifconfig

view, assigns or configures network interfaces and their addresses along with

other information.

inetd

A linux superserver for internet services.

info

an interactive screen which can give information about many linux commands,

directories, and other valuable linux information.

init

Command used to initialize the system, and change runlevels.

insmod

loads the specified file into the kernel. Not as robust as modprobe.

iptables

can be used to specify IP rules, and potentially build a firewall.

J

join

joins information in files to matching fields such as a line number.

K

kernelversion

gives information about the kernel you are using

kill

terminates process ids or PIDs

Killall

kills all processes related to specified command name.

klogd

allows you to specifiy what kernel messages are displayed, and prioritize them.

L

last

Displays a list of the most recent logins.

lastlog

display the last login times for system accounts

less

pages files or output, is much more robust than the more command. less is more.

lftp

A file transfer program that can use ftp, http, ftps, and https protocols.

ln

Creates hard or soft links to files.

locale

Displays current locale settings.

locate

searches a database of file names. database is updated by updatedb command.

logger

Adds information to the system log.

login

Logs into the system

logrotate

used to rotate, and otherwise manipulate log files.

lpq

checks for the status of print jobs.

lpr

sends files to be printed.

lprm

allows for the cancelling of print jobs.

ls

lists the specified directory.

lspci

lists attached PCI devices

lsof

Lists open files and information about the open files.

lsmod

Lists loaded modules.

lsusb

lists USB devices.

M

mail

a command used for reading and sending mail to other users.

mailq

shows messages currently in the mail queue

man

shows the help manual for specified command

mkdir

creates directories.

modinfo

gives information about the specified module

modprobe

attempts to load a module, as well as all modules original module depends on.

more

pages files or other input

mount

tries to mount the specified drive.

mv

Used to move, or rename files or directories.

N

netstat

a command used to give information on active ports, and other network

information

newgrp

changes users default group.

nice

allows for the priority of a command to be raised or lowered

nslookup

looks up domain nameservers. Has been replaced with dig and host commands.

P

passwd

allows the creation or changin of a password associated with a user

paste

merges lines of files into tab-separated columns

pidof

Show the process IDs of the requested program

ping

used to test network connectivity. displays basic information on requested ip

address, and response times.

pr

prepares a text file for a printer friendly format.

ps

shows information about running processes.

pwd

Prints the entire path of the current working directory.

Q

quota

displays information on specified user and group disk quotas.

quotacheck

checks and corrects disk quota information. Usually ran at startup

quotaon

turns on the disk quota requirements.

quotaoff

turns of the disk quota requirements.

quotastats

displays disk quota information

R

reboot

reboots the system.

reject

tells printing system to reject specified destinations

renice

changes the priority of already running processes

repquota

creates a report for diskusage and quotas on the specified disk.

reset

essentially the same as hitting the reset button, but this command is limited

to the terminal

restore

restores backup files from a dump. See also dump.

rm

deletes files, and if passed the correct option, directories also.

rmdir

deletes directories, but not not the files they might contain.

rmmod

uninstalls modules from the kernel, generally you would want to use modprobe

instead.

route

allows the addition or deletion of entries in the routing tables.

rpm

the red hat package manager. Used to install, upgrade, and uninstall packages.

rsync

used to transfer files, typically accross a newtork.

runlevel

displays runlevel information

S

scp

used to securely transfer files.

sed

Sed is a stream editor used to make basic changes to an input stream.

seq

this command is used to print one incremental number per line to standard

output.

setquota

used to set a diskquota

sftp

a secure file trasfer protocol that can be used via command line.

sh

the standard unix shell.

shred

securely overwrites, and deletes files.

shutdown

used to shutdown the computer. Can be set to shutdown in a certain amount of

time, or at a certain time.

size

shows the six of a file

sleep

defines a period of time the computer shou wait before processing another

command

ssh

Used to logon securely to another server, and run commands.

ssh-add

Adds identities the the authentication agent.

ssh-agent

Used to hold private key for use with public key authentication

ssh-keygen

Used to generate and manage authentication keys for SSH.

ssh-keyscan

uses to gather public and private keys from other hosts.

stat

displays file or system status

su

Switches User, if no user is given attempts to become superuser.

sudo

Gives access to execute command as another user

sum

creates a checksum for the specified file

swapoff

disables devices for swapping

swapon

enables devices for swapping

T

tail

Displays the last 10 lines of requested files

talk

a basic chat program

tar

This command stands for tape archiving. It is used to copy or restore files from

tape or disk

tcpd

command to monitor incoming requests for specific services

tcpdump

this command allows you to dump tcpip information to a medium to be examined.

telnet

allows logging into another system remotely, and executing commands

tftp

allows users to transfer files to and from remote machines.

top

top provides information about the most cpu intensive processes running.

touch

creates files, and or can update access and modification times of a file.

tr

stands for translates character, and does just that, translating the characters

you specify into another set of characters you specify.

tracepath

traces the path to the specified host. Not as robust as traceroute

traceroute

traces path to specified host.

true

a command that returns a successful status.

U

umount

unmount the specified filesystem

uname

displays information about the machine and operating system

uptime

prints information about the current sessions.

useradd

creates new user accounts.

userdel

deletes specified ser accounts

usermod

allows for modification of user accounts.

V

vi

a text editor

vmstat

gives information on virtual memory

W

w

gives information on currently logged in users, and their activities.

warnquota

used to set the why and who of to email when a user reaches their soft quota

limit.

wget

used for basic file downloading over the web

whatis

A way to search for linux commands from the command prompts.

whereis

locates the source and manual pages for linux commands and files.

which

lists the pathnames of the files that would be executed if the specified

command had been run.

who

shows who is logged into the system

whois

searches whois for information on a domain name, or IP

write

a way to initiate or respond to an interactive conversation with another user

X

xargs

builds and execute command lines from standard input.

xinetd

A linux Superserver that listens to tcpip requests on behalf of other programs.

Y

yes

repeatedly outputs a line with specified strings, or just a y if unspecified.

Used mostly in scripts.