Linux Commands

Linux Commands
Documentations

man - Format and display the on-line manual pages

help - Display help info about Bash builtin commands

info - Read/display Info documents

manpath - Determine user’s search path for man pages

apropos - Search the whatis database for strings

whatis - Search the whatis database for complete words

Command/File Information

which - Shows the full path of a (shell) command

whereis - Locate the binary, source, and manual page files for a command

locate, slocate - Find file paths containing string using slocate database

find - Search for files in a directory hierarchy

type - Show if command is alias, etc.

file - Determine type of file

File Operations

cat - Concatenate files and print on the standard output

tac - Concatenate and print files in reverse

more, less - Output file page by page

tail - Output the last part of files

head - Output the first part of files

rm - Remove files (or directories)

mv - Move (rename) files

cp - Copy files and directories

dd - Convert and copy a file

grep, egrep, fgrep - Print lines matching a pattern

ln - Make a hard/soft link to a file

od - Dump files in octal and other formats

source - Read and execute commands in a file [Bash builtin]

File Properties

chmod - Change file access permissions

chown - Change file owner (and group)

chgrp - Change group ownership

stat - Display file or filesystem status

touch - Change file timestamps (or create empty file)

wc - Print the number of newlines, words, and bytes in files

Directories

ls - List directory contents

pwd - Print name of current working directory

cd - Change directory

mkdir - Make directories

rmdir - Remove empty directories

du - Estimate file space usage

pushd - cd and add directory to the directory stack [Bash builtin]

popd - Remove directory from directory stack and cd [Bash builtin]

dirs - Display the currently remembered directories [Bash builtin]

File Comparison

diff - Compare 2 files line by line

cmp - Compare 2 files byte by byte

comm - Compare sorted files by line

diff3 - Compare 3 files line by line

sdiff - Merge 2 files side-by-side

patch - apply a diff file to an original

Environment Variables, Aliases, and Functions

printenv - Print (select or all) environment variable values

export - Move shell variable to environment (so inherited by children) [Bash builtin]

set - Print values of all shell/environment variables and functions

unset - Remove/undefine a variable [Bash builtin]

declare - Show (or set) shell variables/functions [Bash builtin]

env - Run a program in a modified environment

setenv, unsetenv - Set/remove environment variable value [C shell]

alias - Show (or set) alias value for command

unalias - Remove/unset alias

System Information

hostname - Show or set the system’s host name

uname - Print system (kernel, etc.) information

uptime - Tell how long the system has been running

free - Display amount of free and used memory in the system

vmstat - Report virtual memory statistics

dmesg - Print or control the kernel ring buffer (e.g., boot messages)

id - Print UID and GID info for current user or specified username

last, lastb - Display list of recent logins/failed logins

finger - Display information about system users (often disable now)

who - Show who is logged in (often disabled now)

Processes

ps - Snapshot of the current processes

pstree - Display a tree of processes

top - Display current processes (realtime)

kill - Terminate a process (send a signal)

fuser, lsof - Identify processes using files or sockets

id - Print UID and GID info for current process

nice - Run a program with modified scheduling priority

renice - Alter priority of running process(es)

umask - Set process’ file creation permissions mask [Bash builtin]

ulimit - Control process resources limits [Bash builtin]

Filesystems/devices

df - Report filesystem disk space usage

mount - Mount a filesystem

umount - Unmount filesystem

fdisk, cfdisk, sfdik- Manipulate disk partition table

mkfs - Build a Linux file system

fsck- Check and repair a Linux file system

debugfs - Ext2/ext3 file system debugger

mkswap - Set up a Linux swap area

swapon, swapoff - Enable/disable devices and files for swapping

mknod - Make block or character special files

dd - Convert and copy a file

Archiving and Compression

tar - Package/unpackage files (archive)

gzip, gunzip - Compress or expand files

zip, unzip - Package and compress (archive) files

bzip2, bunzip2 - Compress or expand files

bzcat - decompresses files to stdout

compress, uncompress - Compress or expand files (old)

cpio - Copy files to and from archives

Filters

basename - Strip directory and suffix

cat - Concatenate and write files

csplit - Split by context

cut - Print selected parts of lines

dirname - Strip non-directory suffix

envsubst - Convert shell vars to environment values

expand - Convert tabs to spaces

fmt - Reformat paragraph text

fold - Wrap long input lines

grep, egrep, fgrep - Print lines matching a pattern

head - Output the first part of files

join - Join lines on a common field

nl - Number lines and write files

paste - Merge lines of files

pr - Paginate or columnate files

sed - Stream editor

seq - Print a sequence/list of numbers

sort - Sort text files

split - Split into fixed-size pieces

tac - Reverse files

tail - Output the last part of files

tee - Redirect to multiple files

tr - Translate characters

tsort - Topological sort

unexpand - Convert spaces to tabs

uniq - Uniquify files

wc - Print the number of newlines, words, and bytes in files

xargs - Convert standard input to command argument(s)

Login, Shell/Command, Logout

su - Run as a substitute user (e.g., root)

sudo - Execute a command as another user (e.g., root)

exit - Exit a shell

logout - Logout/exit a login shell (e.g., SSH shell)

chroot - Run command or interactive shell with special root directory

Login, Shell/Command, Logout

ssh - Secure remote login/shell

sftp - Secure file transfer program

scp - Secure remote file copy

rsh - Remote login/shell (insecure!)

rlogin - Remote login (insecure!)

ftp - File transfer program (insecure!)

rcp - Remote file copy (insecure!)

Users

passwd - Update a user’s password

chsh - Change your login shell

useradd - Create a new user or update default new user information

userdel - Delete a user account and related files

usermod - Modify a user account

groupadd - Create a new group

groupdel - Delete a group

groupmod - Modify a group

Printing and Formatting

lpr - Print files

lpq - Show printer queue status

lprm - Cancel print jobs

lpstat - Print cups status information

enscript - Convert text files to PostScript for printing, etc.

a2ps - Format files for printing on a PostScript printer

mpage - print multiple pages per sheet on PostScript printer

Booting, Startup/Runlevel, Shutdown

lilo - Install LILO boot loader

grub - Run the GRUB (boot loader) shell

init, telinit - Change system runlevel

halt, reboot, poweroff - Stop the system

shutdown - Bring the system down

mkrescue - Make rescue floppy (to boot disk from floppy/cd)

Services

service - Start/stop/restart/status a system service/daemon

chkconfig - Update/query runlevel information for system services

Network

ping, ping6 - Send ICMP ECHO_REQUEST to network hosts

traceroute - Print the route packets take to network host

ifconfig - Configure a network interface

ifup, ifdown - Start/stop a network interface

ethtool - Display or change ethernet card settings

route - Show/manipulate the IP routing table

netstat - Print network connections, routing tables, etc.

host, dig, nslookup - DNS lookup utilities

whois - Client for the whois directory service (DNS)

iptables - Administration tool for IPv4 packet filtering and NAT

arp - Manipulate the system ARP cache

arping - Send ARP REQUEST to a neighbour host

Terminal

stty - Change and print terminal line settings

reset, tset - Terminal initialization

clear - Clear the terminal screen

screen - Terminal manager/multiplexer (multiple shells on a console)

Job Control

jobs - List jobs (running in background)

fg - Move job to foreground

bg - Move job to background

Kernel Modules and Configuration

lsmod - Show the status of Linux kernel modules

modprobe - Add and remove modules from the Linux kernel

insmod - Insert a module into the Linux kernel

rmmod - Remove a module from the Linux kernel

modinfo - Show information about a Linux kernel module

mkinitrd - Creates initial ramdisk images for preloading modules

sysctl - Configure kernel parameters at runtime

Hardware

hdparm - Get/set hard disk parameters

lshw - List hardware

lspci - List all PCI devices

lsscsi - List all SCSI devices

lsusb - List USB devices

usbview - Display information on USB devices

usbmodules - List kernel driver modules available for a USB device

Time

date - Print or set the system date and time

hwclock - Query and set the hardware clock (RTC)

ntpdate - Set the system date and time via NTP

File Integrrity Checking

md5sum - Compute and check MD5 message digest (checksum)

sha1sum - Compute and check SHA1 message digest (checksum)

Compiling and Libraries

gcc - Gnu Compiler Collection (C/C++ and more compiler)

./configure - Standard command to use autoconf script to create makefile(s)

make - Build program(s) from source (invoking compiler)

ldconfig - Update link bindings info for shared libraries

ldd - Print shared library dependencies for an executable

RPM Software Package Management

rpm - basic RPM package command

urpmi - Mandriva RPM package command (understands dependencies)

urpmi.addmedia, urpme, urpmf, urpmq - various urpmi-related commands

rpmdrake - Mandriva GUI front end for urpmi

yum - RH/Fedora RPM package command (understands dependencies)

yumex - RH/Fedora GUI front end for yum

Debian Software Package Management

dpkg - basic Debian package command

apt-get - Command line front end for APT (understands dependencies)

aptitude - Advanced text and command line front end for APT

synaptic - GUI front end for APT

dselect - Menu-driven package manager

Misc

watch - Execute a program periodically, showing output fullscreen

true, false - Do nothing, successfully, unsuccessfully

mail, nail - Send and receive mail (command line)