Command Description
– – – – – – – – – – – –
alias Create an alias
apropos Search manual for keyword
at Schedule a job to run in the future.
awk Find and Replace text within file(s)
break Exit from a loop
builtin Run a shell builtin
bunzip2 Decompress file from bzip2 format
bzip2 Compress file to bzip2 format
cal Display a calendar
case Conditionally perform a command
cat Concatenate files to standard output
cd Change Directory
cfdisk Partition table manipulator for Linux
chgrp Change group ownership
chmod Change access permissions
chown Change file owner and group
chroot Run a command with a different root directory
chvt Change the virtual Terminal
cksum Print CRC checksum and byte counts
clear Clear terminal screen
cmp Compare two files
comm Compare two sorted files line by line
command Run a command – ignoring shell functions
compress Compress file(s) to old Unix compress format
continue Resume the next iteration of a loop
convmv A perl script that converts filenames from one encoding to another
cp Copy one or more files to another location
cron Daemon to execute scheduled commands at predefined time
crontab Schedule a command to run at a later time
csplit Split a file into context-determined pieces
cut Divide a file into several parts
date Display or change the date & time
dc Desk Calculator
dd Data Dump – Convert and copy a file
declare Declare variables and give them attributes
df Display free disk space
diff Display the differences between two files
diff3 Show differences among three files
dir Briefly list directory contents
dircolors Colour setup for `ls’
dirname Convert a full pathname to just a path
dirs Display list of remembered directories
du Estimate file space usage
echo Display message on screen
ed A line-oriented text editor (edlin)
egrep Search file(s) for lines that match expression
eject Eject CD-ROM
enable Enable and disable builtin shell commands
env Disp, set, or remove environment variables
eval Evaluate several commands/arguments
exec Execute a command
exit Exit the shell
expand Convert tabs to spaces
export Set an environment variable
expr Evaluate expressions
factor Print prime factors
FALSE Do nothing, unsuccessfully
fdformat Low-level format a floppy disk
fdisk Partition table manipulator for Linux
fgrep Search file(s) for lines that match a fixed string
file Determine type of file
find Search for files that meet a desired criteria
fmt Reformat paragraph text
fold Wrap text to fit a specified width.
for Expand words, and execute commands
format Format disks or tapes
free Disp, s memory usage
fsck Filesystem consistency check and repair.
fstat List open files
function Define Function Macros
fuser Identify process using file
gawk Find and Replace text within file(s)
getopts Parse positional parameters
grep Search file(s) for lines that match a given pattern
groups Print group names a user is in
gunzip Decompress file(s) from GNU zip format
gzcat Show contents of compressed file(s)
gzip Compress file(s) to GNU zip format
hash Remember the full pathname of a name argument
head Output the first part of file(s)
history Command History
hostname Print or set system name
iconv Converts the encoding of characters from one code page to another.
id Print user and group id’s
if Conditionally perform a command
import Capture an X server screen and save the image to file
info Help info
install Copy files and set attributes
join Join lines on a common field
kill Stop a process from running
less Display output one screen at a time
let Perform arithmetic on shell variables
ln Make links between files
local Create variables
locate Find files
logname Print current login name
logout Exit a login shell
lpc Line printer control program
lpr Off line print
lprint Print a file
lprintd Abort a print job
lprintq List the print queue
lprm Remove jobs from the print queue
ls List information about file(s)
ll #ls -l List information about file(s)
lsof List open files
m4 Macro processor
makewhatis Rebuild whatis database
man Print manual pages
mkdir Create new folder(s)
mkfifo Make FIFOs (named pipes)
mknod Make block or character special files
more Display output one screen at a time
mount Mount a file system
mtools Manipulate MS-DOS files
mv Move or rename files or directories
netconfig Configure your network
nice Set the priority of a command or job
nl Number lines and write files
nohup Run a command immune to hangup
od View binary files
passwd Modify a user password
paste Merge lines of files
pathchk Check file name portability
popd Restore the previous value of the current directory
pr Convert text files for printing
printcap Printer capability database
printenv Print environment variables
printf Format and print data
ps Process status
pushd Save and then change the current directory
pwd Print Working Directory
quota Display disk usage and limits
quotacheck Scan a file system for disk usage
quotactl Set disk quotas
pax Archive file(s)
ram ram disk device
rcp Copy files between two machines.
read read a line from standard input
readonly Mark variables/functions as readonly
remsync Synchronize remote files via email
return Exit a shell function
rm Remove (delete) files
rmdir Remove folder(s)
rpm RPM Package Manager (was RedHat Package Manager)
rsync Remote file copy (Synchronize file trees)
screen Terminal window manager
sdiff Merge two files interactively
sed Stream Editor
select Accept keyboard input
seq Print numeric sequences
set Manipulate shell variables and functions
shift Shift positional parameters
shopt Shell Options
shutdown Shutdown or restart linux
sleep Delay for a specified time
sort Sort text files
source Run commands from a file `.’
split Split a file into fixed-size pieces
strings print the strings of printable characters in files.
su Substitute user identity
sum Print a checksum for a file
symlink Make a new name for a file
sync Synchronize data on disk with memory
tac Print files out in reverse line order
tail Output the last part of files
tar Tape ARchiver
tee Redirect output to multiple files
test Evaluate a conditional expression
time Measure Program Resource Use
times User and system times
timidity Play midi files and set up software.
touch Change file timestamps
top List processes running on the system
traceroute Trace Route to Host
trap Run a command when a signal is set(bourne)
tr Translate, squeeze, and/or delete characters
TRUE Do nothing, successfully
tsort Topological sort
tty Print filename of terminal on stdin
type Describe a command
ulimit Limit user resources
umask Users file creation mask
umount Unmount a filesystem
unalias Remove an alias
uname Print system information
unexpand Convert spaces to tabs
uniq Uniquify files (remove all duplicate lines)
units Convert units from one scale to another
unset Remove variable or function names
unshar Unpack shell archive scripts
until Execute commands (until error)
useradd Create new user account
usermod Modify user account
users List users currently logged in
uuencode Encode a binary file into 7-bit ASCII characters
uudecode Decode a file created by uuencode
v Verbosely list directory contents (`ls -l -b’)
vdir Verbosely list directory contents (`ls -l -b’)
watch Execute/display a program periodically
whatis List manual pages by name
wc Print byte, word, and line counts of a file
whereis Report all known instances of a command
which Locate a program file in the user’s path.
while Execute commands
who Print all usernames currently logged in
whoami Print the current user id and name (`id -un’)
xargs Execute utility, passing constructed argument list(s)
yes Print a string until interrupted
zcat Show contents of compressed file(s)
zip Compress and archive file(s) to zip format
.period Run commands from a file
### Comment / Remark
Tag: Centos commands
100+ Linux system admin commands cheat sheet
There are more than 1000’s of commands in Linux. But this the most important commands which a System Admin should known.
Are you ready to check your command Knowledge ?
1) date : Displays the current date. 2) cal : calender for any specific month or a complete year. 3) man : Displays the documentation for a command.. 4) echo : Print message on the terminal. 5) script : Records your session and stores it in a file. 6) useradd : Command used to create a new user 7) passwd : Command allows you to change your password 8) who : To get the logged in user information. 9) ll : To see the file attributes (long list). 10) mkdir : Command used to make a directory. 11) cd : Command for changing current directory. 12) touch : Command used to create a file. 13) cat : To display the contents of a small file on terminal. 14) mv : For renaming and to move a file/folder. 15) cp : Command used to copy a file or folder. 16) rm : Command used to remove a file. 17) rmdir : Command used for deleting folders. 18) pwd : Command used to know the present working directory. 19) chmod : Changing the permissions of the file. 20) setfacl : To set special Permission. 21) ls : Command used for listing the contents. 22) more/less : Used to view large files one page at a time. 23) wc : Command is used to count lines, 24) cmp : Compare two files whether they are identical or not. 25) comm : displays the common between both the files. 26) gzip : Command is used to compress the file. 27) gunzip : Command which is used to de-compress it. 28) tar : Command is used to create archive a group files. 29) head : Command displays the top of the file. 30) tail : Command displays the end of the file. 31) sort : To sort the file based on field by using -t and -k option. 32) grep : Scans its input for a pattern, display the selected pattern. 33) chown : Changing the ownership and also group of the file. 34) vim : Vi Improved, a programmers text editor. 35) find : Command used to search for files in a directory hierarchy. 36) history : Command which prints recently used commands. 37) ps : Command used to list the current processes. 38) kill : Command used to kill a process. 39) ssh : Command for SSH client (remote login program). 40) scp : Command for secure copy (remote file copy program). 41) fdisk : Command for partition manipulator. 42) mount : Command to mount a file system. 43) umount : Command which is used to unmount file systems. 44) du : Command to estimate file space usage. 45) df : Command to report filesystem disk space usage. 46) quota : Command to display disk usage and limits. 47) crontab -e : command to create a crontab. 48) crontab -l : command to list cronjobs. 49) ln : Command to create a symbolic link to a file. 50) locate : It's A fast database driven file locator. 51) whereis : Command to report all known instances of a command. 52) which : Command to know the path of a file/folder. 53) bg : Places the current job in the background. 54) clear : Command which clears the terminal screen. 55) dmesg : Messages resulting from the most recent system boot. 56) fg : Brings the current job to the foreground. 57) free : Displays the amount of used and free system memory. 58) ftp hostname: Opens an FTP connection to the specified host. 59) mail : Launches a simple mail client that permits sending. 60) ping host : Sends an echo request via TCP/IP to the specified host. 61) telnet host : Opens a login session on the specified host. 62) nmap Ip : To know the open ports. 63) netstat Ip : To know the open and connected port. 64) ifconfig : To know the IP details. 65) if up : Command used to up the services. 66) dig -x IP : Command used to know the hostname using IPO address. 67) dig hostname: Command used to know IP address via hostname. 68) hostname : To know Hostname ofhost -t a google.com our machine. 69) rsync : Copy specified files remotely from other machines. 70) top : Prints a display of system processes. 71) uptime : Command to prints the system uptime. 72) w : Prints the current system users. 73) wall : Prints a message to each user. 74) traceroute : Uses echo requests to print a network path to the host. 75) info : Command to view the information about any command. 76) --help : Command to view the help documents of a command. 75) dir : To view the sub directories and files under the directory. 76) su : Command used to change user. 77) ll : Command used to list the contents of directories. 78) find : To search a file in machine 79) whoami : Command shows your current logged in terminal username. 80) rpm -ivh : To install a rpm package. 81) rpm -e : To remove a rpm package. 82) rpm -qa : To list the installed rpm packages. 83) yum install : To install yum packages. 84) yum remove : To remove yum packages. 85) yum list : To list yum packages. 86) userdel : To delete a user. 87) groupadd : To add a group. 88) groupdell : To delete a group. 89) groupmod : To change the permissions of a group. 90) chage : To set the expiry of a user. 91) crontab -r : command to remove cronjobs. 92) chgrp : To change the group of a user. 93) lsattr : To view the attribute of a file/folder. 94) passwd -l : Locking a user account. 95) passswd -u : To unlocking a user account. 96) usermod : To modify the user profile. 97) nslookup : See the ipaddr or address associated with domains in DNS. 98) nano : Command to start a basic text editor. 99) finger : Get detailed information about a person who has access to the system. 100) dd : Disk duplicate. 101) tr : Command to translate the characters of a file. 102) dpkg -l : To get a list of all the installed packages. 103) cron : Daemon to execute scheduled commands. 104) fsck : Used file system checking. 105) && operator: Two or more commands can be combined with the && operator. 106) elinks URL : Surfing the net in text only mode from the terminal. 107) reboot/init 6 : Command to reboot the system. 108) poweroff/init 0 : Command to power off the system. 109) chattr -a/chattr -l: to set the attributes of a file/folder. 110) crontab -e -u : command to set cronjobs for particular users. 111) logout/Ctrl+D : To logout from a user account.