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.

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