Phenquestions
1. Cat (Concatenate)
This command can be used to get the contents of the file as an output in the Terminal window. You just need to write the cat command as shown sample screenshot and execute it.
As the name suggests this command can be used to create, view and concatenate files.
If the file is longer than the size of Terminal window then it will be not easy to read or view all the content of the file easily. But there is a tweak, you can use less with cat command. It will give user an ability to scroll forward and backward through the content of the files using PgUp and PgDn keys or Up and Down Arrow keys on the keyboard.
Finally to quit from the less you can just type in q.
2. aptitude
aptitude is highly powerful interface for Linux package management system.
First of all you need to install or update aptitude package in your system using following command.
Once the installation is complete you can type aptitude in Terminal and execute it, this will open up aptitude interface as you can see in screenshot below.
You can use this aptitude built-in interface to update, install or remove any application package on Linux or its other distributions.
3. cal
You can use cal command in Terminal window to see the calendar, as you can see in the following screenshot I have executed command to view the calendar of the current month and you can notice it highlighted the date as well.
You can also view the calendar of an entire year by executing command shown in following screen shot.
4. bc
bc is another cool and useful command for Linux users as it allows you to enable command line calculator in Linux Terminal when you execude following command.
You can make any calculation in Terminal window itself, isn't that cool command to have at your service?
5. chage
The Linux command chage is an acronym for change age and it can be used to change the expiry information of the user's password.
As you can see in the above screenshot you can also force the user to change the password after certain period of time i.e. periodically. This is an excellent command for system administrators.
6. df
You can get all the information of your file system just by executing df command in the Terminal window.
If you use df -h it will display file system information in human readable format as you can notice in following screenshot.
7. help
When you execute this help command in Terminal window, it will list all built-in commands you can use in shell.
8. pwd (Print Work Directory)
As the name Print Work Directory suggests, this command the path of the directory currently you're working in. This command is very useful for all the Linux noobs and those who are new to Linux Terminal.
9. ls
I think I don't need to introduce to this command as this is one of the commonly used commands in Terminal by Linux users.
When you type and execute ls command in Terminal, it will show you all the contents of the particular directory i.e. both files as well as directories as you can see in above screenshot.
10. factor
factor is a mathematical command for Linux terminal which will give you all the possible factors of the decimal number you enter in the shell.
11. uname
uname is another useful Linux command to have as it displays Linux system information when executed in Terminal shell.
To view all system information type uname -a in Terminal.
For information related to kernel release only just type in uname -r.
And for operating system information type uname -o in Terminal shell.
12. ping
If you want to check if your system is connected to router or internet then PING (Packet INternet Groper) is the command for you. It uses ICMP protocol to connect to other devices.
There are several options to use with ping command, ping displays addresses as host name so if you want to view them in numbers then use ping -n command. Ping -I to specify the interval between transmissions as it is 1 second by default.
13. mkdir
mkdir
You can also use rmdir
14. gzip
You can compress any file from Terminal window using gzip
15. whatis
If you wish to know for what the particular Linux command can be used for then just execute the command whatis
16. who
This one is for system administrators who handle and manage various users on Linux system. who command when executed in Terminal show the complete list of those users who are currently logged into Linux system.
17. free
free command can be used to check exactly what amount of storage is free and used in physical as well as swap memory in the system.
There are also some options to use with free command such as you can use free -b to view the results in bytes, free -k to display the available and used in memory in kilobytes, free -m to to view in megabytes, free -g to view results in gigabytes and free -tera to view the results in terabytes.
18. top
top is simple but useful command to monitor all the ongoing processes on the Linux system with the user name, priority level, unique process id and shared memory by each task.
19. sl
This one is just for bit fun during the work and not a useful command. When executed a steam engine passes through Terminal window. You can try it for fun!
If you are unable to see it then use the following command to install it.
$ sudo apt install sl
20. banner
banner is another fun command for Linux Terminal when executed with banner
21. aafire
How about putting the Terminal window on fire? Just fire the command aafire in the Terminal window and see the magic.
$ sudo apt-get install libaa-bin
22. echo
echo command can be used to print any text you through with the command as you can see in the below screenshot.
23. finger
finger
24. groups
If you want to know which groups the particular user is member of then execute groups
25. head
This command will list the first 10 lines of the file you through with head command in the Terminal window. If you want to see particular number of lines then use -n (number) option like head -n (any number)
26. man
Here man stands for user manual and as the name suggests man
27. passwd
You can use passwd command to change the password for self or any user, just through the command passwd if you want to change password for youself and passwd
28. w
w is the short and simple command which will help you view the list of currently logged in users.
29. whoami
This command will help you to find out which user is logged into system or who you are logged in as.
30. history
When fired into Terminal shell, history command will list all the commands used by you in serial numbered form. Using exclamation mark ! and serial number of the command will help you execute that particular command without need to writing whole command in the terminal.
31. login
If you want to switch user or want to create new session then fire this command in Terminal window and provide the details like login id and password as shown in screenshot below.
32. lscpu
This command will display all the CPU architecture information such as threads, sockets, cores and CPU count.
33. mv
mv (move) command can be used to move one file or directory to another file or directory. It is very useful command especially when you're working on system administration.
34.ps
If you want to see the list of processes that are currently running for your session or for other users on the system then ps command is for you as it shows processes with their process identification numbers and in detail as well when you use ps -u command.
35. kill
You can use this command to kill the currently ongoing processes manually form the Terminal shell itself. You need unique PID i.e. process identification number to kill the process.
36. tail
tail
37. cksum
cksum is a command to generate the checksum value for the file or stream of data thrown with command in Linux Terminal. You can also whether the download is corrupted or not if you are facing problem in running it.
38. cmp
If you ever need to do byte-by-byte comparison of the two files then cmp
39. env
env is a very useful shell command which can be used to display all the environment variable in the Linux Terminal window or running another task or program in custom environment without need to make any modifications in current session.
40. hostname
hostname command can be used to view the current host name and hostname
41. hwclock
You can use hwclock or hwclock -set -date
42. lshw
sudo lshw command can be used to invoke detailed hardware information of the system on which Linux is running. It gives you every small detail about hardware, just try it.
43. nano
nano is Linux command-line text editor just similar to Pico editor which many of you might have used for programming and other purposes. It is quite useful text editor with lots of features.
44. rm
rm
45. ifconfig
ifconfig is another useful Linux command which can be used to configure network interface on the system.
46. clear
clear is simple command for Linux Terminal shell, when executed it will clear the Terminal window for fresh start.
47. su
su
48. wget
wget
49. yes
yes “your text” command is used to display a text message entered with yes command repeatedly on Terminal window until you stop it using CTRL + c keyboard shortcut.
50. last
When executed last command will display the list of last logged in users into the system as an output in Linux Terminal.
51. locate
locate command is an reliable and arguably better alternative to find command to locate any file on the system.
52.iostat
If you ever need to monitor system input/output devices then iostat command can be very useful for you as it displays all the stats of the CPU as well as I/O devices in Terminal window itself.
53. kmod
You can use kmod list command to manage all the Linux Kernel modules as this command will display all the currently loaded modules on the system.
54. lsusb
lsusb command will show information about all the USB buses connected to the hardware and external USB devices connected to them as you can see in screenshot below.
55. pstree
pstree command displays all the currently running processes in the tree format on Linux Terminal window.
56. sudo
If you need to run any command as a root user or root permissions then just add sudo at the start of any command.
57. apt
apt (Advanced Package Tool) is Linux command which helps user to interact with the packaging system as you can see in following screenshot.
58. zip
You can use zip command to compress one or more files as you can see in the screenshot below. It is simple but useful command to compress any number of files in a go.
59. unzip
To extract files from compressed zip file use unzip
60. shutdown
You can use shutdown command to turn of the system directly from Terminal shell. This command will shutdown the system exactly one minute after being executed. You can use shutdown -c command to cancel shutdown.
61. dir
dir (directory) command can be used to view the list of all directories and folders present in current working directory.
62. cd
cd command helps you to access particular directory or folder from the file system. You can also use cd… command to go back to root.
63. reboot
As the name suggests you can use reboot command to restart or shutdown the system from the Terminal window. There are several options available with this command as you can see in following screenshot.
64. sort
sort
65. tac
tac
66. exit
exit command can be used to close the Terminal shell window directly from the command-line.
67. ionice
ionice command will help you get or set I/O scheduling class and priority for the particular process.
68. diff
diff
69. dmidecode
There are many commands available for Linux to retrieve hardware information but if you want information of a particular hardware component then dmidecode is the command for you. It offers various options and you can view them using dmidecode -help.
70. expr
If you want to perform quick calculations during your work then expr is really useful command for you. You can do calculations as shown in below screenshots with more options.
71. gunzip
gunzip
72. hostnamectl
hostnamectl command can be used to access system information, change the system hostname and other related settings.
73. iptable
iptables is a simple Linux Terminal based firewall tool which helps manage both incoming and outgoing traffic using tables.
74. killall
killall
75. netstat
This command is for those who need to monitor incoming and outgoing network connections continuously. netstat command displays the network status, routing tables and interface statistics.
76. lsof
lsof command will help you view all the open file related to your application in the Linux Terminal window itself. There are several options to customize the output and you can see the whole list in the below screenshot.
77. bzip2
You can use bzip2
78. service
service command will display results of System V init scripts in the Terminal window. You can view the status of particular service or all the services as shown in below screenshot.
79. vmstat
vmstat command will display systems virtual memory usage on Terminal window.
80. mpstat
When executed mpstat command will display all the information about CPU utilization and performance stats on Linux Terminal window.
81. usermod
If you want edit or modify attributes of already created user account then usermod
82. touch
Using touch command in Terminal window you can create empty files in file system and you can also change time and date i.e. is timestamp of recently accessed files as well as directories.
83. uniq
uniq is a standard Linux Terminal command when thrown with file, filters the repeated lines in the file.
84. wc
wc command reads the file thrown with the command and displays word and line count of the file.
85.pmap
pmap
86. rpm
rpm -i
87. ssh
ssh acronym for Secure Shell is protocol which is used to securely connect to host system. ssh [email protected]
88. telnet
telnet command uses telnet protocol to connect to another system as a user.
89. nice
If you need to change the priority of the running processes then run nice [OPTION] [COMMAND [ARG]… ] in the Linux Terminal.
90. nproc
nproc [option] command will display the number of processing units allotted to the currently running process.
91. scp
scp acronym for Secure Copy is the Linux command which can be used to copy files and directories between hosts on the network.
92. sleep
sleep
93. split
If you need to breakdown large file into small file then use split [option]… [file [prefix]] command in the Linux Terminal.
94. stat
You can view the status of a file or an entire file system using stat
95. lsblk
lsblk command reads the sysfs filesystem and displays the block device information on the Terminal window.
96.hdparm
Using hdparm command you can handle hard disk and other disk devices in the Linux using Terminal shell.
97. chrt
chrt [option] priority [argument… ] command is used for manipulating the real-time attributes of the process.
98. useradd
useradd [optaons] login command will help you add user account into your system
99. userdel
userdel [option] login command will let you delete any user account from the system.
100. usermod
Using usermod [options] login command you can modify any user account present on the system.
So these are the 100 essential Linux commands which can be useful for any regular as well as pro Linux user. Feel free to share your views and suggestions at @LinuxHint and @SwapTirthakar.
