100 Linux Interview Questions

100 Linux Interview Questions for Beginners in 2019

Linux Interview Questions and Answers

Are you looking for Linux interview questions? Hope you are in the right place to get most of the entry-level interview questions. The below questions are framed for those who are certified or not certified with minimum knowledge in Linux. The explanation for each question will be updated in the future with links referring to each answer.

Go through all the Linux Interview questions to make sure yourself prepared.

100 Linux Interview Questions
100 Linux Interview Questions

The commands that start with the “#” symbol need to be run from a privileged superuser (admin) account. Starting with “$” commands can be run from any unprivileged accounts (Normal users).

Date/Time/Timezone/NTP Management

How will you print the Date & time in Linux?

$ date

2. Which daemon will handle time synchronization in Red Hat Linux 7, Centos 7, Oracle Linux 7?


3. How will you set the Date/time on a Red Hat 7/8, CentOS 7, Oracle Linux 7/8?

# timedatectl

4. Protocol / Port number used by NTP?

UDP / 123

5. What command is used to list only the directories?

$ ls -d

6. How to find how long a server running?

$ uptime

Linux Permissions

7. How to change files mode permission in Linux?

# chmod

8. How to change ownership of a file in Linux?

# chown

9. What is SetUID, SetGID?

The setuid is a permission that allows the users to execute a program with the permissions of its owner. The setgid is a permission that allows the user to exec a program with the permissions of the group owner.

10. How to list and change the access control list of a file.

# getfacl file_name
# setfacl file_name

11. Explain what will chmod 640 file_name do?

Provide Read, Write access for the user, Read access for the group, no permission for others.

12. Set GID with any permission for /home/sysadmin/test.txt

# chmod 2774 /home/sysadmin/test.txt

13. What is the default permission for a file when created in Linux.


Note: This depends on umask.

Linux File Systems & Partitioning

14. How to create an ext4 filesystem

# mkfs.ext4 /dev/device_name
# mkfs -t ext4 /dev/device_name

15. What is the default file system of RHEL 7, Centos 7, Oracle Linux 7?

# xfs

16. Default home directory of root user will be under which location?


17. How will you partition a disk in Linux?

# fdisk /dev/disk_name

Read more about how to partition using fdisk by clicking on FDISK to partition the disks in Linux

18. How to create a Logical Volume using Physical extends?

# lvcreate -l 43232 -n some_name vg_name

-l will be used to create using extends

For a deep understanding of how Logical volume management works refer to Create Logical volume management LVM file-system in Linux

19. How to remove volume groups from a Linux server?

# vgremove vg_remove

20. What are the steps need to be followed to create a logical volume in Linux?

# fdisk /dev/disk_name
# pvcreate /dev/disk_name
# vgcreate name /dev/disk_name
# lvcreate -n lv_name vg_name

21. Which command is used for creating a swap?

# mkswap /dev/dev_name

22. How will you mount a file system?

# mount /dev/dev_name /mount_point

Read more about Creating and mounting filesystems in Linux

23. Which command will list the UUID of all block devices?

# blkid

24. How to activate and deactivate a swap?

# swapon /dev/device_name
# swapoff /dev/device_name

25. How to display total disk usage of the current directory?

$ du -sh

26. How to make a file system persistent during reboot?

Adding entry in FSTAB

27. The maximum number of  Primary Partitions can exist on one drive?


28. How to list the available mount points in Linux in human-readable format?

# df -hP

29. Which command is used to list the available NFS exports from client machines.

# showmount -e server_IP

User Management

30. How to change the shell of a user?

# chsh -s /bin/bash user_name 

31. How to check the aging of a User in Linux

# chage -l user_name

32. How to create a user with UID 5000

# useradd -u 5000 user_name

33. Which command can be used to modify user information?

# usermod

34. How to remove a user from a Linux server?

# userdel user_name

35. Default UID of root user?


36. How to print user information’s UID, GID, and Groups?

$ id user_name

37. How to remove a group from Linux servers.

# groupdel group_name

38. How to lock a user password

# passwd -l username

39. In which file, all recently entered commands will be stored?


Linux Networking

40. How to configure IP using TUI/CLI?

# nmtui
# nmcli

41. How to bring an interface up or down without restarting or affecting other interfaces?

# ifup ens33
# ifdown ens33

42. How to print the host-name in Linux with short and FQDN format?

# hostname -s
# hostname -f

43. How to set the hostname in RHEL 7 Linux?

# hostnamectl set-hostname some_name_here

44. Which command will print the gateway information in Linux?

# route -n
# netstat -nr
# ip route

45. The default location of the interface files will be under.


46. Which file will show all Services, protocol, and Port numbers in Linux?

$ cat /etc/services

Package & Repository Management

47. What is YUM? Abbreviation of “YUM”?

Yellowdog Update Manager or Modifier

Learn how to use the YUM command for package management by referring to the 31 Yum command for Package Management in Linux

48. How to list all installed packages using the rpm command.

# rpm -qa

49. Which package was used for setting up an Apache webserver


Service Management

50. How to restart a service in RHEL 7, Oracle Linux 7, Centos 7

# systemctl restart service_name

51. How to completely disable a service from manually starting and at boot time.

# systemctl mask service_name

52. How to get and change the run level in RHEL 7

# systemctl get-default
# systemctl set-default run_level

53. Which command was used to change the priority of a process

# renice

Managing Jobs

54. How to run a Job in the background?

some_job &

55. How to bring the background Job to the foreground?

# jobs

Run the command jobs then

# fg job_ID

Linux Signals

56. What will CTRL+C and CTRL+Z do?

CTRL+C Sends a signal to interrupt (SIGINT) the foreground process; CTRL+Z will send a Suspend (SIGTSTP) the foreground process to background.

57. What is the signal number for CTRL+C


58. What is the signal number of CTRL+Z


Linux Security

59. Which command is used to create an ssh Key?

$ ssh-keygen

60. Full form for TLS?

Transport Layer Security (TLS)

61. How will you check the status of SELinux?

# sestatus

62. How to list the SELinux context of /var/www/html directory.

$ ls -lZ /var/www/html

If you are not good with SELinux it’s time to start right now by visiting How to start using SELinux or Security-Enhanced Linux

63. Command used to secure copy a file over the network.

$ scp

64. How to synchronize two directories securely in Linux?

$ rsync

Listing files | Locating files| Config files

65. How to list all hidden files in a directory?

$ ls -la

66. Which command will print the present working directory?

$ pwd

67. How to complete the command in the terminal by auto-completion?


68. The default location of the Apache configuration file.

$ ls -lthr /etc/httpd/conf/httpd.conf

Read How to install Apache Web Server on Red Hat Enterprise Linux 7 and Variants for knowing more about Apache.

69. Default document root location of Apache Web server?


70. How to list the first 25 lines of a file.

$ head -25 filename

71. How to list the last 50 lines of a file.

# tail -50 /var/log/messages
# tail -n 50 /var/log/messages

72. How to create a soft link for file /home/linuxsysadmins/linux.txt under /var/www/html/

$ ln -s /home/linuxsysadmins/linux.txt /var/www/html/linux.txt

73. The default location of repository file in RHEL, Centos, Oracle Linux 7?

$ ls -ld /etc/yum.repos.d/

74. Which command is used to determine the path of an executable file?

$ which service_name

75. How to find and list all files owned by user “sysadmin” in his home directory.

# find /home/sysadmin/ -user sysadmin -f type -exec ls -lthr {} \;

76. Under which location wiki pages will be stored?


77. What will echo “some text” do?

Prints "some text" in screen.

78. How to search for a string starting with sysadmin in the file /etc/passwd?

$ grep "^sysadmin" /etc/passwd

Linux Schedulers

79. How to Schedule and list some tasks for user sysadmin in Linux?

# crontab -u sysadmin
# crontab -l -u sysadmin

80. How will you schedule a one-time task in Linux

# at

Linux Archive & Compress

81. Which command is used to archive a file in Linux.


82. The single command used to archive and compress files or directories in Linux?

$ tar zcvf

Linux Boot | Kernel | System Information

83. How to know the kernel version of Linux?

# uname -r

84. What will happen after bootstrapping?

Starting with Init.    (0)         # RHEL 6.x
Starting with Systemd. (1)         # RHEL 7.x / 8.x

85. How to print full memory information?

$ cat /proc/meminfo

86. How to print full CPU information?

$ cat /proc/cpuinfo

87. How many run levels are in Linux?

Total 7 run levels, 0-6

88. What is the load average? and explain each section.

5, 10, 15 minutes CPU's are busy.

Linux Editors

89. In vi editor which command sets the number for all lines?

:set nu
:set number

90. How to exit vi editors in Linux?


91. Which command will be used to count the total number of lines, words, and characters in a file?

$ wc

SSH Configuration

92. Default port number of SSH?


93. How to ssh into a server with IP address using user sysadmin

$ ssh sysadmin@

Linux Interview Questions on Miscellaneous

94. The maximum allowed characters in a filename in Linux?


95. How “anaconda-ks.cfg” will be created under /root ?

Anaconda installer will create “anaconda-ks.cfg” after completing with post installations.

96. The command/package used to create an iSCSI server.

# targetcli

97. What is Samba and why is it used?

Samba used to connect with Windows machines and used as a file-sharing protocol and print service.

98. How to set a variable in shell scripting?

var=uname -a

99. How frequent /tmp gets cleared automatically?

10 days old

100. How to display all currently running processes on any Linux system.

$ ps -ef

Hope this post helps you for preparing your admired Linux admin role. Read all entry-level Linux Interview questions to prepare yourself before appearing in any interview.