Linux Interview Questions with Answers
Certiology’s Free Linux interview questions with answers are exactly what you need to prepare for linux administrator interview.
1. What is the full form of GNU?
Ans: GNU is NOT UNIX (It’s also known as a recursive acronym)
2. In Linux what is the usual size we use for swap partition?
Ans: Recommended size is twice the amount of physical memory but if shortage of memory, then at least the same size of memory.
3. Which command is used to change permissions on Linux?
4. The system configuration in Linux is stored under which path?
5. The command used to change password is _________________
6. Which Linux Service or server configuration is used for Linux and Windows to communicate or share files?
Ans : Samba is used for SMB and CIFS systems.
7. Which command is used to customize a command? Eg. To use ‘cls’ instead of ‘clear’
Ans: You need to make the modification in /etc/bashrc and use the alias command.
8. Why you should prefer using ssh over Telnet to connect to a Linux system remotely?
Ans: In Telnet data is sent as plain text thus the password can be easily snipped over the network so its recommended to use ssh.
9. _______________ Utility is used for repairing a corrupted file system.
10. During the Linux boot up, some messages are seen which show the services started as OK or FAILED. How can you see the messages that were already scrolled up.
Ans: These messages are known as kernel boot messages and stored in /var/log/dmesg
11. General system log messages are stored in which path?
12. What is full form of SMTP and why is it used ?
Ans: SMTP stands for Simple Mail Transfer Protocol and is used for sending emails.
13. _____________ is a service of Sendmail used for transferring mail from one network to other or one host to other.
Ans: MTA (Mail Transfer Agent)
14. Which is the command used to monitor system activities?
15. ____________ Command is used to change permissions of folders and files.
16. Which ports should be open on a firewall for an email server?
Ans: Port 110, 143 and 25
17. Which ports should be open on a firewall for an Web server?
Ans: Port 80 and 443
18. TFTP uses which port number ________
19. _________ And __________ are used in Linux as scheduler ( talk or job scheduler).
Ans: at and cron
20. To find users show have logged into a Linux system and their login attempts _________ or ________ command is used.
Ans: ‘w’ or ‘who’
21. ____ command is used to rename files in Linux
22. Protocol number for TCP is ______ and for UDP is __________
Ans: TCP: 6 and UDP 17
23. SNMP works on which port number?
Ans: 161 and SNMP traps 162
24. _________ Command in Linux is used to check the configured IP address and other IP information like gateway, subnet mask etc.
25. A harddisk speed is measured in RPM, what does it stand for ______________
Ans: Revolutions per minutes
26. To configure your linux machine as a router what command can be used?
Ans: we can use the ip_forward option with setting it to 1. (Echo 1 > /proc/sys/net/ipv4/ip_forward)
27. What is the UID and GID of a root user?
Ans Zero (0), bith UID and GUID are zero.
28. You use the mount command to mount a drive / path, how to you make it persistent to reboots.
Ans: by making an entry for the path in the /etc/fstab path.
29. ________ command is used to make partitions
30. _________ command updates the partition table
Ans: part probe
31. Can data be written to a disk after partitioning and not formatting it?
Ans: No data cannot be written until it is formatted with a file system
32. _______ Command is used to check size or free space or consumed space on the Linux box.
Ans : df –h
33. RPM in Linux packages stands for ____________________
Ans: Redhat pluggable modules
34. ______ cpmmand is used to check if a package is installed on the Linux box
Ans : rpm –qa ( query all)
For selective: rpm –qa | grep samba -> return only samba related output
35. Which command helps see RAM details?
36. Which command is used to remove swap?
37. MBR stands for _____________
Ans: Master Boot Record
38. What is the MBR size : ___________
Ans: 152 bytes
39. What is full form of LILO :___________
Ans: Linux Loader
40. _______________ is a chain of processes where output of one process is used as input for other
41. _____ command is used to find DNS related info in Linux.
Ans: dig and nslookup
42. To check the connectivity of two devices ro the network, ________ command is used.
43. The username and password is stored in which file _____________
44. _________ command is used to change priority of jobs.
Ans: nice command
45. To add a new user name harry what is the command used?
Ans: useradd harry
46. MySql database dump is taken using ______ command
Ans: Mysqldump databasename > dumpname
47. What is the full form of AIX in terms of IBM AIX servers?
Ans: Advance Inetractive Executive
48. Unix was invented by ______________ and __________________
Ans: Denis Ritche and Ken Thompson
49. ________________ command is used to add groups
50. _______ Folder contain base executables that are necessary for minimal function of the system.
51. __________ Command is used to delete files.
52. _________ command is used to remove a directory
53. To make logs gets rotated automatically which command is used ____________
54. _________ command is used to make a file system in Linux
Ans: mkfs (Make File System)
55. Full form of BASH is _________
Ans: Boyrne Again Shell
56. A file transfer protocol that is connectionless protocol is ______________
57. What is LVM and why is it required?
Ans: It means Logical Volume Manager and is used for resizing of file systems.
58. Port number for Squid Proxy is ___________
59. ________ command is used to check the default route
Ans: netstat –rn
60. __________ can be used only for files and not for directories
Ans: hard link
61. How may run levels are available in Linux?
62. What is run level 5?
Ans: Multi user mode with GUI
63. SeLinux means?
Ans: Security Enhanced Linux
64. GRUB stands for _______________
Ans: GRand Unified Boot Loader
65. The man command is used to see __________
Ans: the manual pages
66. RAID stands for _____________
Ans: Redudant Array of Inexpensive Disks
67. While using gdb for debugging a command BT is used, what does this mean?
68. To make a service start on startup what command is used?
69. In Linux you can create many partitions, what is the minimum number of partitions required and which are those ?
Ans: minimum 2 partitions namely, root (/) and swap.
70. UIDs from which number can be used for normal users and accounts.
Ans: From 100-999
71. To know the current dat what is the command used?
72. What is the main difference between TCP and UDP protocol?
Ans: TCP is connection oriented and UDP is connection less.
73. To run a job in background what operator is used?
Ans: Ampersand ( &) . eg. Cp source destination & (the copy will run in background)
74. _____ command is used to list files and directories.
Ans: ls –l
75. To create a 0kb file what command is used?
76. What does r, w, and x means in reference to file names?
Ans: r : Read, w : write, x : execute
77. What is the value associate with rwx?
78. Full form of FIFO is _______________
Ans: First In First Out
79. ___________ system call creates a new process
Ans: fork ()
80. ________ system call gets the parent process identifier
81. To see last 10 line of a file what command is used?
Ans: tail -10 ( eg. Tail -10 /var/log/svlog shows last 10 lines of this file)
82. The ___________ is used to dynamically assign IP address to a client
Ans: DHCP Server
83. What are the process states in Linux?
Ans: Running, Interruptible, uninterruptable, stopped and Zombie.
84. What is a Zombie process?
Ans: It is a process which is terminated but the table still has the process information
85. What is full form of YUM and why is it used?
Ans: YUM: Yellow dog Updater; it is used for installation of packages.
86. The _____________command is used to install packages using yum
Ans: yum install < package name>
87. To install a package using rpm what is the command used? Example install ftp
Ans: rpm –ivh < package name>
88. The ________________command is used to list ACLs for a file..
Ans: getfacl < filename>
89. Ext 3 is better than ext 2 because it supports a main point called_____________
90. Can we convert ext2 to ext3? If so by which command?
Ans: yes we can use the command tune2fs
91. What does CUPS stand for in Linux / UNIX?
Ans: Common Unix Prining system
92. Which RAID is considered as Mirroring?
Ans: RAID 1
93. _____________server is used with BIND package
94. __________command is used to create an archive of files and folders?
Ans: tar –cvfz
95. The TCP 3 way handshake consists of which steps:
Ans: SYN, SYN + ACK and ACK
96. _________________ is a very popular version control system
97. How do you bring down eth0
Ans: ifcfg ethdown
98. Full form of Ping is _______________________
Packet Internet Groper
99. ______________________ Command help troubleshoot by showing how many hops it took to reach a destination.
Ans :-> traceroute < destination>
100. DIG command is used to query DNS related information. DIG stands for :
Ans: Domain Internet Groper
101. As per the company policy you want the user ‘munjal’ to change the password at next logon, how do you force him to do that.
Ans: chage –d 0 “munjal”