Linux Interview Questions with Answer

This article provides Linux interview questions with answers.

Which file have runlevel configuration?

/ect/inittab

What command would you use to shut down the system in 100 seconds?

#shutdown -h 100

What daemon controls the print spooling process?

The Line Printing Daemon (lpd) controls the print spooling process.

What configuration file defines the default runlevel for the init process?

/etc/inittab file defines the default runlevel for the init process.

Which command can you use to shut down and halt a Linux System?

The halt command will shut down a Linux system without rebooting

What init level should you set to bring the system to single-user mode?

init 1 will bring the system to single-user mode

A user wants to restart the NFS server because they want to enable changes made in the configuration file. What command accomplishes this task?

#service nfs reload

The reload command will tell the system to stop the service, reload the configuration file, and restart the service

What command can you use to reboot a Linux system?

The command to reboot a Linux system is reboot

What mode must you be in when using vi editor to input text into a file?

To insert text in the vi editor, you must be in insert mode

What runlevel does init 1 represent?

init 1 represents runlevel1.Runlevel 1 is used for single user mode.

One user from your company left the job without telling root account password of his system. To reset root password, in which mode you need to boot the system?

To reset the root password, we need to boot the system in single user mode.

What runlevel does init 2 represent?

init2 represents rulevel 2. runlevel 2 is used for multiuser without networking.

Some users are complaining that the DHCP server is not running. After examine the running processes on the system, you notice that the process is not present. What command should you use to start the DHCP service?

Because the service is currently not running, use the start command

#service dhcpd start

What runlevel does init 5 represent?

Runlevel 5 is used to boot up a full multiuser system and to automatically start X-windows.

What tar argument is used to extract files from an archive?

To extract files from an archive, use the -x argument in the tar command.

What init runlevel should be set to shut down and reboot the system?

init runlevel 6 is used to shut down and reboot the system

What command would you use to add the user name vickey?

#useradd vickey

This command will add the user viceky with default options. But this will not be able to login in system until you set a password for it. To set password use following command

#passwd vickey

Which runlevel currently not is used ?

Runlevel 4 is not used.

Your company hired a new developer for temporary periods to speed up the ongoing project. You are tasked to create a new user account which should be disabled automatically on 5 may 2014. How would you do that?

Use -e option with useradd command. -e option allows you to set the date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD. Following command will do the assigned task

#useradd -e 2014-05-05

Which command should you use to change the user information listed form finger command?

chfn command is used to change the information listed from finger command.

What runlevel does init 6 represent?

Runlevel 6 is used to reboot the system.

You are tasked to delete a user account with all his associated files including his home directory and mail folder. How will you do that ?

#userdel -r [username]

Above command will delete user account as well all his associated files including his home directory and mail folder.

A user comes to you and complain that his system was starting fine in GUI mode, but from last reboot system is starting in command line interface. What is the most likely cause of the problem?

In the /etc/inittab file, the default runlevel is probably set to 3, which tells it to start the system in command line.

What files are updated when adding a group?

/etc/group and /etc/gshadow files contains group information in Linux system. So these files would be updated every time whenever new group is added.

What command is used to delete a group?

The groupdel command will delete a group.

What runlevel does init 3 represent?

init3 represents rulevel 3. runlevel 3 is used for multiuser with networking.

What command will display the directory path that is currently in use?

pwd command will display the directory path that is currently in use.

A user type 'cd ~ ' on command prompt, what this command will do?

This command will move user to his or her home directory. ~ represents home directory in Linux.

A user comes to you and complain that his system start fine, but as soon as it is almost loaded it reboot again. What is the most likely cause of the problem?

In the /etc/inittab file, the default runlevel is probably set to 6, which tells it to reboot right after the system has started.

Which command will list all the files and sub-directories in a directory and include the access rights?

ls -l command will list all the files and sub-directories in a directory and include the access rights.

Which command will list all the files in a directory including hidden files?

ls -a command will list all the files in a directory including hidden files.

What is the correct syntax for the move command?

The correct syntax for the move command is

mv [options] [source] [destination]

Which character option with chmod command allows the execute-only permission if the file is a directory?

The x option is used to allow execute only if the file is a directory.

How will you display confirmation of the change of ownership of a file from rhuser1 to rhuser2?

Use --verbose option with chown command. For example

#chown --verbose rhuser2 /tmp/testfile

Which command is used to un-mount a DVD?

Use umount command to un-mount the DVD or CD or any other mounted media.

What runlevel does init 0 represent?

Runlevel 0 is used to halt /shutdown the system.

Which command will display the total size of all files, without listing the files, in a user's home directory?

The command du -c -s /home/user will display the total size of all files, without listing the files

Which command will display the available space of each partition in megabytes (MB)?

The command df -m will display the available space of each partition in MB.

Hard drive in your system is full and you want new hard drive. However sales department would not approve the expenditure without proof. Which tool would you use get a proof?

Use df command to justify the available free space in hard disk.

A user comes to you and complain that his system start fine, but as soon as it is almost loaded it shuts down again. What is the most likely cause of the problem?

In the /etc/inittab file, the default runlevel is probably set to 0, which tells it to shutdown right after the system has started.