Linux System Admin Interview Questions and Answers

   Q-1: - How are devices represented in UNIX?

   Ans: - All devices are represented by files called special files that are located in /dev directory.

   Q-2: - What is inode?

   Ans: - All UNIX files have its description stored in a structure called 'inode'. The inode contains          info about the file-size, its location, time of last access, time of last modification, permission and so    on. 

Q-3: - What are the process states in Unix?

Ans: - As a process executes it changes state according to its circumstances. Unix processes have the following states:

Running : The process is either running or it is ready to run .Waiting : The process is waiting for an event or for a resource.Stopped : The process has been stopped, usually by receiving a signal. Zombie : The process is dead but have not been removed from the process table.

Q-4: - What command should you use to check the number of files and disk space used and each user's defined quotas?
Ans: - repquota 

Q-5: - What command is used to remove the password assigned to a group?
Ans: - gpasswd -r

Q-6: - What can you type at a command line to determine which shell you are using?
Ans: - echo $SHELL

Q-7: -  Write a command to find all of the files which have been accessed within the last 30 days.Ans: - find / -type f -atime -30 > filename.txt

Q-8: - What is a zombie?
Ans: - Zombie is a process state when the child dies before the parent process. In this case the structural information of the process is still in the process table.

Q-9: - What daemon is responsible for tracking events on your system?
Ans: - syslogd 

Q-10: -  What do you mean a File System?
Ans: - File System is a method to store and organize files and directories on disk. A file system can have different formats called file system types. These formats determine how the information is stored as files and directories.

Q-11: -  Tell me the name of directory structure hierarchy for Linux
Ans: -
/root
/boot
/bin
/sbin
/proc
/mnt
/usr
/var
/lib
/etc
/dev
/opt
/srv
/tmp
/media  

Q-12: - What does /boot directory contains?
Ans: - The /boot/ directory contains static files required to boot the system, such as the Linux kernel, boot loader configuration files. These files are essential for the system to boot properly. 

Q-13: - If some one deletes /boot directory from your server, than what will happen?
Ans: - In that case your server will be in unbootable state. Your Server can’t boot without /boot directory because this directory contains all bootable files 

Q-14: - What does /dev directory contain?
Ans: - The /dev directory contains all device files that are attached to system or virtual device files that are provided by the kernel.

Q-15: -  What is the role of udev daemon?Ans: - The udev demon used to create and remove all these device nodes or files in /dev/ directory. 

Q-16: - Tell me the name of device file for PS/2 mouse connection.

Ans: - /dev/psaux

Q-17: - Tell me the name of device file for parallel port (Printers).

Ans: - /dev/lp0 

Q-18: - What does /etc/X11/ directory contains?

Ans: - The /etc/X11/ directory is for X Window System configuration files, such as xorg.conf.

Q-19: - What does /etc/skell directory contains?

Ans: - The /etc/skel directory contains files and directories that are automatically copied over to a new user's home directory when such user is created by the useradd or adduser command.

Q-20: - Tell me name of Linux File systems?

Ans: - Ext2, Ext3, Ext4.

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