10 Interview questions for Unix/Linux System Administrators

 1. “Explain the boot process of Unix System in details”.

 Boot process (as in all Operation Systems) is crucial to know how to deal with and understand. What is BIOS and why is it there? What about MBR, LILO and GRUB? What are run-levels? How can I make the system boot with a single user mode? Perhaps the way I can boot without the graphical user interface?

Be short and simple. Give explanations and try to simulate a real life event, for instance if you need to upgrade the crucial part of the system and users should be logged off what run-level you would choose? Etc.

2. What is SWAP partition and why it is there?

 Swap is what I like to think as a “separate Ram memory”, located on disk instead. If the Ram runs out of memory, then SWAP space is used. Linux separates physical RAM into chunks called pages. It is there to support the main memory when one runs out of it.  

3. What is PID? And how do you list TOP processes and how you kill one?

PID is Process ID, and for listing CPU intensive processes you use TOP command. Kill command following the process-id will terminate the process. 

4. What is the command for showing the Operating System name or version as well as kernels version running on your system?

Command for achieving kernel version is $uname -a, and for Operating Systems version: $ lsb_release -ic

5. Permissions. How you change them? If you’ll be asked to create a file with read-only property, how can you achieve that*? 

Basic rights are: Read, Write, Execute, and their meanings are straight forward.                $chmod "permission parameters" is how you change them.                                  If you want to view permissions on specific file or folder type $ls -l "fileName"

Changing permissions in Unix/Linux environment is what administrators do every day. You should have a throughout knowledge of permissions in Linux/Unix environments.

* read only file: $chmod 440

6. LVM, VG?

Logical Volume manager is crucial aspects in Unix storage. It manages disk drives, and this allows for disks to be added or replaced without the system downtime. Volume Groups gathers LV's together.

7. Explain system backup and different backup techniques.

mksysb, tar, cpio, ufsdump to name a few.

8. Hard vs Soft (symbolic) links?

Hard links vs soft links are very simple to understand and I will write twi different scenarios for both of them:

When you create hard-links you are actually creating two separate file names pointing to the same spot on a hard drive. In contrary, when you create Symbolic (Soft) links, you are actually creating a pointer to a filename itself. This is good if you don't want to take up space, but if you need speed, then hard-link is the solution.

 9. Explain root account?

Even thou root is the administrator of the computer, you should never user root for your daily activity, user SUDO instead.

10. What is SUDO?

Sudo stands for SUPER-USER DO. It is used to run programs with security privileges of a superuser.