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1. What is Linux?

Ans: Linux is an operating system based on UNIX and was first introduced by Linus Torvalds. It is based on the Linux Kernel and can run on different hardware platforms manufactured by Intel, MIPS, HP, etc.


2. What is the difference between Unix and Linux?

Ans: Unix originally began as a propriety operating system from Bell Laboratories, which later on spawned into different commercial versions. On the other hand, Linux is free, open source and intended as a non-propriety operating system for the masses.


3. What is LILO?

Ans: LILO is a boot loader for Linux. It is used to load Linux into the memory and start the Operating system. LILO can be configured to boot other operating systems as well. LILO is customizable, which means that if the default configuration is not correct, it can be changed. Config file for LILO is lilo.conf.


4. How to check memory stats and CPU stats as a linux admin?

Ans: Using ‘free’ & ‘vmstat’ command, we can display the physical and virtual memory statistics, respectively. With the help of ‘sar’ command, we can see the CPU utilization & other stats.


5. What is GNOME?

Ans: GNOME stands for Genious Network Object Mode Environment. It is the default environment in all the Linux distributions. It is faster than KDE but contains less applications.


6. What is KDE?

Ans: KDE stands for Kool Desktop Environment. This need to be selected at the time at login. It is slower than GNOME but contains more applications.


7. What is the combination of keys that can be used to switch the terminals/consoles?

Ans: Alt+Ctrl+{F1/F2/F3/F4/F5/F6}


8. What is the command to check the current terminal in which you are working?

Ans: #tty


9. What is Inode number?

Ans: it is also called as Index Number. It is a data structure on a traditional unix style file system such as ext3/ext4. It is an entry in inode table containing metadata information about a regular file or a directory. It contains the following attributes:
• File Types
• File Permissio
ns • UID
• GID
• File Size


10. How do you make use of alias command?

Ans: we can use alias command for making a long command shortend one.
Syntax: #alias test=”ls –l”
Here after whenever the test command is executed the linux system will take “ls –l” and displays the contents in long listing format. To remove the alias command
Syntax: #unalias test


11. What is the command to remove a directory with all its files and subdirectories?

Ans: #rm –rf


12. What are different initialization levels and what are their uses?

Ans: basically there are 7 initialization levels
• Init 0 – used for shutdown
• Init 1 – used for single user mode and also for troubleshooting mode
• Init 2 – used for multiuser performance with Command Line Interface
• Init 3 – used for multiuser performance with networking support in Command Line Interface
• Init 4 – it is unused
• Init 5 – used for multiuser performance with networking support in both Graphical User Interface and Command Line Interface
• Init 6 – used for restart
To access any of the above mentioned runlevel or initialization level just go to terminal and type

#init <0,1,2,3,4,5,6>


13. What is GRUB or GNU GRUB in Linux?

Ans: GNU GRUB or just GRUB is a boot loader package that supports multiple operating systems on a computer. During boot-up, the user can select the operating system to run. GNU GRUB is based on an earlier multiboot package, GRUB (GRand Unified Boot loader). GRUB is most often used on Unix-like systems, including GNU, Linux and Solaris.


14. What is the command used for file permissions and advanced file permissions?

Ans: for basic file permissions: #chmod
For advanced file permissions: #setfacl –m


15. What is the home directory of a root user?

s: An/root


16. What is the home directory of users other than root user (ex: sam)?

Ans: /home/
For user by name Sam the home directory will be : /home/sam


17. What is RAID and what are the types of RAID available in Linux?

Ans: RAID stands for Redundant Array Inexpensive Disks. There are 4 types of RAID
• RAID 0 - Stripping without Parity
• RAID 1 – Disk Mirroring
• RAID 4 - Parity
• RAID 5 – Stripping with Parity


18. What is the command used to check the free disk space in linux?

Ans: #df –hT


19. What is tar?

Ans: TAR stands for Tapes ARchiver. Itis used to archive a directory and save it in some other location. Even if the original data is lost we can backup using the tar archived file


20. What is CPIO?

Ans: CPIO starts for CoPy Input Output. It is used to take the backup of the selected files in some other specified location. Steps involved in backing up of data using cpio command:
#ls | cpio –ov >
• To restore the files from the .cpio file
#cpio –iv < <.cpio file path>
• To view the contents in the .cpio file
#cpio –tf < <.cpio file path>