1. How To Check The Uptime Of A Linux Server?
Using uptime command we can determine how long a linux box has been running , also uptime can be viewed by the top & w command.

2. How To Check The Ip Address Of Lan Card?
Using ‘ifconfig’ & ‘ip address’ command we can determine the ip address of LAN Card.

3. How To Check The Default Gatway?
Using ‘route -n’ command we can determine the default gateway in linux.

4. What Is Initrd ?
Initrd stands for initial ram disk , which contains the temporary root filesystem and neccessary modules which helps in mounting the real root filesystem in read mode only.

5. How To Check Which Redhat Version Is Installed On Server?
Use the command cat /etc/redhat-release , output of this command will tell you the redhat version.

6. Why Linux Is Called Opensource?
Because One can customize the existing code and can redistribute it.

7. What Is The Default Uid & Gid Of Root User?
Default uid & gid of root user is 0.

8. How To Check The Current Runlevel Of A Linux Box?
‘who -r’ and ‘runlevel’ , both of these command are used to find current run level.

9. How To Install Rpm Packages In Redhat & Centos Linux ?
rpm and yum command are used to install packages in redhat linux and CentOS.

10. What Is Bootloader?
Bootloader is a program that boots the operating system and decides from which kernel OS will boot.

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11. What Is Name Of First Process In Linux?
‘init’ is the first process in linux which is started by kernel and whose pid is 1.

12. How To Change The Password Of User From The Command Line?
‘passwd <User-Name>’

13. How To Determine The Hostname Of A Linux Box?
On typing the hostname command on terminal we can determine the hostname of a linux server.

14. How To List Hidden Files From The Command Line?
‘ls -a’ <Folder_Name>

15. What Is Run Level 2?
Run level 2 is the multi-user mode without networking.

16. Which Command Is Used To Check The Kernel Version ?
‘uname -r’

17. What Is A Process?
Any program in execution is called a process.

18. What Are The Run Levels In Linux And How To Change Them?
A run level is a state of init and the whole system that defines what system services are operating and they are identified by numbers.There are 7 different run levels present (run level 0-6) in Linux system for different purpose. The descriptions are given below.
0: Halt System (To shutdown the system)
1: Single user mode
2: Basic multi user mode without NFS
3: Full multi user mode (text based)
4: unused
5: Multi user mode with Graphical User Interface
6: Reboot System
To change the run level, edit the file “/etc/inittab” and change initdefault entry ( id:5:initdefault:). If we want to change the run level on the fly, it can be done using ‘init’ command.

19. What Is Soft Link?
Soft link is a method to create short cuts in linux. It is similar to windows short cut feature.

20. What Is Selinux?
SELinux is an acronym for Security-enhanced Linux. It is an access control implementation and security feature for the Linux kernel. It is designed to protect the server against misconfigurations and/or compromised daemons. It put limits and instructs server daemons or programs what files they can access and what actions they can take by defining a security policy.

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