Linux Interview Questions:

Linux interview questions in linux operating system?

1). 

How to troubleshoot the linux kernel panic issue ?

. Boot into the os for rescue mode

. log into the root user

. navigate  to the /boot

. here , initrdfs filesystem are available or not ( if this fs are available , the system is corrupted)

. we can execute the command like as the ,

initrd_initramfs_kernel_version

then reboot the operating systems ..

2). While booting your linux os , Its shows intramfs  is not working in linux os  .what you  will do in that

scenario? How do troubleshooting this issue ?

1).. We need to repair the filesystem in the corruputed partions.

using fsck command in linux os:

The steps are below ...

blkid command = It will give for all the partition types..

/dev/sda

/dev/sdb

/dev/sdc

we don't know which partition is not working properly

so that's why we need to check this partions one by one 

using fsck command ..

In this way we can figure it out which is not working 

fsck -y /dev/sda

once filesystem checking is finished , then we can reboot your os ..

Iam executing the command like ,

blkid command 

fsck -y -a /dev/sda 

then reboot the os 

3). How t extend the filesystem in linux ?

resize2fs /dev/sda

:using this command we can extend the fs:

ext , ext2 ,ext3 ,ext4

fxs_growfs command 

so we can extend the xfs filesystem using this command

4).

How to check open ports in linux os ?

we can execute the command like as a ,

netstat -tunlp command 

tunlp - t = tcp ports

u= udp ports

n=numerical address

l=listening ports

5). what is the umask ?default value of umask? where is the

location of umask ?

umask : file special permission 

whenever we will crated the file or directory

automatically umask value is assigned

default umask is 022 0022,077

location of umask :  vi /etc/login.defs file

here only we can see the umask value :

maybe if youw want we can change it 

6).How to configure the nfs server?

7).what is the samba server?

8). If we are the using ping address we can ping 

like ping www.google.com

which protocol  are using behind this ?

its a icmp protocol(Interent management control protocol)

port number:25

use of icmp :

9). I am unable to login the root user in linux os ? so how to troubleshoot it?

10).How to cretae password less authendication in ssh in linux os?

we have to genrate the ssh-public key file and paste it to 

the client machine 

so in this way we can create passwordless authentication for linux server.

or else we can chnage ssh configuration file 

vi /etc/ssh/sshd_config 

go to this file

we can go th

checking for existing ssh key file ..

generate the ssh key file and copy to the remote server 

and upload the public key using the ssh-copy-id command 

now login to the server without passwords

this is way its possible 

10).

How to  troubleshoot the ctrld error in linux os ? how to troubleshoot it this things ?

this is called filesystem maintance error 

so we have t check the filesystem 

we can execute the command like as the vi /etc/fstab

missing configuration in /etc/fstab file

wrong specification of filesystem mountoptions

failing mount points

unwanted chaarters in fstab file

for that reason ,

df -TH command 

next am executing the command like as the fdisk -l 

it will list out the partitions information in linux os ...

now am checking both things 

in this way i can get clear details whether which disk is mounted or not ..

next got o /etc/fstab file 

here am checking the entries 

here particularly we need to change the default to defaults 

Ans save close this file ...

next reboot the server in linux os 

11)..How to troubleshoot root login issue in linux os sever?

go to ssh config file

her permit root login option here .

here only we can allow or deny the user 

next method is ,

the user is in normal user definitely we need to assign the root access for this user

so go this file name called as the ,

vi /etc/sudoers file

visudo file

here only we can edit the provide the root access for this normal user ..