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| Redhat troubleshooting interview questions |
Redhat Linux troubleshooting interview questions
Name Some of the useful Linux troubleshooting commands
dmesg — It is used for Kernel Buffer
vmstat — It is used to check virtual memory.
pidstat — It is used to checks every PID status
mtr — It is used to checks network latency
mpstat — It is used to checks every CPU usages
iostat — It is used to checks disk status
free — checks memory status
ifconfig — It is used to checks network interfaces
SAR — It is used to check complete system activity
ss — It is used to Checks connection performance
iftop — It is used to Check network performance
smem — Checks memory allocated to per process
Which directory will hold the network configuration files?
ans- /etc/sysconfig/network.scripts
what are daemons are needed for SAMBA to handle its work?
ans- smb,nmb
what of the following configuration should be done to enable automounting on the client-side?
ans- autofs
How to check the IP address of the server?
Ans- commands like ifconfig, hostname -I,
How to check the default gateway of the server?
Ans- route -vn
What is ulimit?
Ans- Ulimit is a type of descriptor were how many files that user can open
#ulimit
Disk space is full even after deleting a file of 6GB?
Ans- first check df -Th and then lsof | grep deleted
now kill the process with process id kill -9 <process id>
How to ssh to your server?
Ans- ssh -i <pam file>
ssh -v -i <pam file>
What is the use of curl?
Ans - It is used to check the local webserver
#curl localhost
What is the use of the W command?
Ans- It is used for how many users are logged in and current load of the server, uptime of the server
How to kill all processes of any user?
Ans- pkill -9 -u `id -u username`
How to mount a disk permanently?
Ans-By using vim /etc/fstab you can mount disk by giving UUID and mount point.
#mount -a
How to check hidden files and how to create them?
Ans- ls -la you can check hidden files, and create a hidden file we
use #touch .file
How to start the process at startup time?
Ans- vim /etc/rc.local you can start any process
service httpd start
or you can use crontab -e
What does a nameless directory represent?
Ans- #ls -la
. it shows the current directory
.. it shows the previous working directory
How do you check for free disk space?
Ans- df -Th
df -ik It shows the inode value
How do you check open ports on Linux Servers?
Ans- netstat -tunlp
How do you check the process of CPU usage?
Ans- By using the top command by pressing P you can check CPU usage.
How do you deal with mounting partitions?
Ans- cat /proc/mounts
Or you can check with findmnt
How do you find the use of a command you don’t know?
Ans- whatis <command name>
How to check the ACL is on a file?
Ans- getfacl /path filename
What command do you use to check the attribute of a file?
Ans- lsattr /etc/fstab
chattr +i /etc/fstab it is used for creating attributes
What will happen if I remove execute permission from a directory?
Ans- mkdir /data
ls -l
now if you remove permission by using
chmod o-x /data
you cannot access the directory by any user
so you have to remove the permission by
chmod a-x /data to access files by any user.
How to check if OS is running on Virtual or Physical Machine?
Ans- demidecode | grep -i vm
How to change the owner, group of a file in Linux?
Ans- chown karan:karan /tmp/file
What is the use of the NMAP command?
Ans- It is used to check open port in remote server
Nmap -A 8.8.8.8
How to remove an INODE from the Linux File system?
Ans- First find the file by inode number by
ls -il
kill -9 <process id>