Top 20 Linux Commands for System Administrator in Linux

Linux Commands for System Administrator

1. How to find kernel version?

uname -r

2. How to display filesize in human readable format (e.g. KB, MB etc.,)?

ls -lh

3. What is the Linux process priority levels?

19 (lowest) to –20 (highest)

4. How many characters can have filename ?

5. How to Shutdown the system after 10 minutes?

shutdown -h +10

6. what is the command to rebuild the initrd image ?

mkinitrd

7. How to gather sar output specific time for memory?

sar -s 02:00:00 -e 03:00:00 -r

8. What file lists the DNS servers a UNIX host uses ?

/etc/resolv.conf

9. What’s the default filesystem type on Redhat Linux 5?

ext3

10. What command can you use to review boot messages?

dmesg

11. which filet to set a kernel parameters on a Linux machine?

/etc/sysctl.conf

12. What is the configuration file for ports?

/etc/services

13. How to create a swap file in a data partition?

dd if=/dev/zero of= bs= count=

14. How to delete files older than 7days?

find /path/to/files* -mtime +7 -exec rm {} \;

15. How to check disk usage in human readable and sort by size?

du -sh * | sort

16. How to list the password and its related details an user?

chage -l username

17. How to set account expiry date for an user?

chage -E "2012-06-31" raja

18. How to disable password aging for an user account?

chage -m 0 -M 99999 -I -1 -E -1 madhu

19. How to check memory map of a given process id 5264?

pmap 5264

20. How to verify crontab entry for a specific user

crontab -u username -l