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 ?
255
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
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