Linux admin useful commands

1. Check for server load using top command with following options:
Shift p CPU Usage,
Shift m Memory Usage
& check which process is taking load with the help of above two options.
Kill the responsible process using k option.
2. Check for the downloads using
# ps auxw | grep nobody | grep mp3 , jpeg, wmv, mpeg, rar
# ps auxw | grep gzip, backup, fixquota
Suspend the perticular account who is repeatedly downloading the above mentioned files.
3. Check for access & error logs for following options
# tail -f /etc/httpd/logs/access_log | grep 408, zip
# tail -f /etc/httpd/logs/error_log | grep 203
4. Check mail spamming with following commands.
#tail -f /var/log/exim_mainlog | grep sendmail, public_html, tmp
5. Login to WHM of the server and check apache, cpu/memory, mysql status & check for frozen mails in mail queue manager.
6. Check Mysql errors with
# mysqladmin processlist
check the users, command, time & information fields.
7. If you are making changes to httpd.conf then first run # httpd -configtest before restarting httpd to reduce the downtime.
8. Restart the perticular service causing load tomgo hihg with # /scripts/restartsrv_httpd, exim, mysql