SSH Goodies that might save your life

I always make a list of SSH commands for a specific purpose. For example I have lists named: SSH for setting up a LEMP, SSH for setting up WordPress, so on and so forth.

The good thing about having the list is you don’t have to always google about the commands and trial and error every time. You already know what commands will work for specific scenario and it’s reusable and even automatable.

12 Useful Commands To Check Your Server Health using PuTTY or similar SSH client

12 Useful Commands To Check Your Server Health using PuTTY or similar SSH client

The good thing about having the list is you don’t have to always google about the commands and trial and error every time…Read more

Here I am going to share all these SSH list that might save your life or at least make your life easier.

SSH to check if your server is overload/under attack

What would you do the first thing when your website is down and your server is in extremely high load? Would it be an attack? Or just some temporary spike?

Try:

Check your server load

top

Check the number of concurrent users

You can view the current concurrent users within SSH using:

netstat -plan | grep :80 | wc -l

Restart your server

Restart Nginx server:

service nginx restart

Or

service nginx reload

 

Restart Apache server:

/etc/init.d/apache2 restart
Or
sudo /etc/init.d/apache2 restart

Or

service apache2 restart

If your restarting your server doesn’t help, you might need to look into some logs and do further investigation.

Checkout what PHP script is running

ps -aux | grep php - see running php

Check if your server is busying sending emails

tail -f /var/log/exim_mainlog

Chances are high that your server hang because of sending out a large number of spam email. WordPress user always has this issue when they got unreliable plugins installed.

Check if the MySQL Database is busy

mysqladmin pr -p

Check if your server is generating large number of error log

tail -f /var/log/nginx/error.log

Please note that your error log directory may be different depends on your OS. If you happen to find your server is generating a large number of error log, look at the IP addresses that generating the error, if the IP addresses were the same, you are probably under attack attempts.

The hundreds of attack attempts generated by bot within a minute might is causing your server being busy. Ban these IP addresses can solve the problem temporary.

How to ban IP addresses

csf -d IP_ADDRESS
csf -r
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