What to do when load on a Linux based web server goes high?

1) We must know about uptime command. If your website is loading slow, login into your web server console and run uptime to know load on your server.

>> uptime

If uptime shows high numbers like 100 or above 100, you must do something immediately, otherwise load might keep on increasing and will the server down.

3) Run following command to login as super user.

>> sudo su



4) Go to www directory

>> cd /var/www/html

5) If load is too high (Server is about to die), disable index.php (This will make your page inaccessible for a moment, but will decrease load as there won’t be new requests.

>> chmod 000 index.php

6) Check the top load causing IPs. Many times people run scripts to download content or to get malicious access. The below command (On Centos) tells you top 1000 visiting IPs.

>> tail -1000 /var/log/httpd/access_log | awk ‘{print $1}’ | sort | uniq -c |sort -n

A similar command for Ubuntu is

>> tail -1000 /var/log/apache2/access.log | awk ‘{print $1}’ | sort | uniq -c |sort -n

7) create a backup of .htaccess file

>> cp .htaccess back.htaccess



8) Block IP addresses in .htaccess if you find some particular IPs hitting your server

>> vim .htaccess

9) Monitor server load

>> watch -n 2 uptime

10) If you did not find any IP causing problems, you might want to check disk space and free memory.

Check available disk space

>> df -h

Check free memory

>> free -m

11) If none of the above steps help, then something might be wrong in your server code. Last but not least, check processes running on your server and try to debug it.

>> ps aux

Please make sure that you are not running heavy code (plugins) on every page load request. Do a lot of caching to avoid frequent DB or Network connections on a page request.

If nothing helps, then your page might have become popular and you need to upgrade your hosting plan.



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