Written by Peter Tasker Open source developer in Ottawa Ontario, Canada You should follow him on Twitter

August 20, 20151 min read

This is more an informational post for myself, but here’s some nifty commands that help debug what’s going wrong on a server when things aren’t going right.

netstat -t
netstat -tn

These are good for watching WHO is hitting your server and what their IP is. netstat -tn shows the unresolved address, so you should get the IP’s of possible spammers

Once you’ve got the IP(s) you can block them with iptables like so:

<pre class="bash">iptables -I INPUT -s <IP ADDRESS> -j DROP

Another good tool for watching network traffic is iftop. You’ll need to install this one via Yum or Apt though:

 iftop -N -i eth0

1__ssh

And for overall machine health, nothing beats good old htop! Ahh, CPU usage back to normal.

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