command not found:
If you are getting a message like this there is usually a simple solution to your problem. For example let's say you want to run the command [ ip ], and you get something like below:
bash: ip: command not found
Then do this:  [ whereis ip ], and then you should see this:
ip: /sbin/ip /usr/share/man/man7/ip.7.gz /usr/share/man/man8/ip.8.gz
Ok, now you know where the binary executable is. ( Don't confuse this with the .exe suffix or the .com suffix they don't apply here ).
Now type this:   [ /sbin/ip ], and you should get something like this:

Usage: ip [ OPTIONS ] OBJECT { COMMAND | help }
	where  OBJECT := { link | addr | route | rule | neigh | tunnel |
        maddr | mroute | monitor }
      	OPTIONS := { -V[ersion] | -s[tatistics] | -r[esolve] |
        -f[amily] { inet | inet6 | ipx | dnet | link } | -o[neline] }

This applies to any command you type that gives you the command not found message. What it is telling you is that there is no path from your directory to the executable filename you have typed.