Troubleshooting SSH Connections

A friend of mine asked me to troubleshoot a problem he was having with authenticating to an SSH server. Like most problems, the answer could be found buried in logs, or in this case, debug output. For those who use SSH and don’t know about -v, it time you learnt about this wonderful switch. In the UNIX world, -v usually denotes verbostiy, that is, the level of detail that the program will display. Most programs you run from the command line support -v, and often -vv and -vvv. The more v’s, the higher the level of verbosity.

Start up an SSH session from the command line:

ssh username@host -v
ssh username@host -vv
ssh username@host -vvv

If you aren’t using -v while troubleshooting, try it out, it will make your life a whole lot easier.