Posts Tagged ‘root port’

How to configure ssh to automatically connect to non standard ssh port numbers (!port 22)

Tuesday, August 2nd, 2011

Reading Time: 2 minutesSSH Artistic Logo, don't give away your password

Today I’ve learned from a admin colleague, a handy tip.
I’m administrating some Linux servers which are configured on purpose not to run on the default ssh port number (22) and therefore each time I connect to a host I have to invoke the ssh command with -p PORT_NUMBER option.

This is not such a problem, however when one has to administrate a dozen of servers each of which is configured to listen for ssh connections on various port numbers, every now and then I had to check in my notes which was the correct ssh port number I’m supposed to connect to.

To get around this silly annoyance the ssh client has a feature, whether a number of ssh server hosts can be preconfigured from the ~/.ssh/config in order to later automatically recognize the port number to which the corresponding host will be connecting (whenever) using the ssh user@somehost without any -p argument specified.

In order to make the “auto detection” of the ssh port number, the ~/.ssh/config file should look something similar to:

hipo@noah:~$ cat ~/.ssh/config
Host home.*.pc-freak.net
User root
Port 2020
Host www.remotesystemadministration.com
User root
Port 1212
Host sub.pc-freak.net
User root
Port 2222
Host www.example-server-host.com
User root
Port 1234

The *.pc-freak.net specifies that all ssh-able subdomains belonging to my domain pc-freak.net should be by default sshed to port 2020

Now I can simply use:

hipo@noah:~$ ssh root@myhosts.com

And I can connect without bothering to remember port numbers or dig into an old notes.
Hope this ssh tip is helpful.