How to set SSH config to grab part of ssh hostname and use as variable?

Question

I'm SSH'ing into multiple datacenters that are setup identically. Each datacenter has a jumpbox, and behind that there's access to various db servers etc.

It's a pain to manually specify entries for all these servers, when they're almost identical across datacenters, other than the jumpbox IP. So I'd like to set my .ssh/config file so that I can type datacenter_name-server_behind_jumpbox and have SSH grab the datacenter_name off the front of the host (so that I can re-use it in the ProxyCommand.

For example, if I want to access the Maria server in datacenter1, I'd create an SSH entry for the jumpbox called datacenter1. Then for the Maria server behind it, I'd setup something like:

Host %dc%-maria Hostname maria User jeff ProxyCommand ssh -q -W %h:%p %dc 

That way I only need to setup a single entry for each type of server that's located behind the jumpbox, and it automatically knows which datacenter jumpbox to hit.

Is something like this possible?

Answer 1

I add a fake suffix to the hostname with different proxy hosts

Host *.dc1 ProxyCommand ssh -q %r@dc1 -W %h:%p Host *.dc2 ProxyCommand ssh -q %r@dc2 -W %h:%p 

Then do something like ssh server1.dc1 and it will use the proxy host.

You can add Host entries for custom settings like this:

Host server1.* User jeff 

Answer 2

I'm in a similar situation and doing something like this:

# configuration for the datacenter, can add entries for each datacenter Host datacenter_name HostName <datacenter_ip> User <datacenter_user> IdentityFile <datacenter_keyfile> # usage match: datacenter_name-server_behind_jumpbox Host *-* User <server_behind_jumpbox user> IdentityFile <server_behind_jumpbox keyfile> Port <server_behind_jumpbox port> ProxyCommand ssh $(echo %h | cut -d- -f1) nc $(echo %h | cut -d- -f2) %p" 

Of course you could also do something more like you described

# usage match: datacenter_name-maria, specify one for each server Host *-maria User <maria user> IdentityFile <maria keyfile> Port <maria port> ProxyCommand ssh $(echo %h | cut -d- -f1) nc $(echo %h | cut -d- -f2) %p" 

Answer 3

You can run a script as a custom ProxyCommand and do your works before the real ProxyCommand:

.ssh/config:

Host *-maria Hostname maria User jeff ProxyCommand /bin/datacenter_ssh.sh %h %p 

datacenter_ssh.sh:

#!/bin/bash COMBINED=$1 DATACENTER=$(echo $COMBINED | cut -d'-' -f1) SERVER=$(echo $COMBINED | cut -d'-' -f2) PORT=$2 ssh -q -W $SERVER:$PORT $DATACENTER