Stupid SSH Tricks

I’m writing down these SSH configuration tweaks because I tend to change them infrequently enough that I forget them :-)

Configuring SSH keys

Sometimes it might be useful to use seperate SSH keys for seperate purposes. For example, one for work and one for peprsonal. On macOS this can be accomplished using ~/.ssh/config

For each host that you want to use a specific key for, you can create an entry like this :

Host gitlab.home
	Hostname 192.168.1.50
	IdentityFile ~/.ssh/home_rsa

The Host line gives a user freindly name, the Hostname line specifies the IP address or DNS name of the desired host. Lastly the IdentityFile line specifies the path to the ssh key to use for authentication.

Disabling Host Verification

Use cauton with this one… In my case I need to ssh into lab computers for maintenance purposes. These systems are on DHCP and may get new IP addresses at times. Having to modify the known_hosts file everytime this happened was a bit of a pain. To diasble host verification I added the following to ~/.ssh/config

Host *
	StrictHostKeyChecking no
	UserKnownHostsFile=/dev/nul

This completely disables host checking.