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Auto installation of ssh public keys

Over the past few months, I’ve been writing little shell scripts here and there that make it just a bit easier to get my day to day work done. I thought I would post one of them here in case it might be beneficial to others as well.

I work a daily job where I am constantly using ssh to access many different remote machines all across the world. Since different machines can have different passwords and the like, I prefer to use public key authentication when possible to avoid this headache. The issue is, for each new machine I access, I used to have to manually install my pubkey on it to use public key authentication in the future. Even though Ubuntu has a shell script that ships with it called ssh-copy-id which handles the work for me, I knew that I could do better. Here is what I came up with:


#!/bin/bash -x

/usr/bin/ssh -o PreferredAuthentications=publickey -o PasswordAuthentication=no -n $@ &> /dev/null
if [ $? -ne 0 ] 
    ssh-copy-id $@
exec /usr/bin/ssh $@

What this script does is first check if my pubkey is installed on the remote machine. If not, it runs the ssh-copy-id script to install it. This will prompt for the password, then install my public key. After that, a normal ssh session is started which, if everything worked properly, will use pubkey authentication to log me in. Perfect! The exec was necessary so that konsole (my preferred terminal) would realize I was in a remote session and update the tab label properly. I also had to change the shell script /usr/local/bin/ssh-copy-id near the end to have it use /usr/bin/ssh rather than just “ssh” otherwise it would recursively infinitely loop.