I recently created a new server at home and install Ubuntu 9.10 Server on it.   As a consequence all the SSH keys I used to access my old server were lost and I needed to add them back again….one at a time from each machine I use to access it.

Although this does not seem a big deal, the method I was using previously was as follows:-

cat ~/.ssh/id_rsa.pub | ssh <user>@<host>
'dd of=.ssh/authorized_keys oflag=append conv=notrunc'

Although this worked fine, I was catching up on my Linux reading and in Linux Journal #184 (August 2009) another reader Mark K. Zanfardino wrote in withe following more simplified command which works great on Ubuntu:-

ssh-copy-id -i ~/.ssh/id_rsa.pub <user>@<host>

This is not only easier to remember, it also checks that the key being added doesn’t already exist on the server! Brilliant!