How to undo an ssh-copy-id?

I have a 2 node hadoop cluster.

I ran this command on the master:

$ssh-copy-id -i /home/hadoop/.ssh/id_rsa.pub [email protected]

How can I undo this? I would actually like to reassign the key.

192.168.1.1 is the slave.

Identify the public key that you copied when you ran ssh-copy-id:

cat ~/.ssh/id_rsa.pub

SSH to the server you copied the key to:

ssh [email protected]

Edit the file ~hadoop/.ssh/authorized_keys on 192.168.1.1 using your preferred editor, and delete the line containing your key.

If you have done a ssh-copy-id like:

remote='user@machine'
ssh-copy-id -i $remote

So you can access this remote machine without using a password:

ssh $remote

To undo it programmatically, you can script something like:

idssh=$(awk '{print $2}' ~/.ssh/id_rsa.pub)
ssh $remote "sed -i '\#$idssh#d' .ssh/authorized_keys"

I use it in scripts I need to scp several files, so I ask only once for password.