Updating undercloud user’s ssh key

In order to update the ssh key for the user on the undercloud, a few steps must be done to ensure you do not lock yourself out of the overcloud nodes. When the undercloud is installed, an ssh key is created and added to Nova running on the undercloud for provisioning the overcloud nodes. This key is uploaded into Nova as the default keypair. To view the keypair run:

source stackrc
openstack keypair list

Process to rotate ssh key

The process to rotate the user key is as follows:

  1. Generate new key and do not replace the existing key. For example:

    ssh-keygen -t rsa -N '' -f ~/new_ssh_key
  2. Copy ssh key to all existing hosts for the heat-admin user:

    for HOST in $(openstack server list -f value -c Networks | sed -e 's/ctlplane=//'); do
        ssh-copy-id -i ~/new_ssh_key heat-admin@$HOST
  3. Update the Undercloud’s Nova default keypair:

    openstack keypair delete default
    openstack keypair create --public-key ~/new_ssh_key.pub default
  4. Backup old key and replace it with the new keys:

    mkdir ~/.ssh/old_keys
    mv ~/.ssh/id_rsa ~/.ssh/old_keys/id_rsa.backup-$(date +'%Y-%m-%d')
    mv ~/.ssh/id_rsa.pub ~/.ssh/old_keys/id_rsa.pub.backup-$(date +'%Y-%m-%d')
    mv ~/new_ssh_key ~/.ssh/id_rsa
    mv ~/new_ssh_key.pub ~/.ssh/id_rsa.pub
  5. Remove old key from the allowed hosts on the nodes.