Setup an SSH user on an existing VM

Create the user and setup the SSH key

$ scp ${PATH_TO_SSH_KEYS}id_rsa.pub existing-user@${MACHINE_IP_ADDRESS}:.
$ ssh existing-user@${MACHINE_IP_ADDRESS}
$ sudo su
# useradd -s /bin/bash -m my-new-username
# mkdir /home/my-new-username/.ssh
# cp id_rsa.pub /home/my-new-username/.ssh/
# touch /home/my-new-username/.ssh/authorized_keys
# cat id_rsa.pub >> /home/my-new-username/.ssh/authorized_keys
# rm id_rsa.pub
# chown -R my-new-username:my-new-username /home/my-new-username/.ssh
# chmod 700 /home/my-new-username/.ssh
# chmod 600 /home/my-new-username/.ssh/authorized_keys

Test the SSH connection: ssh my-new-username@${MACHINE_IP_ADDRESS} -i ${PATH_TO_SSH_KEYS}id_rsa

Make sure the ansible user is in the sudo group

$ groups my-new-username
my-new-username : my-new-username
$ sudo su
# usermod -aG sudo my-new-username

Then use visudo to make the ansible user able to work without password: my-new-username ALL = (ALL) NOPASSWD: ALL

Different approach

The VMs need to be aware of the SSL public key of the ansible user. This means adding it to their ~/.ssh/authorized_keys. This could be done either modifying that file or using a combination of:

ssh-keyscan ${REMOTE_VM_IP_ADDR} > ~/.ssh/knwon_hosts to retrieve the SSL public key of the remote VM
ssh-copy-id my-user-at-the-vm@${REMOTE_VM_IP_ADDR} to copy our own SSL public key to the remote VM ~/.ssh/authorized_keys file

tappoz/add-ssh-user-to-existing-linux-vm.md

Setup an SSH user on an existing VM

Different approach