Bug 1403313

Documentation:  https://access.redhat.com/documentation/en/red-hat-openstack-platform/9/single/director-installation-and-usage/#sect-Migrating_VMs_from_an_Overcloud_Compute_Node

The documentation in the link says:
 Log into each Compute node as the nova user and run the following script to set up the keys:

NOVA_SSH=/var/lib/nova/.ssh
mkdir ${NOVA_SSH}

cp nova_id_rsa ${NOVA_SSH}/id_rsa
chmod 600 ${NOVA_SSH}/id_rsa
cp nova_id_rsa.pub ${NOVA_SSH}/id_rsa.pub
cp nova_id_rsa.pub ${NOVA_SSH}/authorized_keys

chown -R nova.nova ${NOVA_SSH}

# enable login for nova user on compute hosts:
usermod -s /bin/bash nova

# add ssh keys of overcloud nodes into known hosts:
ssh-keyscan -t rsa `os-apply-config --key hosts --type raw --key-default '' | awk '{print $1}'` >> /etc/ssh/ssh_known_hosts



But running usermod and appending lines to /etc/ssh/ssh_known_hosts requires root (or explicit permissions)

./migrat_prep.sh: line 13: /usr/sbin/usermod: Permission denied
Traceback (most recent call last):
  File "/bin/os-apply-config", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/os_apply_config/apply_config.py", line 335, in main
    opts.metadata = load_list_from_json(opts.os_config_files)
  File "/usr/lib/python2.7/site-packages/os_apply_config/apply_config.py", line 318, in load_list_from_json
    with open(json_file) as ocf:
IOError: [Errno 13] Permission denied: '/var/lib/os-collect-config/os_config_files.json'
./migrat_prep.sh: line 16: /etc/ssh/ssh_known_hosts: Permission denied


Thanks.