When ~/.ssh is mounted from the host oskar user into a container that
runs as root, OpenSSH rejects ~/.ssh/config with 'Bad owner or
permissions' because the file UID doesn't match the running process.
Add -F /dev/null to the rsync SSH command to skip the config file
entirely. Also add UserKnownHostsFile=/dev/null so no known_hosts
write is attempted into a potentially read-only mounted .ssh dir.
The key itself (/root/.ssh/id_rsa) is still read as an implicit
default identity and is not affected by -F.
Reproduces on chelsty-infra (has ~/.ssh/config); safe for all nodes.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>