Encrypt backups using GPG

The image supports encrypting backups using GPG out of the box. In case a GPG_PASSPHRASE environment variable is set, the backup archive will be encrypted using the given key and saved as a .gpg file instead.

Assuming you have gpg installed, you can decrypt such a backup using (your OS will prompt for the passphrase before decryption can happen):

gpg -o backup.tar.gz -d backup.tar.gz.gpg