By some sheer coincidence, I searched this topic today. I’ve been a consistent user of the parenthesis expansion, but never thought of why I preferred one or the other.

I suppose the primary advantage is that $() will expand in a consistent way. You can even nest quotes and more expansions in one, while you’d struggle the same with backtick notation.

So I’ll just keep using parentheses.

In addition to podman unshare (which you would just prefix in front of commands like chmod), you can just temporarily do podman unshare chown -R root: <path> if you backup while the container is down. Don’t try that command on live containers.

For a more permanent solution, you can investigate which user (ID) is the default in the container and add the option --user-ns=“keep-id:uid=$the_user_id”. This does not work with all images, especially those that use multiple users per container, but if it works, the bind mount will have the same owner as the host.

To find the user ID, you can run podman exec <container> id. In most of the images I use, it’s usually 1000.