syntax of the argument this takes depends on the distribution used,
and is either a numeric string (in case of Fedora Linux, CentOS, …,
e.g. `29`), or a distribution version name (in case of Debian,
- Ubuntu, …, e.g. `artful`). If neither this option, nor
- `Distribution=` is specified, defaults to the distribution version
- of the host. If the distribution is specified, defaults to a recent
- version of it.
+ Ubuntu, …, e.g. `artful`). Defaults to a recent version of the
+ chosen distribution.
`Mirror=`, `--mirror=`, `-m`