Arch Linux

I do not think it makes sense for `base` to have a hard dependency on `systemd-sysvcompat`. The old init systemd and service management has been replaced with systemd a long time ago.

To be clear: The proposal is not to remove `systemd-sysvcompat` entirely, but simply to make it an optional dependency instead of a hard one.

`systemd-sysvcompat` provides two things:

1. compatibility with `init` through a symlink to `/usr/lib/systemd/systemd`
2. compatibility with `halt`, `poweroff`, `reboot`, and `shutdown` through symlinks to `/usr/bin/systemctl`

Addressing those two features is relatively straightforward:

1. The init symlink is not needed if one sets the `init` kernel parameter (`init=/usr/lib/systemd/systemd`). This should be mentioned in the install instructions.
2. `systemctl` can just be used directly. We would need to update scripts that still use `halt`, `poweroff`, `reboot`, and `shutdown` directly, if there are any.

Users who wish to continue using the old commands have several easy migration paths:

* Users who upgrade an existing installation have to do nothing. By making the package an optional dependency, it would stay installed by default. One would have to explicitly remove it if desired.
* Users who install Arch after this change can choose one of several easy options:
1. Install `systemd-sysvcompat`, which would be easily discoverable if made an optional dependency.
2. Create aliases
3. Manually create symlinks