need systemd unit file.

The SystemD init system is universal in newer linux distributions, need to modernized init system support.

Using the init.d file currently there, px is started before all file systems are available. Proper integration into systemd, will allow us to delay startup until after the file systems are up.

Start by locating and reading the existing init.d file referenced in the issue, then inspect how px is launched and what filesystem readiness it requires. Done means adding a systemd unit that starts px after the filesystems are available and preserves the existing service behavior.

Written by the indexing model from the issue text.