systemd network-pre dependencies for dhcpcd (possibly others)

[Mark Rogers]

In order for systemd units to request that they are started before networking, they should specificy Before=network-pre.target. However, dhcpcd does not honour that dependency. (There may be other network units that don't, this is the one that caught me out.)

The dhcpcd unit file should include
After=network-pre.target

From systemd.special man pages:

$ man 7 systemd.special
       [...]
       network-pre.target
           This passive target unit may be pulled in by services that want to
           run before any network is set up, for example for the purpose of
           setting up a firewall. All network management software orders
           itself after this target, but does not pull it in.

For more info see this thread on systemd-devel:
https://lists.freedesktop.org/archives/systemd-devel/2020-June/044812.html