The initrd units are described in the graphs in the bootup manpage,
so use that one for them.
[Unit]
Description=Cleaning Up and Shutting Down Daemons
+Documentation=man:bootup(7)
DefaultDependencies=no
AssertPathExists=/etc/initrd-release
OnFailure=emergency.target
[Unit]
Description=Mountpoints Configured in the Real Root
+Documentation=man:bootup(7)
AssertPathExists=/etc/initrd-release
DefaultDependencies=no
[Unit]
Description=Switch Root
+Documentation=man:bootup(7)
AssertPathExists=/etc/initrd-release
[Unit]
Description=Switch Root
+Documentation=man:bootup(7)
AssertPathExists=/etc/initrd-release
DefaultDependencies=no
Wants=initrd-switch-root.service
[Unit]
Description=Cleanup udev Database
+Documentation=man:bootup(7)
DefaultDependencies=no
AssertPathExists=/etc/initrd-release
Conflicts=systemd-udevd.service systemd-udev-trigger.service systemd-udev-settle.service
[Unit]
Description=Create List of Static Device Nodes
+Documentation=man:kmod(8)
DefaultDependencies=no
Before=sysinit.target systemd-tmpfiles-setup-dev-early.service
ConditionCapability=CAP_SYS_MODULE