poky/meta/files/overlayfs-all-overlays.service.in

[Unit]
Description=Groups all overlays required by {PN} in one unit
After={ALL_OVERLAYFS_UNITS}
Requires={ALL_OVERLAYFS_UNITS}

[Service]
Type=oneshot
ExecStart=/bin/true
RemainAfterExit=true

[Install]
WantedBy=local-fs.target