auto updates: document systemd unit and timer
Fixes:
@@ -26,6 +26,12 @@ If an image ID was used, Podman would not know which image to check/pull anymore
Moreover, the systemd units are expected to be generated with `podman-generate-systemd --new`, or similar units that create new containers in order to run the updated images.
Systemd units that start and stop a container cannot run a new image.
+
+### Systemd Unit and Timer
+
+Podman ships with a `podman-auto-update.service` systemd unit. This unit is triggered daily at midnight by the `podman-auto-update.timer` systemd timer. The timer can be altered for custom time-based updates if desired. The unit can further be invoked by other systemd units (e.g., via the dependency tree) or manually via `systemctl start podman-auto-update.service`.
+
+
## OPTIONS
#### **--authfile**=*path*
