motd: maintain a /etc/motd file with interesting info abot the TAC

Not anyone looks at the web interface or the display of the TAC.
This gives us a third vector to convey information to the user.

Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>

.gitignore

@@ -1,6 +1,8 @@
 /target
 /.cargo
 /demo_files/home/root/.ssh/authorized_keys
+/demo_files/etc/motd
+/demo_files/var/run/tacd/motd
 /web/npm-shrinkwrap.json
 /web/oe-logs
 /web/oe-workdir

src/main.rs

@@ -30,6 +30,7 @@ mod iobus;
 mod journal;
 mod led;
 mod measurement;
+mod motd;
 mod regulators;
 mod setup_mode;
 mod system;
@@ -128,6 +129,17 @@ async fn init(screenshooter: ScreenShooter) -> Result<(Ui, WatchedTasksBuilder)>
     // in the web interface.
     journal::serve(&mut http_server.server);
 
+    // Maintain a /etc/motd with useful information about the TAC
+    motd::keep_updated(
+        &mut wtb,
+        &dut_pwr,
+        &iobus,
+        &rauc,
+        &setup_mode,
+        &temperatures,
+        &usb_hub,
+    )?;
+
     // Set up the user interface for the hardware display on the TAC.
     // The different screens receive updates via the topics provided in
     // the UiResources struct.