document the new fabric installer

tsa/howto/new-machine-hetzner-robot.mdwn

@@ -232,6 +232,30 @@ which we'll use below.
 
         reboot
 
+Semi-automated install
+----------------------
+
+The above procedure was automated using [[Fabric]] in the `tsa-misc`
+git repository. This still remains to be documented better, but the
+magic commandline for fsn-node-05 was:
+
+    ./install -H root@88.99.194.57 --fingerprint 0d:4a:c0:85:c4:e1:fe:03:15:e0:99:fe:7d:cc:34:f7 --verbose hetzner-robot fsn-node-05.torproject.org installer/disk-config/gnt-fsn-NVMe installer/packages installer/post-scripts/
+
+Taking that apart:
+
+ * `-H root@88.99.194.57`: that's the IP address provided by Hetzner
+   in the confirmation email
+ * `--fingerprint`: the ed25519 fingerprint from the same email
+ * `hetzner-robot`: the install job type
+ * `fsn-node-05.torproject.org`: the hostname to set on the machine
+ * `installer/disk-config/gnt-fsn-NVMe`: the disk configuration
+ * `installer/packages`: the base packages to isntall
+ * `isntaller/post-scripts/`: post-install scripts
+ 
+The last two are passed to grml-debootstrap and should rarely be
+changed (although they could be coverted in to Fabric tasks
+themselves).
+
 Configuration
 -------------