add pre-build checklist in cymru installer

howto/new-machine-cymru.md

@@ -132,8 +132,14 @@ Phew! Now you have a shell you can use to bootstrap your installer.
 
 ## Automated install procedure
 
-WARNING: this is a copy-paste of the [hetzner robot setup
-procedure](new-machine-hetzner-robot), it will not work as is!
+To install a new machine in the Cymru cluster, you first need to:
+
+ 1. configure the BIOS to display in the serial console (see [Serial console access](#serial-console-access))
+ 2. get [SSH access to the RACDM](#ssh-racdm-access)
+ 3. change the [admin iDRAC password](#idrac-password-reset)
+ 4. [bootstrap the installer](#bootstrapping-installer) through the virtual console and
+    (optionally, because it's easier to copy-paste and debug) through
+    the serial console
 
 From there on, the machine can be bootstrapped with a basic Debian
 installer with the [howto/Fabric](howto/Fabric) code in the `tsa-misc` git