Halt the VM automatically

config.scm

@@ -1,5 +1,6 @@
 (use-modules (gnu)
-             (gnu services shepherd))
+             (gnu services shepherd)
+             (gnu packages admin))
 
 (define my-service
   (shepherd-service-type
@@ -9,7 +10,9 @@
       (documentation "This command is executed when the GUIX system boots.")
       (provision '(my-stuff))
       (start #~(lambda ()
-                 (system "(read len < /dev/sdb; dd if=/dev/sdc bs=1 count=$len | sh) > /dev/tty1")))))))
+                 (system (string-append "(read len < /dev/sdb; head -c $len < /dev/sdc | sh -s "
+                                        #$shepherd
+                                        ") > /dev/tty1"))))))))
 
 (operating-system
  (bootloader

to-be-run-in-vm.sh

@@ -1,5 +1,12 @@
 #!/bin/sh
 
+if [ "$#" -ne 1 ]; then
+  echo "Usage: $0 shepherd"
+  echo "where shepherd is the path to shepherd in the GUIX store as"
+  echo "given by \`shepherd' from (use-modules (gnu packages admin))"
+  exit 1
+fi
+
 echo
 { read len_script; read len_tar; } < /dev/sdb
 pwd
@@ -9,3 +16,11 @@ sha1sum signing-key.pub
 
 guix archive --authorize < signing-key.pub
 guix archive --import < hello.nar
+
+# Wait for the control socket for shepherd to appear and halt the VM.
+(
+  while [ ! -e /var/run/shepherd/socket ]; do
+    sleep 1
+  done
+  "$1/sbin/halt"
+) &