nix/os/devices: add relabel command

After bytewise-copying from a prevoius disk, the partition labels and
logical volume groupnames need to be renamed according to the new disk
id.

nix/os/devices/disk.nix

@@ -5,6 +5,7 @@
 , moreargs
 , diskId
 , gitRoot
+, previousDiskId ? ""
 }:
 
 let
@@ -117,4 +118,50 @@ in rec {
 
     ${diskUmount}
   '';
+
+  diskRelabel = pkgs.writeScript "script" ''
+    #!/usr/bin/env bash
+    set -xe
+
+    read -p "Continue to relabel ${ownLib.disk.bootGrubDevice diskId} (YES/n)?" choice
+    case "$choice" in
+      YES ) echo "Continuing in 3 seconds..."; sleep 3;;
+      n|N ) echo "Exiting..."; exit 0;;
+      * ) echo "Exiting..."; exit 1;;
+    esac
+
+    sync
+    {
+    sudo fdisk ${ownLib.disk.bootGrubDevice diskId} <<EOF
+    x
+    n
+    2
+    2-${diskId}
+    n
+    3
+    3-${diskId}
+    r
+    i
+    2
+    i
+    3
+    w
+    EOF
+    } || {
+      sync
+      sudo partprobe  ${ownLib.disk.bootGrubDevice diskId}
+    }
+
+
+    if test "${previousDiskId}"; then
+      sudo cryptsetup luksOpen ${ownLib.disk.bootLuksDevice diskId} ${ownLib.disk.luksName diskId}
+      sync
+      sleep 1
+      if sudo vgs ${previousDiskId}; then
+        sudo vgrename ${previousDiskId} ${diskId}
+        sudo vgscan
+      fi
+    fi
+    sudo cryptsetup close ${ownLib.disk.luksName diskId}
+  '';
 }