more DRBD wizardry, used in a botched ganeti install recovery

howto/drbd.md

@@ -94,6 +94,18 @@ Then delete it:
 
     drbdsetup del-minor 0
 
+If you get errors because the device is busy, see if you can see what
+is holding on to it `/sys/devices/virtual/block/drbd0/holders`, for
+example:
+
+    # ls -l /sys/devices/virtual/block/drbd3/holders/
+    total 0
+    lrwxrwxrwx 1 root root 0 Aug 26 16:03 dm-34 -> ../../dm-34
+
+Then that device map can be removed with:
+
+    # dmsetup remove dm-34
+
 ## Pager playbook
 
 ### Resyncing disks
@@ -128,7 +140,7 @@ above):
 
 Then you can "reactivate" the disks simply by telling ganeti:
 
-    $ ssh fsn-node-01.torproject.org gnt-instance activate-disks onionoo-frontend-01.torproject.org
+    ssh fsn-node-01.torproject.org gnt-instance activate-disks onionoo-frontend-01.torproject.org
 
 And then the disk will resync.