polish and add

README.md

@@ -2,7 +2,12 @@
 mounts an overlay filesystem over the root filesystem
 
 I use this for my Raspberry Pi, but it should work on any Debian or derivative.
-It uses initramfs. Stock Raspbian doesn't use one so step one would be to get initramfs working. Something like:
+
+The root file system on the sd-card is mounted read-only on /overlay/lower, and / is a
+read-write copy on write overlay.
+
+It uses initramfs. Stock Raspbian doesn't use one so step one would be to get initramfs working. 
+Something like:
 
 ```bash
 sudo mkinitramfs -o /boot/init.gz
@@ -42,17 +47,39 @@ if [ ! -z "${IMCHROOTED}" ]; then
         PS1="chroot(${IMCHROOTED})\w:# "
 fi
 ```
-I use rootwork to work on the real root filesystem. 
-I put it in ~/bin and add ~/bin to my path
-
-After rebooting, the root filesystem should be an overlay. If it's on tmpfs any changes made will be lost after a reboot. If you want to upgrade packages, for example, run `rootwork`, the prompt should change to
 
+After rebooting, the root filesystem should be an overlay. If it's on tmpfs any changes 
+made will be lost after a reboot. If you want to upgrade packages, for example,
+run `rootwork`, the prompt should change to
 ```bash
 chroot(/overlay/lower)/:#
 ```
-You're now making changes to the sdcard, and changes will be permanent. 
 
-After you've finished working on the sdcard run `exit`. rootwork tries to clean up by umounting all the mounts it mounted, but often it can't umount a filesystem due to a lock file or something else causing the filesystem to be busy. It's probably a good idea to reboot now for 2 reasons, 1 to clear the mounts that couldn't be umounted, and also to test it still boots ok after the changes you've just made. 
+You're now making changes to the sdcard, and changes will be permanent.
+
+I use `rootwork` to work on the real root filesystem.
+I put it in ~/bin and add ~/bin to my path.
+
+The /run directory is problematic to umount, so atm `rootwork` --rbind mounts it
+on the sd-card root file system, /overlay/lower, and it isn't umounted like /boot 
+/proc /sys and /dev are.
+
+After you've finished working on the sd-card run `exit`. `rootwork` tries to clean up 
+by umounting all the mounts it mounted and remount /overlay/lower read-only, but 
+often it can't due to an open file or something else causing the filesystem to be busy.
+It's probably a good idea to reboot now for 2 reasons:
+
+- leaving /overlay/lower read-write could cause file corruption on power loss. 
+- to test it still boots ok after the changes you've just made.
+
+Whenever the kernel is updated you need to rerun 
+
+```bash
+sudo mkinitramfs -o /boot/init.gz
+```
+
+TODO: see if there's a hook to automatically run `sudo mkinitramfs -o /boot/init.gz` 
+on kernel install
 
 There are comments in some of the files you might want to read
 and that's about it.