Backing up with rsync to a bitlocker disk mounted under Ubuntu on Raspberry Pi

Needed to set up backup to a bitlocker drive (corp policy - not allowed to put anything on a driver that's not bitlocker'd).  Corp laptops are set up such that they want to inspect all data written to external devices, so backups ended up being painfully slow (especially when jar files were involved since it wanted to unzip them and scan everything in them).  Decided to go with rsync over ssh from cygwin bash shell.

For fun (and since I didnt want this stuff on my personal machines), I decided to buy a Raspberry Pi and use that as my rsync target with the bitlocker disk mounted using dislocker.

I think I start out trying to install a packaged version with apt-get, but had dependency problems (might have had something to do with trying to run under Ubuntu on Raspberry Pi) , so reverted to these instructions: http://blog.airbuscybersecurity.com/post/2016/01/Mounting-Bitlocker-Volumes-Under-Linux

On the server side, I ended up with two scripts:

vmdiskmount:

dislocker-fuse -V /dev/sda1 -u -- /mnt/dislocker
mount -t ntfs-3g -o loop /mnt/dislocker/dislocker-file /mnt/vmdisk
mount | grep vmdisk

vmdiskumount:

umount /mnt/vmdisk && umount /mnt/dislocker
mount | grep dislocker

The mount script will prompt you for your bitlocker passphrase.  Note that shutting down the server without unmounting dislocker first can supposedly cause scary things to happen with the bitlocker encryption.

I also setup usermapping to map between windows SIDs and my linux user/group.  This goes in /mnt/vmdisk/.NTFS-3G/UserMapping:

# User mapping proposal :# -------------------- cut here -------------------1001::S-1-5-21-4271255075-229453548-3213529333-6405:1001:S-1-5-21-4271255075-229453548-3213529333-513::S-1-5-21-4271255075-229453548-3213529333-10000# -------------------- cut here -------------------

On the client side, its just standard rsync commands to send the data. Again, corp security required more dancing - cygwin needed to run as admin, but you cant do that directly anymore, so you have to run a DOS window as admin and launch cygwin from there. Also, trying to rsync the c drive doesnt work well because only the trusted installer user has write privs, so rysnc gets locked out as soon as it syncs the root directory on c: (which is the first thing it does).  Trick is to specify directories under c: as the rsync sources rather than the c drive itself.