Back up of encrypted home dir of logged users impossible

[Milan Knizek]

Once the user logs in, the $HOME/.Private is replaced by decrypted files, effectively hiding the encrypted ones.

This seems to me as a design error. The .Private directory should be outside of user's home directory to allow for backup of a live system with users logged in (no matter that this is not recommended due to possible on-going changes to the file system).

Ubuntu 9.04 amd64. Affects adduser --encrypt-home and possibly ecryptfs-setup-private --all-home

[Dustin Kirkland  (kirkland)]

Actually, it is possible to get to your encrypted data!

Try this:

 $ umount.ecryptfs_private && cd $HOME/.Private && mount.ecryptfs_private

This should momentarily unmount your home (or private) directory, put you in your encrypted directory, and then remounted (as quickly as possible).

This is how I backup my encrypted data!

:-Dustin

[Milan Knizek (knizek)]

Interesting, I did not know that this is possible and it seems to work also with a running gnome session.

However, I wonder if the same can be done by a cron job to do the backup - I guess the cron job (run as root) does not have access to keyrings of the logged users (I have a multi-user environment). I'll try it later.

[Dustin Kirkland  (kirkland)]

Note that root could establish a bind mount of your .Private
directory, if he wished.

Perhaps do something like this:
 # mkdir /home/.$USER
 # mount -o bind /home/$USER/.Private /home/.$USER

:-Dustin

[Rafał Błaszczyk (rblaszczyk)]

Dustin - you cannot do that, user is logged in and the /home/$USER/.Private is not visible (it's overmounted). Your solution with unmounting is also not good enough - there is a good chance user is using some files and you cannot unmount.

There's an easier solution. You can mount /home in another directory using --bind option. The default behaviour of bind doesn't mount the submounts so you can easily access .Private dirs in home directories.

To do that I use /etc/fstab line:
/home /home-bind none ro,bind

now I have all home directories visible inf /home-bind as the user weren't logged in (they are not overmounted). Read-only - just enough for backup (you can make that rw for further restores).

[Dustin Kirkland  (kirkland)]

Rafał-

This is what I meant, when I wrote:
> Note that root could establish a bind mount of your .Private
> directory, if he wished.

I really like your solution, though. Bind-mounting all of /home
read-only is very elegant! This is something I might look into for
Karmic.

:-Dustin