For example, it is useful for Whonix, sys-whonix, where [Tor's data dir /var/lib/tor has been made persistent in the TemplateBased ProxyVM sys-whonix](https://github.com/Whonix/qubes-whonix/blob/8438d13d75822e9ea800b9eb6024063f476636ff/usr/lib/qubes-bind-dirs.d/40_qubes-whonix.conf#L5). So sys-whonix does not require to be a StandaloneVM. And therefore can benefit from the Tor anonymity feature 'persistent Tor entry guards' without the overhead of a StandaloneVM.
2. Create a file `/rw/config/qubes-bind-dirs.d/50_user.conf` with root rights inside a VM.
3. Append a folder or file to the `binds` variable. In the following example we are using folder `/var/lib/tor`. You can replace that folder with a folder or file of your choice.
* Does not work if the file / folder in question does not already exist in the root image. I.e. a file that does not exist in the root image cannot be bind mounted in the TemplateBasedVM.
* Re-running `sudo /usr/lib/qubes/bind-dirs.sh` without previous `sudo /usr/lib/qubes/bind-dirs.sh umount` does not work.
* Running 'sudo /usr/lib/qubes/bind-dirs.sh umount' after boot (before shutdown) is probably not sane and nothing can be done about that.
`binds` is actually just a bash variable (an array) and the bind-dirs.sh configuration folders are `source`d as bash snippets in lexical order. Therefore if you wanted to remove an existing entry from the `binds` array, you could do that by using a lexically higher configuration file. For example, if you wanted to make `/var/lib/tor` non-persistant in `sys-whonix` without manually editing [`/usr/lib/qubes-bind-dirs.d/40_qubes-whonix.conf`](https://github.com/Whonix/qubes-whonix/blob/master/usr/lib/qubes-bind-dirs.d/40_qubes-whonix.conf), you could use the following.
(Editing `/usr/lib/qubes-bind-dirs.d/40_qubes-whonix.conf` directly is recommended against, since such changes get lost when that file is changed in the package on upgrades.)
[TemplateBasedVMs: make selected files and folders located in the root image persistent- review bind-dirs.sh](https://groups.google.com/forum/#!topic/qubes-devel/tcYQ4eV-XX4/discussion)