--- layout: doc title: How to make any file in a TemplateBasedVM persistent using bind-dirs permalink: /doc/bind-dirs/ redirect_from: - /en/doc/bind-dirs/ --- # How to make any file in a TemplateBasedVM persistent using bind-dirs # ## What are bind-dirs? ## With [bind-dirs](https://github.com/QubesOS/qubes-core-agent-linux/blob/master/vm-systemd/bind-dirs.sh) any arbitrary files or folders can be made persistent in TemplateBasedVMs. ## What is it useful for? ## In a TemplateBasedVM all of the file system comes from the template except `/home`, `/usr/local`, and `/rw`. This means that changes in the rest of the filesystem are lost when the TemplateBasedVM is shutdown. bind-dirs provides a mechanism whereby files usually taken from the template can be persisted across reboots. For example, in Whonix, [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). In this way sys-whonix can benefit from the Tor anonymity feature 'persistent Tor entry guards' but does not have to be a StandaloneVM. ## How to use bind-dirs.sh? ## Inside your TemplateBasedVM. 1. Make sure folder `/rw/config/qubes-bind-dirs.d` exists. sudo mkdir -p /rw/config/qubes-bind-dirs.d 2. Create a file `/rw/config/qubes-bind-dirs.d/50_user.conf` with root rights inside a TemplateBasedVM. 3. Edit the file 50_user.conf to append a folder or file name to the `binds` variable. (In the following example we are using folder `/var/lib/tor`. You can replace that name with a folder or file name of your choice.) binds+=( '/var/lib/tor' ) Multiple entries are possible, each on a separate line. 4. Save. 5. Reboot the TemplateBasedVM. 6. Done. If you added for example folder `/var/lib/tor` to the `binds` variable, from now on any files within that folder will persist reboots. If you added for example file `/etc/tor/torrc` to the `binds` variable, from now on any modifications to that file will persist reboots. ## Other Configuration Folders ## * `/usr/lib/qubes-bind-dirs.d` (lowest priority, for packages) * `/etc/qubes-bind-dirs.d` (intermediate priority, for template wide configuration) * `/rw/config/qubes-bind-dirs.d` (highest priority, for per VM configuration) ## How does it work? ## bind-dirs.sh is called on startup of a TemplateBasedVM, and configuration files in the configuration folders above are parsed to build a bash array. Files or folders identified in the array are copied to /rw/bind-dirs if they do not already exist there, and are then bind mounted over the original files/folders. Creation of the file and folders in /rw/bind-dirs should be automatic the first time the TemplateBasedVM is restarted after configuration. If you want to circumvent this process, you can create the relevant filestructure under /rw/bind-dirs and make any changes at the same time that you perform the configuration, before reboot. ## Limitations ## * Files that exist in the TemplateVM root image cannot be deleted in the TemplateBasedVMs root image using bind-dirs.sh. * Re-running `sudo /usr/lib/qubes/bind-dirs.sh` without a 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. * Many editors create a temporary file and copy it over the original file. If you have bind mounted an individual file this will break the mount. Any changes you make will not survive a reboot. If you think it likely you will want to edit a file, then either include the parent directory in bind-dirs rather than the file, or perform the file operation on the file in /rw/bind-dirs. * Some files are altered when a qube boots - e.g. `/etc/hosts`. If you try to use bind-dirs on such files you may break your qube in unpredictable ways. You can add persistent rules to `/etc/hosts` file using script `/rw/config/rc.local` that is designed to override configuration in /etc, starting services and etc. For example, to make software inside some TemplateBasedVM resolving the domain `example.com` as `127.0.0.1` open `/rw/config/rc.local` inside this TemplateBasedVM and add: ~~~ echo '127.0.0.1 example.com' >> /etc/hosts ~~~ After every boot of the TemplateBasedVM `rc.local` script will add line `127.0.0.1 example.com` to `/etc/hosts` file and the software inside the TemplateBasedVM will resolve domain `example.com` accordingly. You cam add several rules to `/etc/hosts` the same way. ## How to remove binds from bind-dirs.sh? ## `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. `/rw/config/qubes-bind-dirs.d/50_user.conf` ~~~ binds=( "${binds[@]/'/var/lib/tor'}" ) ~~~ (Editing `/usr/lib/qubes-bind-dirs.d/40_qubes-whonix.conf` directly is strongly discouraged, since such changes get lost when that file is changed in the package on upgrades.) ## Discussion ## [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)