NixOS as LXC Container for ProtonMail Bridge

Tested on/with:

Connection to the NixOS instance

[root@Xperia10III defaultuser]# lxc-attach -n Bridge

Configuration files you need to create or edit

The editor is nano - you do not need that for long, in the configuration files you can get more editors, here vim will be installed.

[root@nixos:/]# ls -al -R /etc/nixos
total 24
drwxr-xr-x  3 root root 4096 Jan  1 22:34 .
drwxr-xr-x 17 root root 4096 Jan  5 06:34 ..
-rw-r--r--  1 root root 1104 Jan  1 22:34 configuration.nix
-rw-r--r--  1 root root  126 Dec 29 22:07 lxd.nix
-rw-r--r--  1 root root  693 Dec 31 22:42 protonmail-bridge_service.nix
drwxr-xr-x  2 root root 4096 Jan  1 22:46 scripts

total 12
drwxr-xr-x 2 root root 4096 Jan  1 22:46 .
drwxr-xr-x 3 root root 4096 Jan  1 22:34 ..
-rwxr--r-- 1 root root  813 Jan  1 22:46

Note that execution bit for the (chmod 744 when you are at that point) - otherwise the automatic start as service would not work. You need to create the scripts directory and the script in it.

Other files you need to create are lxd.nix and protonmail-bridge_service.nix


[root@nixos:/etc/nixos]# cat configuration.nix
# Edit this configuration file to define what should be installed on
# your system.  Help is available in the configuration.nix(5) man page
# and in the NixOS manual (accessible by running ‘nixos-help’).

{ config, pkgs, lib, modulesPath, ... }:


  imports =
      # Include the default lxd configuration.
      # Include the container-specific autogenerated configuration.

  environment.systemPackages = with pkgs; [
    # Define a package for the Proton Bridge service script
    (pkgs.writeShellScriptBin "protonmailBridgeScript" (builtins.readFile /etc/nixos/scripts/

  networking.useDHCP = false;
  networking.interfaces.eth0.useDHCP = true;
  networking.firewall.enable = false;
  services.openssh.enable = false;
  services.dbus.enable = true;

  services.protonmailBridge.enable = true;

  system.stateVersion = "23.11"; # Did you read the comment?

You can see that we want to install vim, binutils, protonmail-bridge (of course), gnupg, pinentry-curses, pass and screen. Of these, the introduction article explains the usage of GPG for the user authentication and the usage of screen-package to allow to run the CLI-type of ProtonMail Bridge as a service.

The version above is a stable version 23.11 of NixOS - you can pick yours if you do not like this one from


[root@nixos:/etc/nixos]# cat lxd.nix
{ config, pkgs, ... }:

  # Configuration related to LXC containers
  nix.settings.sandbox = false; # Disable sandboxing



[root@nixos:/etc/nixos]# cat protonmail-bridge_service.nix
{ config, pkgs, lib, ... }:

  cfg =;
{ = {
    enable = lib.mkEnableOption "ProtonMail Bridge";

  config = lib.mkIf cfg.enable { = {
      description = "ProtonMail Bridge";
      after = [ "" ];
      wantedBy = [ "" ];

      serviceConfig = {
        Type = "forking";
        ExecStart = "/run/current-system/sw/bin/protonmailBridgeScript start";
        ExecStop = "/run/current-system/sw/bin/protonmailBridgeScript stop";
        User = "root";  # It's better to use a non-root user
        Restart = "always";

[root@nixos:/etc/nixos/scripts]# cat

export HOME=/root
export PATH=${PATH}:/root/.nix-profile/bin
case "$1" in
    # will create an screen in detached mode (background) with name "protonmail"
    screen -S protonmail -dm protonmail-bridge --cli
    echo "Service started."
    # ignore this block unless you understand how screen works and that only lists the current user's screens
    result=$(screen -list | grep protonmail)
    if [ $? == 0 ]; then
      echo "Protonmail bridge service is ON."
      echo "Protonmail bridge service is OFF."
    # Will quit a screen called "protonmail" and therefore terminate the running protonmail-bridge process
    screen -S protonmail -X quit
    echo "Service stopped."
    echo "Unknown command: $1"
    exit 1

All Set - let's remove NixOS ! (not quite) ...

nix-channel --remove nixos

... to install the one above

nix-channel --add nixos
nix-channel --update
nixos-rebuild switch

How to install or update programs 

The below programs should come by the rebuild. If you wonder how they would get otherwise installed or how you can update them at a later date, this is the syntax:

nix-env -iA nixos.protonmail-bridge
nix-env -iA nixos.gnupg
nix-env -iA nixos.pinentry-curses
nix-env -iA nixos.pass
nix-env -iA nixos.screen

But there is normally no reason for that anymore, but you may like emacs -nw more than vim declared above for installation ...

If you arer reading this for updating the protonmail-bridge software version at a later date, please stop the protonmailBridge service before doing that using the systemctl commands explained below.

Test protonmail-bridge CLI manually

The main page of this book will explain you how (see Step 4). But before you go, do not forget to add this line in ~/.gnupg/gpg-agent.conf:

[root@nixos:~/.gnupg]# cat gpg-agent.conf
pinentry-program /root/.nix-profile/bin/pinentry-curses

If the file does not exist, create it.

Test as system service

The idea is, of course to make the container to work as daemon which you can start and stop to provide ProtonMail Bridge as service for your SFOS native email client or other (see the main page of this book Step 4b).

If you have any protonmail-bridge CLI sessions running, quit them now.

[root@nixos:/]# systemctl start protonmailBridge

[root@nixos:/]# systemctl status protonmailBridge
● protonmailBridge.service - ProtonMail Bridge
     Loaded: loaded (/etc/systemd/system/protonmailBridge.service; enabled; preset: enabled)
    Drop-In: /nix/store/y5fajbjj3czy2rcqvijkx0s8faf0cgdr-system-units/service.d
     Active: active (running) since Fri 2024-01-05 23:02:57 UTC; 57s ago
    Process: 270 ExecStart=/run/current-system/sw/bin/protonmailBridgeScript start (code=ex>
   Main PID: 273 (screen)
         IP: 0B in, 0B out
     Memory: 28.4M
        CPU: 750ms
     CGroup: /system.slice/protonmailBridge.service
             ├─273 SCREEN -S protonmail -dm protonmail-bridge --cli
             ├─275 protonmail-bridge --cli
             ├─308 keyboxd --homedir /root/.gnupg --daemon
             ├─320 gpg-agent --homedir /root/.gnupg --use-standard-socket --daemon
           └─322 scdaemon --multi-server

Jan 05 23:02:57 nixos systemd[1]: Starting ProtonMail Bridge...
Jan 05 23:02:57 nixos protonmailBridgeScript[270]: Service started.
Jan 05 23:02:57 nixos systemd[1]: Started ProtonMail Bridge.
lines 1-20/20 (END)

Other ways to check

[root@nixos:/]# screen -list
There is a screen on:
        273.protonmail  (Detached)
1 Socket in /tmp/screens/S-root.

How to join the protonMailBridge service

This is useful if there is a missing network connection, or if your credentials do not work, you can join the protonmail-bridge CLI to see its messages by writing:

[root@nixos:/]# screen -r protonmail

Other debugging commands for a failed service

This is quite useful to find the missing executables (or file without execution rights - see above for the script):

[root@nixos:/]# journalctl -u protonmailBridge.service --no-pager -n 50

If something is missing to run the script, it is perhaps easiest to find the missing command's location (always the linked one in NixOS, not the actual file with cryptic and random directory name) using which command and then add that in the PATH environment variable of the script.

Scripting in the SFOS side

Forget all the "user state LXC containers" and all that - since the prerequisite is that you can be devel-su, you can use sudo, right?


I have a script which knocks out the SFOS phone for the night and makes it brain dead, or almost. Well, I do not want the newly established ProtonMail Bridge "service" to run without networks or anything, so I stop the LXC container. In the morning I do the inverse (with Situations):

[defaultuser@Xperia10III situations]$ cat
sudo /usr/bin/systemctl stop wpa_supplicant >/tmp/stop-wpa_supplicant-root.log 2>/tmp/stop-wpa_supplicant-root.err
sudo /usr/bin/systemctl stop bluetooth >/tmp/stop-bt2-root.log 2>/tmp/stop-bt2-root.err
sudo /usr/bin/systemctl stop ofono >/tmp/stop-ofono-root.log 2>/tmp/stop-ofono-root.err
sudo /usr/bin/systemctl stop connman >/tmp/stop-connman-root.log 2>/tmp/stop-connman-root.err # No reason to keep e-mail Bridge running over the night, be quiet, too!
sudo /usr/bin/lxc-stop -n Bridge >/tmp/bridgestop.log 2>/tmp/bridgestop.err
/usr/bin/systemctl --user stop pulseaudio.service >/tmp/pulseaudiostop.log 2>/tmp/pulseaudiostop.err
sleep 5 # # Make your alarm clock sure to make some noise in the morning
/usr/bin/systemctl --user start pulseaudio.service >/tmp/pulseaudiostart.log 2>/tmp/pulseaudiostart.err

Revision #5
Created 5 January 2024 22:17:55 by canne
Updated 5 February 2024 15:16:21 by canne