Add install command

README.md

@@ -34,6 +34,16 @@ chmod +x jlmkr.py
 
 The `jlmkr.py` script (and the jails + config it creates) are now stored on the `jailmaker` dataset and will survive updates of TrueNAS SCALE.
 
+## Install Jailmaker Dependencies
+
+Unfortunately since version 22.12.3 TrueNAS SCALE no longer includes systemd-nspawn. In order to use jailmaker, we need to first install systemd-nspawn using the command below.
+
+```shell
+./jlmkr.py install
+```
+
+We need to do this again after each update of TrueNAS SCALE. So it is recommended to schedule this command as Post Init Script (see [Autostart Jail on Boot](#autostart-jail-on-boot)).
+
 ## Create Jail
 
 Creating a jail is interactive. You'll be presented with questions which guide you through the process.
@@ -46,7 +56,7 @@ After answering a few questions you should have your first jail up and running!
 
 ### Autostart Jail on Boot
 
-In order to start a jail automatically after TrueNAS boots, run `/mnt/mypool/jailmaker/jlmkr.py start myjail` as Post Init Script with Type `Command` from the TrueNAS web interface.
+In order to start a jail automatically after TrueNAS boots, run `/mnt/mypool/jailmaker/jlmkr.py start myjail` as Post Init Script with Type `Command` from the TrueNAS web interface. If you want to automatically install systemd-nspawn if it's not already installed (recommended to keep working after a TrueNAS SCALE update) then you may use a command such as this instead: `/mnt/mypool/jailmaker/jlmkr.py install && /mnt/mypool/jailmaker/jlmkr.py start myjail`.
 
 ## Additional Commands
 
@@ -128,8 +138,6 @@ To make passthrough of the nvidia GPU work, you need to schedule a Pre Init comm
 
 TODO: write comparison between systemd-nspawn (without jailmaker), LXC, VMs, Docker (on the host).
 
-## Known Issues
-
 ### Incompatible Distros
 
 The rootfs image `jlmkr.py` downloads comes from the [Linux Containers Image server](https://images.linuxcontainers.org). These images are made for LXC. We can use them with systemd-nspawn too, although not all of them work properly. For example, the `alpine` image doesn't work well. If you stick with common systemd based distros (Debian, Ubuntu, Arch Linux...) you should be fine.

jlmkr.py

@@ -4,6 +4,7 @@ import argparse
 import configparser
 import contextlib
 import ctypes
+import glob
 import hashlib
 import os
 import re
@@ -32,9 +33,9 @@ DISCLAIMER = f"""{YELLOW}{BOLD}USE THIS SCRIPT AT YOUR OWN RISK!
 IT COMES WITHOUT WARRANTY AND IS NOT SUPPORTED BY IXSYSTEMS.{NORMAL}"""
 
 DESCRIPTION = "Create persistent Linux 'jails' on TrueNAS SCALE, with full access to all files \
-    via bind mounts, without modifying the host OS thanks to systemd-nspawn!"
+    via bind mounts, thanks to systemd-nspawn!"
 
-VERSION = '0.0.4'
+VERSION = '0.0.5'
 
 JAILS_DIR_PATH = 'jails'
 JAIL_CONFIG_NAME = 'config'
@@ -768,6 +769,33 @@ def list_jails():
     print("\nCurrently running:\n")
     subprocess.run(['machinectl', 'list'])
 
+def install_jailmaker_dependencies():
+    # Check if command exists in path
+    if shutil.which('systemd-nspawn'):
+        print("systemd-nspawn is already installed.")
+        return
+    
+    print("Installing jailmaker dependencies...")
+
+    original_permissions = {}
+
+    print("Temporarily enable apt and dpkg (if not already enabled) to install systemd-nspawn.")
+
+    # Make /bin/apt* and /bin/dpkg* files executable
+    for file in (glob.glob('/bin/apt*') + (glob.glob('/bin/dpkg*'))):
+        original_permissions[file] = os.stat(file).st_mode
+        stat_chmod(file, 0o755)
+
+    subprocess.run(['apt-get', 'update'], check=True)
+    subprocess.run(['apt-get', 'install', '-y', 'systemd-container'], check=True)
+
+    # Restore original permissions
+    print("Restore permissions of apt and dpkg.")
+
+    for file, original_permission in original_permissions.items():
+        stat_chmod(file, original_permission)
+
+    print("Done installing jailmaker dependencies.")
 
 def main():
     if os.stat(__file__).st_uid != 0:
@@ -791,6 +819,8 @@ def main():
 
     subparsers.add_parser(name='list', epilog=DISCLAIMER)
 
+    subparsers.add_parser(name='install', epilog=DISCLAIMER, help="Install jailmaker dependencies")
+
     if os.getuid() != 0:
         parser.print_usage()
         fail("Run this script as root...")
@@ -816,6 +846,9 @@ def main():
     elif args.subcommand == 'list':
         list_jails()
 
+    elif args.subcommand == 'install':
+        install_jailmaker_dependencies()
+
     elif args.subcommand:
         parser.print_usage()