Add the multiinstance doc

ChangeLog

@@ -2,6 +2,7 @@
 
 0.7.1rc2
     * Add an automatic PrusaLink image builder script
+    * Add multi-instance documentation
 
 0.7.1rc1 (2023-08-10)
     * Fixed HTTP response status on HEAD request for non-existing files

MULTIINSTANCE.md

@@ -0,0 +1,77 @@
+# PrusaLink multi instance
+In this mode, an instance of PrusaLink is created for each new printer
+detected on any of the USB ports of the host system, allowing the user
+to connect multiple printers using a single Raspberry Pi.
+
+## Setup
+The multi instance image requires the same setup as the regular one,
+but there are some differences
+
+1) The multi-instance manager does not connect to printers on the GPIO
+pins as the device udev auto-detection in Linux does not work on those
+2) Cameras automatically connect to the first instance only. If you wish
+to use for example a camera for each printer, you'll need to manually
+copy over relevant configuration
+3) In this image, the manager of these PrusaLink instances is run as root.
+However web interface of the instance manager is run under the user account.
+
+### Cameras
+The temporary process of connecting multiple cameras is not user friendly
+and requires manual work. This will change in the future.
+The process is as follows:
+1) Connect all cameras you wish to use and let them connect to the first
+instance
+2) Open the web interface of the first instance and under cameras, save
+every camera manually. This will create a configuration section for each
+camera in `prusa_printer_settings.ini` of the first instance
+3) Using ssh, navigate to `/etc/prusalink/prusalink1.ini` and open it
+4) Turn off the camera auto-detection in the first instance by adding
+this section into the file
+    ```
+    [cameras]
+    auto_detect = False
+    ```
+5) Navigate to `/home/<username>/PrusaLink1` and open
+`prusa_printer_settings.ini`
+6) Move the section corresponding to each camera over to the instance in which
+you wish to use it. The camera sections have hashes as names,
+the order of which is noted in the section `[camera_order]`
+7) Move the camera order entry for each camera as well.
+A camera order section with a single camera in it looks like this
+    ```
+    [camera_order]
+    1 = asdfghjkl
+    ```
+8) After a reboot, the cameras should be connected to the correct instances
+
+## Running the manager
+To run PrusaLink in the multi-instance mode run `prusalink-manager start`
+as root. There are other options allowing you to specify which user to run the
+instances and web under. The default is UID = 1000
+
+Here's the help output of prusalink-manager
+
+```
+Multi-instance suite for PrusaLink
+
+positional arguments:
+  {start,stop,clean,rescan}
+                        Available commands
+    start               Start the instance managing daemon (needs root
+                        privileges)
+    stop                Stop any manager daemon running (needs root
+                        privileges)
+    clean               Danger! cleans all PrusaLink multi-instance
+                        configuration
+    rescan              Notify the daemon a printer has been connected
+
+options:
+  -h, --help            show this help message and exit
+  -i, --info            include log messages up to the INFO level
+  -d, --debug           include log messages up to the INFO level
+  -u USERNAME, --username USERNAME
+                        Which users to use for running and storing everything
+  -p PREPEND_EXECUTABLES_WITH, --prepend-executables-with PREPEND_EXECUTABLES_WITH
+                        Environment variables and path to the executables
+                        directory
+```

README.md

@@ -111,6 +111,10 @@ similar redirect on the loopback interface
 iptables -t nat -I OUTPUT -p tcp -o <loopback device name> -d localhost --dport 80 -j REDIRECT --to-ports 8080
 ```
 
+### Multi-instance
+If you want to connect multiple printers to a single pi, have a look at
+[MULTIINSTANCE.md](MULTIINSTANCE.md)
+
 ## Usage
 By default, the executable starts the daemon process and exits.
 The executable is called `prusalink` and can be used to control the daemon,

prusa/link/multi_instance/__main__.py

@@ -223,7 +223,7 @@ def main():
     """The main function for the PrusaLink instance manager.
     Parses command-line arguments and runs the instance controller"""
     parser = argparse.ArgumentParser(
-        description="Multi instance suite for PrusaLink")
+        description="Multi-instance suite for PrusaLink")
 
     parser.add_argument("-i",
                         "--info",
@@ -255,7 +255,7 @@ def main():
 
     subparsers.add_parser(
         "clean",
-        help="Danger! cleans all PrusaLink multi instance configuration")
+        help="Danger! cleans all PrusaLink multi-instance configuration")
 
     # Create a subparser for the printer_connected command
     subparsers.add_parser(