PrusaLink in an LXC Container on Proxmox

Prusalink “is the client-side running locally on your printer, accessible from local network.” Except I am installing it in an LXC container on a ProxMox host, which is connected to the printer via a USB cable.

Sources:

This is similar to the way I used to run octoprint.

Create an LXC Container

host: prusalink (pick your own name as desired)
template: Debian 12 standard 12.7-1
disk: 8GB
CPU cores: 2
Memory: 512MB
Network: DHCP, DHCP configured for static lease
Firewall: off

Start the LXC. At this point I usually:

configure the static DHCP lease on my DHCP server for this LXC if the LXC will expose a web service, the way prusalink will.
disable ipv6 by adding net.ipv6.conf.all.disable_ipv6=1 to /etc/sysctl.conf

Restart the LXC and confirm (using ip a) the LXC is assigned the IP address you expected.

Upgrade OS

In the lxc console, after logging in as a root:

apt update
apt upgrade

Install the Prerequisites

apt install -y git libcap-dev libturbojpeg0 libatlas-base-dev \
    libffi-dev gcc sudo ffmpeg curl

Note: ffmpeg is for webcam - skip it if you do not use one.

Install python prerequisites - not sure all these are needed though:

apt install -y python3-dev python3-full python3-pip python3-numpy

Create User pi

Still in the console as root:

adduser pi
usermod -a -G adm,sudo,tty,dialout,video pi

Group dialout membership is required in order to talk to the printer via USB port. Group video membership is required in order to get images from the webcam.

The next steps are executed in the context of user pi.

Install PrusaLink Software

python3 -m venv venv-prusalink

and activate it:

source venv-prusalink/bin/activate

Install Prusa-Link software into the virtual environment:

pip install --no-cache-dir \
    git+https://github.com/prusa3d/gcode-metadata.git \
    git+https://github.com/prusa3d/Prusa-Connect-SDK-Printer.git \
    git+https://github.com/prusa3d/Prusa-Link.git

Use pip freeze to list all the venv packages installed and their versions.

Create PrusaLink Directories

Prepare the PrusaLink directories:

sudo mkdir /etc/prusalink
sudo chown -R pi:pi /etc/prusalink

Create the default PrusaLink configuration file:

wget https://raw.githubusercontent.com/prusa3d/Prusa-Link/refs/heads/master/prusa/link/data/prusalink.ini
mv prusalink.ini /etc/prusalink/

Pass Through Printer’s USB port and tty to the LXC

Identify the printer’s USB port and tty to pass through:

root@suprox:~# lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 0c45:636b Microdia USB  Live camera
Bus 001 Device 008: ID 2c99:0002 Prusa Original Prusa i3 MK3
Bus 001 Device 005: ID 0557:2419 ATEN International Co., Ltd Virtual mouse/keyboard device
Bus 001 Device 004: ID 0557:7000 ATEN International Co., Ltd Hub
Bus 001 Device 006: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

root@suprox:~# ls -la /dev/bus/usb/001/008
crw-rw-r-- 1 root root 189, 7 Nov 10 18:05 /dev/bus/usb/001/008

root@suprox:~# ls -la /dev/ttyACM0
crw-rw-rw- 1 root dialout 166, 0 Nov 10 18:05 /dev/ttyACM0

Now we know that:

we need to pass through Bus 001 Device 008
the vendor is 2c99 and the product is 0002
note cgroup is 189

My prusalink lxc ID is 109, so I did this on the proxmox:

mkdir -p /lxc/109/devices
cd /lxc/109/devices/
mknod -m 660 ttyACM0 c 189 0
chown 100000:100020 ttyACM0

Edit /etc/pve/nodes/<host>/lxc/<id>.conf, and add the following lines:

lxc.cgroup2.devices.allow: c 189:* rwm
lxc.mount.entry: /dev/bus/usb/001/008 dev/bus/usb/001/008 none bind,optional,create=file
lxc.mount.entry: /lxc/<id>/devices/ttyACM0 dev/ttyACM0 none bind,optional,create=file

Edit /etc/udev/rules.d/50-usb.rules:

SUBSYSTEM=="tty", ATTRS{idVendor}=="2c99", ATTRS{idProduct}=="0002", MODE="0666", SYMLINK+="prusa"

And then:

udevadm control --reload-rules && service udev restart && udevadm trigger

Reboot the LXC then login as pi and verify the port is indeed passed through:

pi@prusalink:~$ ls -la /dev/tty*
crw-rw-rw- 1 nobody nogroup   5, 0 Nov 17 00:17 /dev/tty
crw------- 1 pi     tty     136, 1 Nov 17 00:17 /dev/tty1
crw--w---- 1 root   tty     136, 2 Nov 17 00:17 /dev/tty2
crw-rw---- 1 root   dialout 166, 0 Nov 17 00:12 /dev/ttyACM0

Configure PrusaLink

As user pi: edit /etc/prusalink/prusalink.ini to update the port configured in the previous section:

[printer]
port = /dev/ttyACM0

Start PrusaLink

First, let’s start PrusaLink manually. As user pi activate virtual environment:

source venv-prusalink/bin/activate

By now you have everything to start prusalink:

(venv-prusalink) pi@prusalink:~$ which prusalink
/home/pi/venv-prusalink/bin/prusalink

(venv-prusalink) pi@prusalink:~$ prusalink -h
usage: prusalink [-h] [-f] [-c <file>] [-p <FILE>] [-a <ADDRESS>] [-t <PORT>] [-I] [-s <PORT>] [-n PRINTER_NUMBER] [-i] [-d] [-l MODULE_LOG_LEVEL] [--profile]
                 [--version]
                 [command]

PrusaLink daemon.

positional arguments:
  command               daemon action (start|stop|restart|status) (default: start)

options:
  -h, --help            show this help message and exit
  -f, --foreground      run as script on foreground
  -c <file>, --config <file>
                        path to config file (default: /etc/prusalink/prusalink.ini)
  -p <FILE>, --pidfile <FILE>
                        path to pid file
  -a <ADDRESS>, --address <ADDRESS>
                        IP listening address (host or IP)
  -t <PORT>, --tcp-port <PORT>
                        TCP/IP listening port
  -I, --link-info       /link-info debug page
  -s <PORT>, --serial-port <PORT>
                        Serial (printer's) port or 'auto'
  -n PRINTER_NUMBER, --printer-number PRINTER_NUMBER
                        Multi-instance printer number to show in wizard
  -i, --info            more verbose logging level INFO is set
  -d, --debug           DEBUG logging level is set
  -l MODULE_LOG_LEVEL, --module-log-level MODULE_LOG_LEVEL
                        sets the log level of any submodule(s). use <module_path>=<log_level>
  --profile             Use cProfile for profiling application.
  --version             Print out version info and exit

(venv-prusalink) pi@prusalink:~$ prusalink --version
PrusaLink version: 0.8.1
PrusaConnect-SDK version: 0.8.1

Start prusalink in the foreground to do debugging:

prusalink -f

Point your browser to http://<ip>:8080 to complete configuration.

Automatic Start-up

To make sure prusalink auto-starts, let’s create a systemd service.

Create unit file /etc/systemd/system/prusalink.service, reference:

[Unit]
Description=PrusaLink Service
After=network.target
Wants=network-online.target

[Service]
Type=simple
User=pi
Group=pi
WorkingDirectory=/home/pi
Environment="LC_ALL=C.UTF-8"
Environment="LANG=C.UTF-8"
ExecStart=/home/pi/venv-prusalink/bin/prusalink start
ExecStop=/home/pi/venv-prusalink/bin/prusalink stop
Restart=on-abort

[Install]
WantedBy=multi-user.target

Enable the prusalink service:

sudo systemctl enable prusalink.service

More on systemctl and systemctl services.

To (re)start the service:

sudo systemctl restart prusalink.service

To check the service status:

systemctl status prusalink.service --no-pager

To check the prusalink service logs:

journalctl --no-pager --unit=prusalink

Passthrough USB Webcam Device(s) to the LXC Container

Prepare the Proxmox Node Device(s)

Identify the USB device associated with the webcam on the proxmox host:

root@suprox:~# lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 0c45:636b Microdia USB  Live camera
Bus 001 Device 008: ID 2c99:0002 Prusa Original Prusa i3 MK3
Bus 001 Device 005: ID 0557:2419 ATEN International Co., Ltd Virtual mouse/keyboard device
Bus 001 Device 004: ID 0557:7000 ATEN International Co., Ltd Hub
Bus 001 Device 006: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Looks like the webcam is device 003 on the bus 001:

root@suprox:~# ls -la /dev/bus/usb/001/003
crw-rw-r-- 1 root root 189, 2 Nov 16 17:10 /dev/bus/usb/001/003

Note cgroup is 189, we will need this information later.

Set the owner of the webcam device on the pve node to the unprivileged uid of your container (100000 by default):

chown 100000:100000 /dev/bus/usb/001/003

Check the V4L devices:

root@suprox:~#  ls -la /dev/video*
crw-rw---- 1 root video 81, 0 Nov 16 17:10 /dev/video0
crw-rw---- 1 root video 81, 1 Nov 16 17:10 /dev/video1

Set the owner of V4L devices on the pve node to the unprivileged uid of your container (100000 by default) and group video:

root@suprox:~# grep video /etc/group
video:x:44:
root@suprox:~# chown 100000:100044 /dev/video0
root@suprox:~# chown 100000:100044 /dev/video1
root@suprox:~# ls -la /dev/video*
crw-rw---- 1 100000 100044 81, 0 Nov 16 17:10 /dev/video0
crw-rw---- 1 100000 100044 81, 1 Nov 16 17:10 /dev/video1

To summarize:

we need to pass through Bus 001 Device 003;
the vendor is 0c45 and the product is 636b;
the cgroup is 189;
prusalink container ID is 109.

Edit /etc/pve/lxc/109.conf, and add the following lines:

lxc.cgroup2.devices.allow: c 189:* rwm
lxc.mount.entry: /dev/bus/usb/001/003 dev/bus/usb/001/003 none bind,optional,create=file
lxc.mount.entry: /dev/video0 dev/video0 none bind,optional,create=file
lxc.mount.entry: /dev/video1 dev/video1 none bind,optional,create=file

Check the webcam devices in the PrusaLink LXC Container

Restart yur LXC prusalink container in order for the changes made in the previous section to take the effect.

Verify that the webcam devices are now exposed in the container. In the LXC console as a root:

root@prusalink:~# ls -la /dev/bus/usb/001/003
crw-rw-r-- 1 root root 189, 2 Nov 17 01:10 /dev/bus/usb/001/003
root@prusalink:~# ls -la /dev/video*
crw-rw---- 1 root video 81, 0 Nov 17 01:10 /dev/video0
crw-rw---- 1 root video 81, 1 Nov 17 01:10 /dev/video1

To identify the V4L device to use I installed into the container ffmpeg with apt install ffmpeg and then identified the formats supported by the webcam:

root@prusalink:~# ffmpeg -f v4l2 -list_formats all -i /dev/video0
...
[video4linux2,v4l2 @ 0x63f41de2fe00] Compressed:       mjpeg :          Motion-JPEG : 640x480 1600x896 1280x720 1024x768 1024x576 960x544 864x480 848x480 800x448 640x360 352x288 320x240 1920x1080
[video4linux2,v4l2 @ 0x63f41de2fe00] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x480 1600x896 1280x720 1024x768 1024x576 960x544 864x480 848x480 800x448 640x360 352x288 320x240 1920x1080

For /dev/video1 this command fails:

root@prusalink:~# ffmpeg -f v4l2 -list_formats all -i /dev/video1
...
[video4linux2,v4l2 @ 0x5892f8f6ce00] ioctl(VIDIOC_G_INPUT): Inappropriate ioctl for device

Connect LXC Container webcam to PrusaConnect

This broadly follows Use Raspberry Pi and Pi Cam for Prusa Connect.

Get the token:

Go to the Cameras section at https://connect.prusa3d.com
Add a new camera “Add new other camera”.
Copy the generated Token

Create ~pi/prusaconnect_upload_cam.sh

#!/bin/bash
#
# Script is from
# https://gist.github.com/moritzmhmk/48e5ed9c4baa5557422f16983900ca95
# https://gist.github.com/nunofgs/84861ee453254823be6b069ebbce9ad2

# Set default values for environment variables
: "${HTTP_URL:=https://connect.prusa3d.com/c/snapshot}"
: "${DELAY_SECONDS:=10}"
: "${LONG_DELAY_SECONDS:=60}"
# FINGERPRINT is a random string with at least 16 characters
: "${FINGERPRINT:=123456789012345678}"
# CAMERA_TOKEN generated by the Connect server
: "${CAMERA_TOKEN:=put the token here}"
# V4L device to use
: "${V4L_DEVICE:=/dev/video0}"


while true; do
  # Grab a frame from the webcam using FFmpeg, -video_size 1280x720
  ffmpeg -loglevel warning -y -f video4linux2 -input_format mjpeg \
    -i "$V4L_DEVICE" -video_size 1280x720 -vframes 1 -f mjpeg /tmp/output.jpg

  # If no error, upload it.
  if [ $? -eq 0 ]; then
    # POST the image to the HTTP URL using curl
    curl -X PUT "$HTTP_URL" \
      -H "accept: */*" \
      -H "content-type: image/jpg" \
      -H "fingerprint: $FINGERPRINT" \
      -H "token: $CAMERA_TOKEN" \
      --data-binary "@/tmp/output.jpg" \
      --no-progress-meter \
      --compressed

    # Reset delay to the normal value
    DELAY=$DELAY_SECONDS
  else
    echo "FFmpeg returned an error. Retrying after ${LONG_DELAY_SECONDS}s..."
    # Set delay to the longer value
    DELAY=$LONG_DELAY_SECONDS
  fi
  sleep "$DELAY"
done

Then chmod +x prusaconnect_upload_cam.sh.

Start the script with ./prusaconnect_upload_cam.sh

If it works you should see the images appearing in Prusa Connect every 10 seconds.

Create unit file /etc/systemd/system/prusaconnect_upload_cam.service:

[Unit]
Description=WebCam to Prusa Connect
After=network.target
Wants=network-online.target

[Service]
User=pi
Group=pi
WorkingDirectory=/home/pi
ExecStart=/home/pi/prusaconnect_upload_cam.sh

[Install]
WantedBy=multi-user.target

Then:

sudo systemctl enable prusaconnect_upload_cam.service

Start it:

sudo systemctl start prusaconnect_upload_cam.service

By now, every time your LXC starts:

prusalink.service is launched and connects your printer to prusaconnect.
prusaconnect_upload_cam.service starts uploading webcam images every 10 seconds

Adding a Second Webcam

After plugging the webcam into the server, and in the host shell as a root…

Host USB Devices

Identify the USB device:

root@suprox:~# lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 0c45:636b Microdia USB  Live camera
Bus 001 Device 008: ID 2c99:0002 Prusa Original Prusa i3 MK3
Bus 001 Device 010: ID 1bcf:28c4 Sunplus Innovation Technology Inc. FHD Camera Microphone
Bus 001 Device 005: ID 0557:2419 ATEN International Co., Ltd Virtual mouse/keyboard device
Bus 001 Device 004: ID 0557:7000 ATEN International Co., Ltd Hub
Bus 001 Device 006: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I see a new FHD Camera Microphone… but not the camera? Check the USB device:

root@suprox:~# ls -la /dev/bus/usb/001/010
crw-rw-r-- 1 root root 189, 9 Nov 23 10:37 /dev/bus/usb/001/010

Change the device ownership:

chown 100000:100000 /dev/bus/usb/001/010

Host V4L Devices

Check the V4L devices:

root@suprox:~# ls -la /dev/video*
crw-rw---- 1 100000 100044 81, 0 Nov 16 17:10 /dev/video0
crw-rw---- 1 100000 100044 81, 1 Nov 16 17:10 /dev/video1
crw-rw---- 1 root   video  81, 2 Nov 23 10:37 /dev/video2
crw-rw---- 1 root   video  81, 3 Nov 23 10:37 /dev/video3

I see two new devices: video2 and video3, change their ownership and permissions:

chown 100000:100044 /dev/video2
chown 100000:100044 /dev/video3

Passing the Host Devices through to the LXC Container

To summarize:

we need to pass through Bus 001 Device 010
the vendor is 1bcf and the product is 28c4
the cgroup is 189
prusalink container ID is 109

Edit /etc/pve/lxc/109.conf:

root@suprox:~# cat /etc/pve/lxc/109.conf
## PrusaLink LXC
#
#http%3A//192.168.11.78%3A8080
arch: amd64
cores: 2
features: nesting=1
hostname: prusalink
memory: 512
net0: name=eth0,bridge=vmbr0,hwaddr=BC:24:11:4E:61:25,ip=dhcp,ip6=auto,type=veth
onboot: 1
ostype: debian
rootfs: local-lvm:vm-109-disk-0,size=16G
startup: order=200
swap: 100
unprivileged: 1
lxc.cgroup2.devices.allow: c 189:* rwm
lxc.mount.entry: /dev/bus/usb/001/003 dev/bus/usb/001/003 none bind,optional,create=file
lxc.mount.entry: /dev/bus/usb/001/008 dev/bus/usb/001/008 none bind,optional,create=file
lxc.mount.entry: /dev/bus/usb/001/010 dev/bus/usb/001/010 none bind,optional,create=file
lxc.mount.entry: /lxc/109/devices/ttyACM0 dev/ttyACM0 none bind,optional,create=file
lxc.mount.entry: /dev/video0 dev/video0 none bind,optional,create=file
lxc.mount.entry: /dev/video1 dev/video1 none bind,optional,create=file
lxc.mount.entry: /dev/video2 dev/video2 none bind,optional,create=file
lxc.mount.entry: /dev/video3 dev/video3 none bind,optional,create=file

LXC Container - Devices Verification

After the LXC container restart, in the container console:

pi@prusalink:~$ ls -la /dev/bus/usb/001/003
crw-rw-r-- 1 root root 189, 2 Nov 17 01:10 /dev/bus/usb/001/003

pi@prusalink:~$ ls -la /dev/bus/usb/001/010
crw-rw-r-- 1 root root 189, 9 Nov 23 18:37 /dev/bus/usb/001/010

pi@prusalink:~$ ls -la /dev/video*
crw-rw---- 1 root video 81, 0 Nov 17 01:10 /dev/video0
crw-rw---- 1 root video 81, 1 Nov 17 01:10 /dev/video1
crw-rw---- 1 root video 81, 2 Nov 23 18:37 /dev/video2
crw-rw---- 1 root video 81, 3 Nov 23 18:37 /dev/video3

Looks like the new USB and V4L devices ARE available to LXC.

Verify the new V4L device capabilities:

pi@prusalink:~$ ffmpeg -f v4l2 -list_formats all -i /dev/video2
...
[video4linux2,v4l2 @ 0x56871cf0fe00] Compressed:       mjpeg :          Motion-JPEG : 640x480 1600x896 1280x720 1024x576 800x600 800x480 640x360 424x240 352x288 1920x1080
[video4linux2,v4l2 @ 0x56871cf0fe00] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x480 1600x896 1280x720 1024x576 800x600 800x480 640x360 424x240 352x288 1920x1080

LXC Container - Update the Upload Script to work with the second camera

Create ~pi/prusaconnect_upload_cams.sh

#!/bin/bash
#
# Script is inspired by
# https://gist.github.com/moritzmhmk/48e5ed9c4baa5557422f16983900ca95
# https://gist.github.com/nunofgs/84861ee453254823be6b069ebbce9ad2
#
# Set default values for environment variables
: "${HTTP_URL:=https://connect.prusa3d.com/c/snapshot}"
: "${DELAY_SECONDS:=10}"
: "${LONG_DELAY_SECONDS:=60}"
# FINGERPRINT is a random string with at least 16 characters
: "${FINGERPRINT1:=123456789012345678}"
: "${FINGERPRINT2:=123456789012345678}"
# CAMERA_TOKEN generated by the Connect server
: "${CAMERA_TOKEN1:=put the token here}"
: "${CAMERA_TOKEN2:=put the token here}"

# Grab a frame from the webcam using FFmpeg, -video_size 1280x720
function grab_a_frame {
    local device=$1
    local out_path=$2
    ffmpeg -loglevel warning -y -f video4linux2 -input_format mjpeg \
        -i "$device" -video_size 1280x720 -vframes 1 -f mjpeg "$out_path"
}


# POST the image to the HTTP URL using curl
function upload_a_frame {
    local fingerprint=$1
    local token=$2
    local frame_path=$3
    # POST the image to the HTTP URL using curl
    curl -X PUT "$HTTP_URL" \
      -H "accept: */*" \
      -H "content-type: image/jpg" \
      -H "fingerprint: $fingerprint" \
      -H "token: $token" \
      --data-binary "@$frame_path" --no-progress-meter --compressed
}

while true; do
    # Reset delay to the normal value
    DELAY=$DELAY_SECONDS
    grab_a_frame /dev/video0 /tmp/video0.jpg
    if [ $? -eq 0 ]; then
        upload_a_frame "$FINGERPRINT1" "$CAMERA_TOKEN1" /tmp/video0.jpg
    else
        echo "Error reading /dev/video0. Retrying in ${LONG_DELAY_SECONDS}s..."
        DELAY=$LONG_DELAY_SECONDS
    fi
    grab_a_frame /dev/video2 /tmp/video2.jpg
    if [ $? -eq 0 ]; then
        upload_a_frame "$FINGERPRINT1" "$CAMERA_TOKEN2" /tmp/video2.jpg
    else
        echo "Error reading /dev/video2. Retrying in ${LONG_DELAY_SECONDS}s..."
        DELAY=$LONG_DELAY_SECONDS
    fi
    sleep "$DELAY"
done

update the service file and restart it!

It works!

Known Problems

Framerate of 0.1 fps is…low. Seems to be a PrusaConnect limitation.
Constant (every 10secs) writing of the video frame to the disk is wearing SSD down. If only I had a writable tmpfs file system inside the container…

Notes to Self

Alex Sokolsky's Notes on Computers and Programming