RTL_433 in unprivileged LXC container, with automatic device path change

S

spiralsugarcane

New Member
Jun 6, 2023
17
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My solution for automatically updating the device path of a passed through RTL SDR USB device.
The application running in the container is in my case rtl_433 which can not read a symlink for the USB device.
It needs to be recognised by libusb and I could not get it to work in any other way than passing thrugh the full device path, e.g
Code: 
/dev/bus/usb/001/001

Add a device in the Proxmox GUI to the full device path. (Maybe not necessary?)

#Create a UDEV rule at:
Code: 
/etc/udev/rules.d/20.rtlsdr.rules
Code: 
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0666", SYMLINK+="rtl_sdr", RUN="/usr/share/lxc/lxc-<CT_ID>-read-link.sh"

#Create bash script at:
Code: 
/usr/share/lxc/lxc-<CT_ID>-read-link.sh
Code: 
#!/bin/bash
pct set <CT_ID> --dev0 path=$(readlink -f /dev/rtl_sdr)""
exit 0

#Make script executable:
Code: 
chmod +x /usr/share/lxc/lxc-<CT_ID>-read-link.sh

#Add a line to /etc/pve/lxc/<CT_ID>.conf
Code: 
lxc.hook.pre-start: "udevadm control --reload-rules && udevadm trigger"
This line updates the udev rules before container startup.

I could not get it to work by just inserting
Code: 
"bash -c "pct set 503 --dev0 path=$(readlink -f /dev/rtl_sdr)""
or even the pct command into a bash script. Only the method of letting the udev rule run the script that updates the device path for the container worked.
To get the container to recognise the device at host bootup, I had to set the line that updates udev rules in the lxc config file.

Any comments or improvements?
I can remove and reattach the device, even let it be inserted at host bootup, and the container starts fine.
But if I remove and reinsert the device the container must be restarted.
 
spiralsugarcane said:
My solution for automatically updating the device path of a passed through RTL SDR USB device.
The application running in the container is in my case rtl_433 which can not read a symlink for the USB device.
It needs to be recognised by libusb and I could not get it to work in any other way than passing thrugh the full device path, e.g
Code: 
/dev/bus/usb/001/001

Add a device in the Proxmox GUI to the full device path. (Maybe not necessary?)

#Create a UDEV rule at:
Code: 
/etc/udev/rules.d/20.rtlsdr.rules
Code: 
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0666", SYMLINK+="rtl_sdr", RUN="/usr/share/lxc/lxc-<CT_ID>-read-link.sh"

#Create bash script at:
Code: 
/usr/share/lxc/lxc-<CT_ID>-read-link.sh
Code: 
#!/bin/bash
pct set <CT_ID> --dev0 path=$(readlink -f /dev/rtl_sdr)""
exit 0

#Make script executable:
Code: 
chmod +x /usr/share/lxc/lxc-<CT_ID>-read-link.sh

#Add a line to /etc/pve/lxc/<CT_ID>.conf
Code: 
lxc.hook.pre-start: "udevadm control --reload-rules && udevadm trigger"
This line updates the udev rules before container startup.

I could not get it to work by just inserting
Code: 
"bash -c "pct set 503 --dev0 path=$(readlink -f /dev/rtl_sdr)""
or even the pct command into a bash script. Only the method of letting the udev rule run the script that updates the device path for the container worked.
To get the container to recognise the device at host bootup, I had to set the line that updates udev rules in the lxc config file.

Any comments or improvements?
I can remove and reattach the device, even let it be inserted at host bootup, and the container starts fine.
But if I remove and reinsert the device the container must be restarted.
Click to expand...
Hi, the best solution that I'd seen in my opinion. Simple, functional and elegant. However, I follow this steps but the script doesn't run at CT startup. If I run
Code: 
udevadm control --reload-rules && udevadm trigger
in PVE host, it executes the script without problems.
 
albertososa said:
Hi, the best solution that I'd seen in my opinion. Simple, functional and elegant. However, I follow this steps but the script doesn't run at CT startup. If I run
Code: 
udevadm control --reload-rules && udevadm trigger
in PVE host, it executes the script without problems.
Click to expand...
Nice :) Can you try making a bash script somwhere like /usr/share/lxc/lxc-<CT_ID>-udev.sh

Code: 
#!/bin/bash
udevadm control --reload-rules && udevadm trigger

Make executable:
chmod +x /usr/share/lxc/lxc-<CT_ID>-udev.sh

And then reference the script in the lxc hook like:

Code: 
lxc.hook.pre-start: "chmod +x /usr/share/lxc/lxc-<CT_ID>-udev.sh"
 
spiralsugarcane said:
Nice :) Can you try making a bash script somwhere like /usr/share/lxc/lxc-<CT_ID>-udev.sh

Code: 
#!/bin/bash
udevadm control --reload-rules && udevadm trigger

Make executable:
chmod +x /usr/share/lxc/lxc-<CT_ID>-udev.sh

And then reference the script in the lxc hook like:

Code: 
lxc.hook.pre-start: "chmod +x /usr/share/lxc/lxc-<CT_ID>-udev.sh"
Click to expand...
The main problem is that no script is called before CT start. No matter what the script is. Of course, it's executable.
 
albertososa said:
The main problem is that no script is called before CT start. No matter what the script is. Of course, it's executable.
Click to expand...

Maybe it can be wise to use the pct create command instead of creating the container via GUI. Then you can specify the --hookscript flag according to the pct command documentation:

--hookscript <string>
Script that will be executed during various steps in the containers lifetime.
Click to expand...
 
spiralsugarcane said:
My solution for automatically updating the device path of a passed through RTL SDR USB device.
The application running in the container is in my case rtl_433 which can not read a symlink for the USB device.
It needs to be recognised by libusb and I could not get it to work in any other way than passing thrugh the full device path, e.g
Code: 
/dev/bus/usb/001/001

Add a device in the Proxmox GUI to the full device path. (Maybe not necessary?)

#Create a UDEV rule at:
Code: 
/etc/udev/rules.d/20.rtlsdr.rules
Code: 
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0666", SYMLINK+="rtl_sdr", RUN="/usr/share/lxc/lxc-<CT_ID>-read-link.sh"

#Create bash script at:
Code: 
/usr/share/lxc/lxc-<CT_ID>-read-link.sh
Code: 
#!/bin/bash
pct set <CT_ID> --dev0 path=$(readlink -f /dev/rtl_sdr)""
exit 0

#Make script executable:
Code: 
chmod +x /usr/share/lxc/lxc-<CT_ID>-read-link.sh

#Add a line to /etc/pve/lxc/<CT_ID>.conf
Code: 
lxc.hook.pre-start: "udevadm control --reload-rules && udevadm trigger"
This line updates the udev rules before container startup.

I could not get it to work by just inserting
Code: 
"bash -c "pct set 503 --dev0 path=$(readlink -f /dev/rtl_sdr)""
or even the pct command into a bash script. Only the method of letting the udev rule run the script that updates the device path for the container worked.
To get the container to recognise the device at host bootup, I had to set the line that updates udev rules in the lxc config file.

Any comments or improvements?
I can remove and reattach the device, even let it be inserted at host bootup, and the container starts fine.
But if I remove and reinsert the device the container must be restarted.
Click to expand...
Thanks for this! It's exactly what I was looking for. I used this technique to adjust the usb paths for 2 devices being passed through to a container after host reboot.

I can't seem to get the pre-start hook to ever work with my setup. Not sure if it's because my container is unpriviliged maybe.

What I ended up doing was just running the udevadm reload/trigger commands within a host reboot script I made in a cron job. I did that and then a short pause before starting the container. Works perfectly! Thanks again.
 
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