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I'm using OBS Studio and would like to have a virtual video output saved permanently so that it can be run when the application is launched.

This command creates the virtual output:

sudo modprobe v4l2loopback video_nr=10 card_label="OBS Video Source" exclusive_caps=1

But I must run the command in console on each boot. How can I make this permanent? The plugin that utilizes the output in OBS Studio is configured to auto start but /dev/video10 is not available after a reboot of the system.

$ modinfo v4l2loopback | grep -i parm
parm:           debug:debugging level (higher values == more verbose) (int)
parm:           max_buffers:how many buffers should be allocated (int)
parm:           max_openers:how many users can open loopback device (int)
parm:           devices:how many devices should be created (int)
parm:           video_nr:video device numbers (-1=auto, 0=/dev/video0, etc.) (array of int)
parm:           card_label:card labels for every device (array of charp)
parm:           exclusive_caps:whether to announce OUTPUT/CAPTURE capabilities exclusively or not (array of bool)
parm:           max_width:maximum frame width (int)
parm:           max_height:maximum frame height (int)
Eliah Kagan
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Mark Lee
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  • One on the proper methods was to add the module name to the /etc/modules file . But nowadays the udev subsystem should insert the required drivers automatically . But if you are sure that it doesn't , add the name of the module to the modules file and reboot to check out the result. – Parsa Mousavi May 30 '20 at 15:56
  • There's an /etc/modprobe.d and /etc/modules-load.d but no /etc/modules directory on my system. – Mark Lee May 30 '20 at 16:12
  • @Parsa Mousavi, I had erroneously looked for an /etc/modules folder rather than a file. – Mark Lee May 30 '20 at 22:12

2 Answers2

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Normally kernel modules can be added to /etc/modules for loading at boot time.

Add this to /etc/modules...

v4l2loopback video_nr=10 card_label="OBS Video Source" exclusive_caps=1

However, I don't know if you can pass parameters there. So here's another way to do it.

Add this to /etc/modules...

v4l2loopback

Create /etc/modprobe.d/v4l2loopback.conf

options v4l2loopback video_nr=10 card_label="OBS Video Source" exclusive_caps=1

Then...

sudo update-initramfs -c -k $(uname -r)

reboot

Confirm module loading with...

lsmod | grep -i v4l2loopback
heynnema
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  • I created /etc/modprobe.d/v4l2loopback.conf with the option and rebooted and the loopback seems to have loaded. I'll shut down and restart presently because I noticed that sometimes a reboot comes up with the settings that were present. The result of grep same as before reboot: v4l2loopback 40960 0 videodev 225280 4 videobuf2_v4l2,v4l2loopback,uvcvideo,videobuf2_common – Mark Lee May 30 '20 at 16:48
  • @MarkLee You added the line to /etc/modules, yes? I added an update-initramfs command to my procedure. – heynnema May 30 '20 at 16:51
  • @MarkLee Edit your question and show me `modinfo v4l2loopback | grep -i parm`. – heynnema May 30 '20 at 17:00
  • There's no /etc/modules on my system. – Mark Lee May 30 '20 at 17:04
  • @MarkLee Create one. `sudo pico /etc/modules`. Just add `v4l2loopback` to it. Then do the update-initramfs command. Then reboot. – heynnema May 30 '20 at 17:06
  • op edited as requested. – Mark Lee May 30 '20 at 20:37
  • @MarkLee After creating both files and doing the update-initramfs, and rebooting, is it all working now? – heynnema May 30 '20 at 20:41
  • It didn't work and as I checked /etc/modprobe.d/v4l2loopback.conf just now what was listed in the directory instead was v4l2loopback.conf.save. I just wrote the file again and am about to reboot once more. – Mark Lee May 30 '20 at 20:44
  • Keep me posted. – heynnema May 30 '20 at 20:52
  • I think you've got me over the hump. After a few glitches--1. OBS refused to start (commented out the line in the conf and it started), 2. started with no connection to the camera (stopped the plug-in and uncommented the conf)--I have camera input and video10 output on starting. Hopefully not a one off "magic". Thanks. – Mark Lee May 30 '20 at 21:40
  • @MarkLee Sounds great... I think... so, to sum up... you were able to complete the second procedure in my answer... and it seems to be working now? – heynnema May 30 '20 at 21:48
  • Can't get this to work on 20.04. `lsmod | grep -i v4l2loopback` doesn't print anything. `❯ cat /etc/modprobe.d/v4l2loopback.conf options v4l2loopback video_nr=10 card_label="OBS Video Source" exclusive_caps=1` – Vala Sep 01 '20 at 15:04
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    @Thor84no Did you add v4l2loopback to /etc/modules, create the .conf file, update-initramfs, and reboot? – heynnema Sep 01 '20 at 15:22
  • Oh, I didn't realise the `v4loopback` to `/etc/modules` was required in addition to the `/etc/modprobe.d/v4l2loopback.conf`, sorry. I guess I misread your post. It seems to work now. Thanks! – Vala Sep 03 '20 at 08:41
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Easy way to do it un Ubuntu 20.04 and others:

$ sudo echo "v4l2loopback" > /etc/modules-load.d/v4l2loopback.conf 
$ sudo echo "options v4l2loopback video_nr=10 card_label=\"OBS Video Source\" exclusive_caps=1" > /etc/modprobe.d/v4l2loopback.conf

You can restart to check it works!

NOTICE

Be aware of a bug on v4l2loopback-dkms 0.12.3-1ubuntu0.1

More info on this stackoverflow post.

EDIT - Using tee

As pointed by renyhp, it's better to use the tee command:

$ sudo echo "v4l2loopback" | tee /etc/modules-load.d/v4l2loopback.conf 
$ sudo echo "options v4l2loopback video_nr=10 card_label=\"OBS Video Source\" exclusive_caps=1" | tee /etc/modprobe.d/v4l2loopback.conf

EDIT - Update modules

As commented, it seems that in some systems after rebooting some problems can be experienced. To avoid that, it's always a good idea to update the modules:

sudo update-initramfs -c -k $(uname -r)
PabloRQ
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    This is the simple answer, but it will give Permission denied, since sudo applies to echo and not to redirection. You may actually want to pipe echo into sudo tee – renyhp Dec 03 '20 at 08:26
  • Actually: yes, if it used sudo tee this would be the simple way to add the needed configurations. And thank you for the warning about the bug. However, DO NOT FORGET TO DO `sudo update-initramfs -c -k $(uname -r)` as the other answer reported. I didn't, and I regretted it (keyboard not working; had to run a live Ubuntu to remove the conf files under etc) – renyhp Dec 03 '20 at 09:07
  • for me, i have trouble to downgrade v4l2loopback-dkms (installed v4l2loopback-dkms package post-installation script subprocess returned error exit status 1) – ses just now actually I already have 0.12.3-1ubuntu0.4 - and problem is there too. not sure where to downgrade then.. even if I did not have error 1 – ses Aug 29 '21 at 05:06
  • @renyhp: thank you for your comments. The solution was updated. – PabloRQ Aug 30 '21 at 11:13
  • @ses I've already commented this in the other solution. – PabloRQ Aug 30 '21 at 11:15