Sorry I did not provide enough info. I am using Debian bookworm, completely updated as far as I know, and it looks like you might be using Ubuntu. Maybe I needed to use bookworm-backports as you suggested; it looks like a newer version there. I've actually found another way to do what I was trying to do with v4l2loopback and don't need it anymore, but thanks for looking at it.
Here is some output that you asked for:
_ _ _
/_\ _ _ _ __ | |__(_)__ _ _ _
/ _ \| '_| ' \| '_ \ / _` | ' \
/_/ \_\_| |_|_|_|_.__/_\__,_|_||_|
v25.5.1 for Renegade running Armbian Linux 6.12.32-current-rockchip64
Packages: Debian stable (bookworm)
IPv4: (LAN) 10.0.44.17, 192.168.4.254 (WAN) 107.77.207.5
Performance:
Load: 50% Up time: 0 min
Memory usage: 13% of 968M
CPU temp: 36°C Usage of /: 13% of 30G
Commands:
Configuration : armbian-config
Monitoring : htop
Last login: Sat Jul 5 20:21:20 2025 from 10.0.44.1
pburt@gato:~$ cat /etc/debian_version
12.11
pburt@gato:~$ apt-cache policy v4l2loopback-dkms
v4l2loopback-dkms:
Installed: (none)
Candidate: 0.12.7-2
Version table:
0.13.2-1~bpo12+1 100
100 http://deb.debian.org/debian bookworm-backports/main arm64 Packages
100 http://deb.debian.org/debian bookworm-backports/main armhf Packages
0.12.7-2 500
500 http://deb.debian.org/debian bookworm/main arm64 Packages
500 http://deb.debian.org/debian bookworm/main armhf Packages
pburt@gato:~$ sudo apt install v4l2loopback-dkms
[sudo] password for pburt:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
dkms
Suggested packages:
menu
Recommended packages:
fakeroot
The following NEW packages will be installed:
dkms v4l2loopback-dkms
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 86.0 kB of archives.
After this operation, 308 kB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1 http://deb.debian.org/debian bookworm/main arm64 dkms all 3.0.10-8+deb12u1 [48.7 kB]
Get:2 http://deb.debian.org/debian bookworm/main arm64 v4l2loopback-dkms all 0.12.7-2 [37.2 kB]
Fetched 86.0 kB in 1s (119 kB/s)
Selecting previously unselected package dkms.
(Reading database ... 71668 files and directories currently installed.)
Preparing to unpack .../dkms_3.0.10-8+deb12u1_all.deb ...
Unpacking dkms (3.0.10-8+deb12u1) ...
Selecting previously unselected package v4l2loopback-dkms.
Preparing to unpack .../v4l2loopback-dkms_0.12.7-2_all.deb ...
Unpacking v4l2loopback-dkms (0.12.7-2) ...
Setting up dkms (3.0.10-8+deb12u1) ...
Setting up v4l2loopback-dkms (0.12.7-2) ...
Loading new v4l2loopback-0.12.7 DKMS files...
Building for 6.12.32-current-rockchip64
Building initial module for 6.12.32-current-rockchip64
Error! Bad return status for module build on kernel: 6.12.32-current-rockchip64 (aarch64)
Consult /var/lib/dkms/v4l2loopback/0.12.7/build/make.log for more information.
dpkg: error processing package v4l2loopback-dkms (--configure):
installed v4l2loopback-dkms package post-installation script subprocess returned error exit status 10
Errors were encountered while processing:
v4l2loopback-dkms
E: Sub-process /usr/bin/dpkg returned an error code (1)
pburt@gato:~$ cat /var/lib/dkms/v4l2loopback/0.12.7/build/make.log
DKMS make.log for v4l2loopback-0.12.7 for kernel 6.12.32-current-rockchip64 (aarch64)
Sun Jul 6 06:20:57 PM CDT 2025
Building v4l2-loopback driver...
make -C /lib/modules/6.12.32-current-rockchip64/build M=/var/lib/dkms/v4l2loopback/0.12.7/build modules
make[1]: Entering directory '/usr/src/linux-headers-6.12.32-current-rockchip64'
CC [M] /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c: In function ‘vidioc_querycap’:
/var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.c:717:9: error: implicit declaration of function ‘strlcpy’; did you mean ‘strncpy’? [-Werror=implicit-function-declaration]
717 | strlcpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
| ^~~~~~~
| strncpy
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:229: /var/lib/dkms/v4l2loopback/0.12.7/build/v4l2loopback.o] Error 1
make[2]: *** [/usr/src/linux-headers-6.12.32-current-rockchip64/Makefile:1945: /var/lib/dkms/v4l2loopback/0.12.7/build] Error 2
make[1]: *** [Makefile:224: __sub-make] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-6.12.32-current-rockchip64'
make: *** [Makefile:43: v4l2loopback.ko] Error 2
pburt@gato:~$
