The DKMS mechanism is a convenient way to have extra Linux kernel modules managed outside of the kernel tree source to survive kernel updates.
Once the v4l2loopback_dc module, which is necessary for Droidcam to work, has been built and installed, you may face at some point that after a system update, implying a kernel update, Droidcam may not work anymore... when running droidcam, it may fail starting with the following message:
Device not found (/dev/video[0-9]).
Did you install it?
This is just because the newly installed kernel does not come with the v4l2loopback_dc module, thus you would then have to re-install it manually again. You may have forgotten what you did the first time, have to dig again into documentation, how you did it on the first place...
This is where DKMS comes into the picture.
By properly declaring the v4l2loopback_dc module as a DKMS module, future installs of kernel upgrades will automatically take v4l2loopback_dc module re-installation into account after the kernel has been updated.
If your system supports DKMS, it should probably be your prefered install mechanism. Both for the fact it survives kernel updates, but also for the fact it keeps your kernel module tree clean, as extra DKMS modules are kept in separated directories.
First clone the droidcam Github repo anywhere you want (in /opt for example):
$ git clone https://github.com/dev47apps/droidcam.git
Build it following the standard procedure described here.
ℹ️ The pre-requisite for what's coming next is that the previous build succeeded.
From within the repository, go to the linux directory, and then issue a:
$ sudo ./install-dkms [width] [height]
If you want specific webcam resolution, you can directly pass the width and height to the script (as for the standard install script). Default is 640 480.
ℹ️ After this, the module is built, loaded (you may check this using lsmod|grep v4l2loopback_dc), and its config for the webcam resolution is created in the file /etc/modprobe.d/droidcam.conf (you may want to edit this file afterwards, or you can re-run the install script multiple times with different parameters which is harmless). Supported webcam resolutions are listed here.
From within the repository, go to the linux directory, and then issue a:
$ sudo ./uninstall-dkms
Or alternatively, in case you removed the original repository after install, you can issue:
$ sudo /opt/droidcam-uninstall