Linux kernel: Difference between revisions

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 $ dmesg | grep hello
 [   82.027229] hello world!
+</syntaxHighlight>
+== Load modules in the kernel ==
+As far as I understand, if you developped a kernel module, you should end up with having some `.ko` files inside a subfolder inside `$out/lib/modules/${kernel.modDirVersion}`. Now, if you want to make your module loadable inside the kernel by `modprobe`, you should do:
+<syntaxHighlight lang=nix>
+boot.extraModulePackages = [ yourmodulename ];
+</syntaxHighlight>
+Then, the user can load it using:
+<syntaxHighlight lang=console>
+$ sudo modprobe yourmodulename
+</syntaxHighlight>
+or unload it using
+<syntaxHighlight lang=console>
+$ sudo modprobe -r yourmodulename
+</syntaxHighlight>
+However, if you want to autoload your module at startup in stage 2, you need to do:
+<syntaxHighlight lang=nix>
+boot.kernelModules = [ "yourmodulename" ];
+</syntaxHighlight>
+and the module will be automatically loaded after a reboot. If you want instead to load it at stage 1 (before the root is even mounted), you need to add it to `boot.initrd.availableKernelModules` and `boot.initrd.kernelModules`.
+Note that if you don't reboot, you can still load manually the module using `modprobe yourmodulename`, and to automatically enable a module during configuration switch/reboot, you can put `modprobe yourmodulename || true` inside the script of a systemctl service (it is for example what does wireguard).
+Finally, if you want to define some options by default (used when you load manually a module using `modprobe`, or when the system boots), you can specify them in:
+<syntaxHighlight lang=nix>
+boot.extraModprobeConfig = ''
+  options yourmodulename optionA=valueA optionB=valueB
+'';
 </syntaxHighlight>