Modules support — am I doing this right?

[intelfx]

(Someone pointed me at virtme-ng just today, so I'm not entirely familiar with how it works, apologies.)

Let's say that instead of using virtme-ng to build a fresh new minimal kernel, I have an already configured and built kernel tree in $PWD with a full distro config, modules and everything. I want to run that kernel with full support for in-tree and out-of-tree modules (dkms, ...) alike.

I didn't see an option to specifically point vng at a built kernel tree. According to the help, it's either vng -b to build in $PWD, or vng -r /path/to/bzImage/or/dir to run a standalone binary. So I just ran vng -r ., and it seemed to autodiscover the modules and do the right thing, even with a /lib/modules/$(uname -r)/build symlink back to the source tree.

Is it actually supported to run vng like that (i.e. point --run at a built kernel tree and expect that it will grab not just the kernel binary but also the modules and headers) or is it all just a happy coincidence?

[arighi]

vng is automatically using the modules from the build dir, basically it installs all the modules in your target kernel build dir ($PWD in this case) in .virtme_mods/ and it will bind mount this dir in /lib/modules/$kernel_version, so inside the vng session you'll be able to load external modules normally.

Keep in mind that this will replace the original /lib/modules/$kernel_version on the host, so if you have out-of-tree dkms modules you won't be able to see them with your recompiled kernel. But you can see them if you run the host's kernel (using vng -r).

Also note that vng -r . is equivalent to simply running vng (default is to run the kernel from the current working dir).

[intelfx]

So if the argument to -r (or the implied -r .) points to a build tree, vng is supposed to not just discover the kernel binary (as described in the help), but also discover the built modules and do the right thing™?

[arighi]

Correct, it's supposed to be smart enough to detect both the kernel binary, the corresponding modules and do the right thing(tm) - most of the times. :)