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Merge pull request #2108 from SvenDowideit/update-the-kernel-module-docs
We don't use the Ubuntu kernels and DKMS anymore
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Sven Dowideit
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d8bba34a87
@ -46,7 +46,7 @@ By default, RancherOS ships with the kernel provided by the [os-kernel repositor
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...
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```
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`build.tar.gz` contains build headers to build additional modules (e.g. using DKMS): it is a subset of the kernel sources tarball. These files will be installed into `/usr/src/<os-kernel-tag>` using the `kernel-headers-system-docker` and `kernel-headers` services.
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`build.tar.gz` contains build headers to build additional modules: it is a subset of the kernel sources tarball. These files will be installed into `/usr/src/<os-kernel-tag>` using the `kernel-headers-system-docker` and `kernel-headers` services.
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`extra.tar.gz` contains extra modules and firmware for your kernel and should be built into a `kernel-extras` service:
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@ -1,140 +1,86 @@
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---
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title: DKMS / Loadable Kernel Modules in RancherOS
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title: Extra Kernel Modules for RancherOS
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---
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## Dynamic Kernel Module Support (DKMS) / Loadable Kernel Modules (LKM)
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Since RancherOS v0.8, we build our own kernels using an unmodified kernel.org LTS kernel.
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We also build almost all optional extras as modules - so most in-tree modules are available
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in the `kernel-extras` service.
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To compile any Kernel Modules, you first need to [deploy the Kernel Headers]({{page.osbaseurl}}/configuration/kernel-modules-kernel-headers/).
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### DKMS
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If you do need to build kernel modules for RancherOS, there are 3 options:
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DKMS is supported by running the DKMS scripts inside a *privileged* container.
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0 Try the `kernel-extras` service
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1 Ask us to add it into the next release
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2 If its out of tree, copy the methods used for the zfs and open-iscsi services
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3 Build it yourself.
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> To deploy containers that compiles DKMS modules, you will need to ensure that you bind-mount `/usr/src` and `/lib/modules`.
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## Try the kernel-extras service
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> To deploy containers that run any DKMS operations (i.e., `modprobe`), you will need to ensure that you bind-mount `/lib/modules`.
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We build the RancherOS kernel with most of the optional drivers as kernel modules, packaged
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into an optional RancherOS service.
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By default, the `/lib/modules` folder is already available in the console deployed via [RancherOS System Services]({{page.osbaseurl}}/system-services/built-in-system-services/), but not `/usr/src`. You will likely need to [deploy your own container](#docker-example) for compilation purposes.
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To install these, run:
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To learn more about Docker's privileged mode, or to limit capabilities, please review the [Docker Runtime privilege and Linux capabilities documentation](https://docs.docker.com/engine/reference/run/#/runtime-privilege-and-linux-capabilities).
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#### cloud-config Example
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```yaml
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myservice:
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image: ...
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privileged: true
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volumes:
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- /lib/modules:/lib/modules
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- /usr/src:/usr/src
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```
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#### Docker Example
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> For one-off operations, it's useful to use `--rm` to clean up containers when operations complete.
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```bash
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$ sudo system-docker run -it --rm --name dkms-install -v /usr/src:/usr/src -v /lib/modules:/lib/modules ubuntu sh -c 'apt-get update && apt-get install -y sysdig-dkms'
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```
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The same approach can be utilized with the User Docker Daemon, just replace `sudo system-docker` with `docker`.
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### LKM Dependencies
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In some situations, another Kernel Module might need loading prior to any module you're trying to add.
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In this example, we'll reference the `v4l2loopback` DKMS module, which requires probing `videodev` into the Kernel space and is not on any filesystem by default.
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First, you must enable `kernel-extras`, then `modprobe` your dependencies and subsequent modules:
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```bash
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sudo ros service enable kernel-extras
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sudo ros service up -d kernel-extras
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sudo ros service up kernel-extras
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```
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This will overlay all the compiled modules into `/lib/modules/$(uname -r)` that are configured in the default RancherOS Kernel config.
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The modules should now be available for you to `modprobe`
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Now you are ready to add your Modules into the Kernel space:
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## Ask us to do it
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```bash
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sudo modprobe videodev
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sudo modprobe v4l2loopback
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Open a GitHub issue in the https://github.com/rancher/os repository - we'll probably add
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it to the kernel-extras next time we build a kernel. Tell us if you need the module at initial
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configuration or boot, and we can add it to the default kernel modules.
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## Copy the out of tree build method
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See https://github.com/rancher/os-services/blob/master/o/open-zfs.yml and
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https://github.com/rancher/os-services/tree/master/images/20-zfs
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The build container and build.sh script build the source, and then create a tools image, which is used to
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"wonka.sh" import those tools into the console container using `docker run`
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## Build your own.
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As an example I'm going build the `intel-ishtp` hid driver using the `rancher/os-zfs:<version>` images to build in, as they should contain the right tools versions for that kernel.
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```
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sudo docker run --rm -it --privileged -v $(pwd):/data -w /data rancher/os-zfs:$(ros -v | cut -d ' ' -f 3) bash
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apt-get update
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apt-get install -qy libncurses5-dev bc libssh-dev
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curl -SsL -o src.tgz https://github.com/rancher/os-kernel/releases/download/v$(uname -r)/linux-$(uname -r)-src.tgz
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tar zxvf src/tgz
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zcat /proc/config.gz >.config
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# Yes, ignore the name of the directory :/
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cd v*
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# enable whatever modules you want to add.
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make menuconfig
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# I finally found an Intel sound hub that wasn't enabled yet
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# CONFIG_INTEL_ISH_HID=m
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make modules SUBDIRS=drivers/hid/intel-ish-hid
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# test it
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insmod drivers/hid/intel-ish-hid/intel-ishtp.ko
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rmmod intel-ishtp
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# install it
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cp drivers/hid/intel-ish-hid/*.ko /lib/modules/4.9.45-rancher/kernel/drivers/hid/
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depmod
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# done
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exit
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```
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To see which modules are pre-built, you can either do a listing of all `.ko` (kernel object) files, or review the Kernel config:
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Then in your console, you should be able to run
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```bash
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find /lib*/modules/$(uname -r) -name *.ko | less
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#or
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zcat /proc/config.gz | less
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```
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modprobe intel-ishtp
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```
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For more information regarding modifying the Kernel, please review the [Custom Kernels]({{page.osbaseurl}}/custom-builds/custom-kernels/) documentation.
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### Auto-Loading Modules
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Kernel Modules can be automatically loaded with the `rancher.modules` cloud-config field.
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```yaml
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#cloud-config
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rancher:
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modules: [btrfs]
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```
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This functionality is also available via a kernel parameter. For example, the btrfs module could be automatically loaded with `rancher.modules=[btrfs]` as a kernel parameter.
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### Ubuntu-based Kernel Manipulation
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For images that are or derive from Ubuntu, you will need some small packages for `depmod`(`kmod`) and `modprobe`(`module-init-tools`):
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```bash
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sudo apt-get install kmod module-init-tools
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```
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Most packages should already list these as dependencies in Aptitude, as well as `gcc` and related libs for packages that require compilation (which is most).
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### Troubleshooting
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Messing around with the Kernel can be tricky, so here's some common issues:
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#### kernel source for this kernel does not seem to be installed.
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Simply put, the Kernel Headers (or Source) cannot be found; enable them via the [Kernel Headers System Service]({{page.osbaseurl}}/configuration/kernel-modules-kernel-headers/).
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#### Operation not Permitted
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When inside a container, you might see similar to the following:
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```
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modprobe: ERROR: could not insert 'videodev': Operation not permitted
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```
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This is in reference to your container's privileges, not your user (i.e., `sudo` will not fix this).
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Instead, ensure you started the container with `--privileged` or the `cloud-config` setting described above.
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#### modprobe: ERROR: could not insert 'v4l2loopback': Unknown symbol in module, or unknown parameter (see dmesg)
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Again, using `v4l2loopback` as an example, but this can happen for any module.
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As stated, check out `dmesg` to see what the issue is. Chances are you'll see something like the following:
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```bash
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[ 322.734052] v4l2loopback: module verification failed: signature and/or required key missing - tainting kernel
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[ 322.734141] v4l2loopback: Unknown symbol video_ioctl2 (err 0)
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[ 322.734454] v4l2loopback: Unknown symbol v4l2_ctrl_handler_init_class (err 0)
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[ 322.734526] v4l2loopback: Unknown symbol video_devdata (err 0)
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[ 322.734563] v4l2loopback: Unknown symbol v4l2_ctrl_new_custom (err 0)
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[ 322.734599] v4l2loopback: Unknown symbol video_unregister_device (err 0)
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[ 322.734635] v4l2loopback: Unknown symbol video_device_alloc (err 0)
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[ 322.734696] v4l2loopback: Unknown symbol v4l2_device_register (err 0)
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[ 322.734732] v4l2loopback: Unknown symbol __video_register_device (err 0)
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[ 322.734765] v4l2loopback: Unknown symbol v4l2_ctrl_handler_free (err 0)
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[ 322.734796] v4l2loopback: Unknown symbol v4l2_device_unregister (err 0)
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[ 322.734828] v4l2loopback: Unknown symbol video_device_release (err 0)
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```
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This one can be trickier to evaluate, so start searching Google for symbol names to figure out which modules they derive from.
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In this example, `video_ioctl2` comes from `videodev` and can be simply inserted via the `kernel-extras` overlay described above.
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@ -90,7 +90,7 @@ By default, RancherOS ships with the kernel provided by the [os-kernel repositor
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...
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```
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`build.tar.gz` contains build headers to build additional modules (e.g. using DKMS): it is a subset of the kernel sources tarball. These files will be installed into `/usr/src/<os-kernel-tag>` using the `kernel-headers-system-docker` and `kernel-headers` services.
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`build.tar.gz` contains build headers to build additional modules: it is a subset of the kernel sources tarball. These files will be installed into `/usr/src/<os-kernel-tag>` using the `kernel-headers-system-docker` and `kernel-headers` services.
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`extra.tar.gz` contains extra modules and firmware for your kernel and should be built into a `kernel-extras` service:
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