Linux Kernel: Difference between revisions
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== | == Managing Kernel Modules == | ||
<blockquote> | |||
<source lang="bash"> | <source lang="bash"> | ||
lsmod # list loaded kernel modules | lsmod # list loaded kernel modules | ||
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cat /lib/modules/$(uname -r)/modules.builtin # list builtin kernel modules | cat /lib/modules/$(uname -r)/modules.builtin # list builtin kernel modules | ||
</source> | </source> | ||
</blockquote><!-- Managing Kernel Modules --> | |||
== automatically loading kernel modules == | == automatically loading kernel modules == | ||
<blockquote> | |||
Similar to other systemd files, you can gather a bunch of kernel modules in a single file. | Similar to other systemd files, you can gather a bunch of kernel modules in a single file. | ||
The syntax of the file is a newline separated list of modules. Their names will be exactly | The syntax of the file is a newline separated list of modules. Their names will be exactly | ||
| Line 64: | Line 67: | ||
btusb | btusb | ||
</source> | </source> | ||
</blockquote><!-- automatically loading kernel modules --> | |||
</blockquote><!-- Kernel Modules --> | |||
= | = Dynamic Kernel Modules (DKMS) = | ||
< | <blockquote> | ||
DKMS packages include kernel modules that are recompiled every time a new kernel is installed.<br> | |||
< | You can safely install/build these modules after an update without reboot, but you'll need to restart to use them (so the new kernel is used). | ||
</blockquote><!-- Kernel Modules --> | </blockquote><!-- Dynamic Kernel Modules (DKMS) --> | ||
= Kernel Downgrades = | = Kernel Downgrades = | ||
<blockquote> | <blockquote> | ||
Boot your distro off a USB stick, and chroot into your existing installation. | Boot your distro off a USB stick, and chroot into your existing installation. | ||
You'll need to uninstall all packages that are particular to your kernel version | You'll need to uninstall all packages that are particular to your kernel version | ||
like linux, linux-headers, virtualbox-host-modules, virtualbox-guest-modules. | like linux, linux-headers, virtualbox-host-modules, virtualbox-guest-modules. | ||
Revision as of 15:42, 14 May 2022
Documentation
kernel option docs https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html tut: kernel programming guide https://sysprog21.github.io/lkmpg/
Locations
/etc/modprobe.d/*.confload kernel modules on startup /lib/modules/$(uname -r)/*kernel modules (modules.builtin lists builtin modules)
Kernel Options
Your can add boot options for your kernel.
The location depends on your bootloader, forsystemd-bootit would be in a file like/boot/loader/entries/archlinux.conf.# /boot/loader/entries/archlinux.conf # ... options rdblacklist=nouveau nofb nomodesetSome useful kernel options
nofb # disable framebuffer nomodeset # disable kernel modesetting (increased resolution)
Kernel Modules
/etc/modprobe.d/*.conflocation of kernel-module files Managing Kernel Modules
lsmod # list loaded kernel modules modinfo btusb # list kernel options for btusb modprobe btusb # load 'btusb' kernel module cat /lib/modules/$(uname -r)/modules.builtin # list builtin kernel modulesautomatically loading kernel modules
Similar to other systemd files, you can gather a bunch of kernel modules in a single file. The syntax of the file is a newline separated list of modules. Their names will be exactly as they would be called by modprobe. A newline with a first character of '#', marks a comment.
/etc/modprobe.d/wiimote.conf
# /etc/modprobe.d/{yourname}.conf uinput btusb
Dynamic Kernel Modules (DKMS)
DKMS packages include kernel modules that are recompiled every time a new kernel is installed.
You can safely install/build these modules after an update without reboot, but you'll need to restart to use them (so the new kernel is used).
Kernel Downgrades
Boot your distro off a USB stick, and chroot into your existing installation. You'll need to uninstall all packages that are particular to your kernel version like linux, linux-headers, virtualbox-host-modules, virtualbox-guest-modules.
# Connect to the internet sudo mount /dev/sda2 /mnt arch-chroot /mnt /bin/bash cd /var/cache/pacman/pkg pacman -Rs linux-3.9.7 linux-headers-3.9.7 virtualbox-host-modules virtualbox-guest-modules pacman -U linux-3.7.1 linux-headers 3.7.1 exit sudo reboot
