Arch linux modules directory

Kernel module

Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system.

To create a kernel module, you can read The Linux Kernel Module Programming Guide. A module can be configured as built-in or loadable. To dynamically load or remove a module, it has to be configured as a loadable module in the kernel configuration (the line related to the module will therefore display the letter M ).

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Obtaining information

Modules are stored in /usr/lib/modules/kernel_release . You can use the command uname -r to get your current kernel release version.

To show what kernel modules are currently loaded:

To show information about a module:

To list the options that are set for a loaded module:

To display the comprehensive configuration of all the modules:

To display the configuration of a particular module:

List the dependencies of a module (or alias), including the module itself:

Automatic module loading with systemd

Today, all necessary modules loading is handled automatically by udev, so if you do not need to use any out-of-tree kernel modules, there is no need to put modules that should be loaded at boot in any configuration file. However, there are cases where you might want to load an extra module during the boot process, or blacklist another one for your computer to function properly.

Kernel modules can be explicitly listed in files under /etc/modules-load.d/ for systemd to load them during boot. Each configuration file is named in the style of /etc/modules-load.d/program.conf . Configuration files simply contain a list of kernel modules names to load, separated by newlines. Empty lines and lines whose first non-whitespace character is # or ; are ignored.

See modules-load.d(5) for more details.

Manual module handling

Kernel modules are handled by tools provided by kmod package. You can use these tools manually.

To load a module:

To load a module by filename (i.e. one that is not installed in /usr/lib/modules/$(uname -r)/ ):

To unload a module:

Setting module options

To pass a parameter to a kernel module, you can pass them manually with modprobe or assure certain parameters are always applied using a modprobe configuration file or by using the kernel command line.

Manually at load time using modprobe

The basic way to pass parameters to a module is using the modprobe command. Parameters are specified on command line using simple key=value assignments:

Using files in /etc/modprobe.d/

Files in /etc/modprobe.d/ directory can be used to pass module settings to udev, which will use modprobe to manage the loading of the modules during system boot. Configuration files in this directory can have any name, given that they end with the .conf extension. The syntax is:

Using kernel command line

If the module is built into the kernel, you can also pass options to the module using the kernel command line. For all common bootloaders, the following syntax is correct:

Simply add this to your bootloader’s kernel-line, as described in Kernel Parameters.

Aliasing

Aliases are alternate names for a module. For example: alias my-mod really_long_modulename means you can use modprobe my-mod instead of modprobe really_long_modulename . You can also use shell-style wildcards, so alias my-mod* really_long_modulename means that modprobe my-mod-something has the same effect. Create an alias:

Some modules have aliases which are used to automatically load them when they are needed by an application. Disabling these aliases can prevent automatic loading but will still allow the modules to be manually loaded.

Blacklisting

Blacklisting, in the context of kernel modules, is a mechanism to prevent the kernel module from loading. This could be useful if, for example, the associated hardware is not needed, or if loading that module causes problems: for instance there may be two kernel modules that try to control the same piece of hardware, and loading them together would result in a conflict.

Some modules are loaded as part of the initramfs. mkinitcpio -M will print out all automatically detected modules: to prevent the initramfs from loading some of those modules, blacklist them in a .conf file under /etc/modprobe.d and it shall be added in by the modconf hook during image generation. Running mkinitcpio -v will list all modules pulled in by the various hooks (e.g. filesystems hook, block hook, etc.). Remember to add that .conf file to the FILES array in /etc/mkinitcpio.conf if you do not have the modconf hook in your HOOKS array (e.g. you have deviated from the default configuration), and once you have blacklisted the modules regenerate the initramfs, and reboot afterwards.

Using files in /etc/modprobe.d/

Create a .conf file inside /etc/modprobe.d/ and append a line for each module you want to blacklist, using the blacklist keyword. If for example you want to prevent the pcspkr module from loading:

However, there is a workaround for this behaviour; the install command instructs modprobe to run a custom command instead of inserting the module in the kernel as normal, so you can force the module to always fail loading with:

This will effectively blacklist that module and any other that depends on it.

Using kernel command line

You can also blacklist modules from the bootloader.

Simply add module_blacklist=modname1,modname2,modname3 to your bootloader’s kernel line, as described in Kernel parameters.

Troubleshooting

Modules do not load

In case a specific module does not load and the boot log (accessible by running journalctl -b as root) says that the module is blacklisted, but the directory /etc/modprobe.d/ does not show a corresponding entry, check another modprobe source folder at /usr/lib/modprobe.d/ for blacklisting entries.

A module will not be loaded if the «vermagic» string contained within the kernel module does not match the value of the currently running kernel. If it is known that the module is compatible with the current running kernel the «vermagic» check can be ignored with modprobe —force-vermagic .

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Dynamic Kernel Module Support

Dynamic Kernel Module Support (DKMS) is a program/framework that enables generating Linux kernel modules whose sources generally reside outside the kernel source tree. The concept is to have DKMS modules automatically rebuilt when a new kernel is installed.

This means that a user does not have to wait for a company, project, or package maintainer to release a new version of the module. Since the introduction of pacman hooks, the rebuild of the modules is handled automatically when a kernel is upgraded.

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Installation

Install the dkms package and the headers for the target kernel/kernels. For example, for the default linux kernel this would be linux-headers . Other kernels have their own respective headers packages.

A good number of modules that lie outside the kernel source tree have a DKMS variant; a few are hosted in the official repositories, most are found in the AUR.

Upgrades

Though the rebuild of the DKMS modules is usually seamless during a kernel upgrade, it may still happen that the rebuild fails. You should pay extra attention to the pacman output. This applies in particular if the system relies on the DKMS module to boot successfully and/or if you use DKMS with a custom kernel not in the official repositories.

To deal with changes in the kernel, fix bugs, or add necessary features consider upgrading the DKMS package before rebooting.

Usage

Usage for invoking DKMS manually.

Tab-completion is available by doing:

List modules

To list the current status of modules, versions and kernels within the tree:

Rebuild modules

Rebuild all modules for the currently running kernel:

or for a specific kernel:

To build a specific module for the currently running kernel:

To build a module for all kernels:

Remove modules

To remove a module (old ones are not automatically removed):

If the package dkms is removed the information regarding previous module build files is lost. If this is the case, go through /usr/lib/modules/kernel_release and /var/lib/dkms/package_name and delete all files and directories no longer in use.

DKMS package creation

Initial ramdisk

In case you have got any kernel modules installed via DKMS that are used in initial ramdisk, e.g. zfs-dkms AUR , you may want to write a pacman hook to automate the process of regenerating initramfs image(s).

For example, when using linux and mkinitcpio, to update ZFS module after each zfs-dkms AUR upgrade,

You may add more targets to the hook and make additional copies of the hook if you have installed other kernels. Note the 90- prefix is necessary to make sure it runs after the DKMS hooks.

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Compile kernel module

Sometimes you may wish to compile Linux’s Kernel module without recompiling the whole kernel.

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Build environment

Firstly you will need to install build dependencies such as compiler ( base-devel ) and linux-headers .

Next you will need to get the source code for the kernel version the module is intended to run on. You may try use newer kernel sources but most likely compiled module will not load.

In case the intended kernel version is the installed kernel, find its version with

There are two main options to acquire the required source. Each option has slightly different usage methods and directory structure.

Traditional compilation

See Kernels/Traditional compilation#Download the kernel source. If you fetch latest source using Git you will need to checkout needed version using tag (eg. v4.1).

Arch Build System

For a general overview on Arch Build System read ABS. See Kernel/Arch Build System for acquiring the kernel source, as well as the directory structure, and other details.

Source configuration

When you have the source code, enter its directory. For the #Arch Build System case, that directory would be src/archlinux-linux/ down from where the PKGBUILD is.

The output from make help is beneficial here. Start by cleaning with

An appropriate .config file is now required. If no config file is to be seen nearby, perhaps from a saved .config , and the intended kernel version is the running kernel, you can use its configuration file:

Next ensure the .config file is adjusted for the kernel version. If you are using kernel sources for the exact current version then it should not ask anything. But for another version than the current kernel you might be asked about some options. In any case, for the #Arch Build System option, you might want to examine the PKGBUILD::prepare() function.

If the module you want to compile have some compilation options such as debug build, or it was not compiled before, you can also, possibly must, adjust the kernel configuration. You can do this with one of the many configuration targets mentioned by make help.

Module compilation

In order to compile and load our module cleanly, we must find the value of the EXTRAVERSION component of the current kernel version number so we can match the version number exactly in our kernel source. EXTRAVERSION is a variable set in the kernel top-level Makefile, but the Makefile in a vanilla kernel source will have EXTRAVERSION empty; it is set only as part of the Arch kernel build process. If relevant, the value of the current kernel’s EXTRAVERSION can be found by looking at the output of the uname -r command. In general, the kernel version is the concatenation of three components. Namely, the numeric version, the EXTRAVERSION, and the LOCALVERSION. The numeric version itself is a concatenation of three numbers. If built by a PKGBUILD file, the LOCALVERSION will be taken from the pkgrel variable, prefixed by a hyphen. And the EXTRAVERSION will be the suffix of the pkgver variable, where the period character to the right of the third numeric number of the numeric version is replaced by a hyphen. For example, with the linux package linux 5.5.8.arch1-1 , the LOCALVERSION is -1 . The EXTRAVERSION is -arch1 . The output of uname -r will be 5.5.8-arch1-1 in that example.

Once the EXTRAVERSION value is known, we prepare the source for module compilation:

Alternatively, if you are happy to load modules with modprobe using the —force-vermagic option to ignore mismatches in the kernel version number, you can simply run:

Finally, compile wanted module by specifying its directory name. You can find the module location, thus also its directory name, with modinfo or find.

As a last resort, if nothing else has worked, you can

Which will build all the modules from the kernel configuration.

out-of-tree module compilation

get the official source code of the current running linux kernel as described in Kernel/Arch Build System:

then point to the checked out source when compiling the module:

Module installation

Now after successful compilation you just need to gzip and copy it over for your current kernel.

If you are replacing some existing module you will need to overwrite it (and remember that reinstalling linux will replace it with default module)

Or alternatively, you can place the updated module in the updates folder (create it if it does not already exist).

However if you are adding a new module you can just copy it to extramodules (note, this is just example as btrfs will not get loaded from here)

You need to rebuild the module dependency tree with «depmod» to use installed modules.

If you are compiling a module for early boot (e.g. updated module) which is copied to Initramfs then you must remember to regenerate it with (otherwise your compiled module will not be loaded).

possible errors

If EXTRAVERSION is not set correctly the following errors may occur

adding force-vermagic makes it ignore the version mismatch

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Installation guide

This document is a guide for installing Arch Linux using the live system booted from an installation medium made from an official installation image. The installation medium provides accessibility features which are described on the page Install Arch Linux with accessibility options. For alternative means of installation, see Category:Installation process.

Before installing, it would be advised to view the FAQ. For conventions used in this document, see Help:Reading. In particular, code examples may contain placeholders (formatted in italics ) that must be replaced manually.

For more detailed instructions, see the respective ArchWiki articles or the various programs’ man pages, both linked from this guide. For interactive help, the IRC channel and the forums are also available.

Arch Linux should run on any x86_64-compatible machine with a minimum of 512 MiB RAM, though more memory is needed to boot the live system for installation.[1] A basic installation should take less than 2 GiB of disk space. As the installation process needs to retrieve packages from a remote repository, this guide assumes a working internet connection is available.

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Pre-installation

Acquire an installation image

Visit the Download page and, depending on how you want to boot, acquire the ISO file or a netboot image, and the respective GnuPG signature.

Verify signature

It is recommended to verify the image signature before use, especially when downloading from an HTTP mirror, where downloads are generally prone to be intercepted to serve malicious images.

On a system with GnuPG installed, do this by downloading the PGP signature (under Checksums in the Download page) to the ISO directory, and verifying it with:

Alternatively, from an existing Arch Linux installation run:

Prepare an installation medium

The installation image can be supplied to the target machine via a USB flash drive, an optical disc or a network with PXE: follow the appropriate article to prepare yourself an installation medium from the chosen image.

Boot the live environment

1. Point the current boot device to the one which has the Arch Linux installation medium. Typically it is achieved by pressing a key during the POST phase, as indicated on the splash screen. Refer to your motherboard’s manual for details.
2. When the installation medium’s boot loader menu appears, select Arch Linux install medium and press Enter to enter the installation environment.

To switch to a different console—for example, to view this guide with Lynx alongside the installation—use the Alt+arrow shortcut. To edit configuration files, mcedit(1) , nano and vim are available. See packages.x86_64 for a list of the packages included in the installation medium.

Set the console keyboard layout

The default console keymap is US. Available layouts can be listed with:

To modify the layout, append a corresponding file name to loadkeys(1) , omitting path and file extension. For example, to set a German keyboard layout:

Console fonts are located in /usr/share/kbd/consolefonts/ and can likewise be set with setfont(8) .

Verify the boot mode

To verify the boot mode, list the efivars directory:

If the command shows the directory without error, then the system is booted in UEFI mode. If the directory does not exist, the system may be booted in BIOS (or CSM) mode. If the system did not boot in the mode you desired, refer to your motherboard’s manual.

Connect to the internet

To set up a network connection in the live environment, go through the following steps:

• Ensure your network interface is listed and enabled, for example with ip-link(8) :
• For wireless and WWAN, make sure the card is not blocked with rfkill.
• Connect to the network:
  • Ethernet—plug in the cable.
  • Wi-Fi—authenticate to the wireless network using iwctl.
  • Mobile broadband modem—connect to the mobile network with the mmcli utility.
• Configure your network connection:
  • DHCP: dynamic IP address and DNS server assignment (provided by systemd-networkd and systemd-resolved) should work out of the box for Ethernet, WLAN and WWAN network interfaces.
  • Static IP address: follow Network configuration#Static IP address.
• The connection may be verified with ping:

Update the system clock

Use timedatectl(1) to ensure the system clock is accurate:

To check the service status, use timedatectl status .

Partition the disks

When recognized by the live system, disks are assigned to a block device such as /dev/sda , /dev/nvme0n1 or /dev/mmcblk0 . To identify these devices, use lsblk or fdisk.

Results ending in rom , loop or airoot may be ignored.

The following partitions are required for a chosen device:

If you want to create any stacked block devices for LVM, system encryption or RAID, do it now.

Use fdisk or parted to modify partition tables. For example:

Example layouts

BIOS with MBR

Mount point	Partition	Partition type	Suggested size
[SWAP]	/dev/swap_partition	Linux swap	More than 512 MiB
/mnt	/dev/root_partition	Linux	Remainder of the device

UEFI with GPT

Mount point	Partition	Partition type	Suggested size
/mnt/boot or /mnt/efi 1	/dev/efi_system_partition	EFI system partition	At least 260 MiB
[SWAP]	/dev/swap_partition	Linux swap	More than 512 MiB
/mnt	/dev/root_partition	Linux x86-64 root (/)	Remainder of the device

1. /mnt/efi should only be considered if the used boot loader is capable of loading the kernel and initramfs images from the root volume. See the warning in Arch boot process#Boot loader.

Format the partitions

Once the partitions have been created, each newly created partition must be formatted with an appropriate file system. For example, to create an Ext4 file system on /dev/root_partition , run:

If you created a partition for swap, initialize it with mkswap(8) :

Mount the file systems

Mount the root volume to /mnt . For example, if the root volume is /dev/root_partition :

Create any remaining mount points (such as /mnt/efi ) using mkdir(1) and mount their corresponding volumes.

If you created a swap volume, enable it with swapon(8) :

genfstab(8) will later detect mounted file systems and swap space.

Installation

Select the mirrors

Packages to be installed must be downloaded from mirror servers, which are defined in /etc/pacman.d/mirrorlist . On the live system, after connecting to the internet, reflector updates the mirror list by choosing 20 most recently synchronized HTTPS mirrors and sorting them by download rate.[2]

The higher a mirror is placed in the list, the more priority it is given when downloading a package. You may want to inspect the file to see if it is satisfactory. If it is not, edit the file accordingly, and move the geographically closest mirrors to the top of the list, although other criteria should be taken into account.

This file will later be copied to the new system by pacstrap, so it is worth getting right.

Install essential packages

Use the pacstrap(8) script to install the base package, Linux kernel and firmware for common hardware:

The base package does not include all tools from the live installation, so installing other packages may be necessary for a fully functional base system. In particular, consider installing:

• userspace utilities for the management of file systems that will be used on the system,
• utilities for accessing RAID or LVM partitions,
• specific firmware for other devices not included in linux-firmware (e.g. sof-firmware for sound cards),
• software necessary for networking,
• a text editor,
• packages for accessing documentation in man and info pages: man-db , man-pages and texinfo .

To install other packages or package groups, append the names to the pacstrap command above (space separated) or use pacman while chrooted into the new system. For comparison, packages available in the live system can be found in packages.x86_64.

Configure the system

Fstab

Generate an fstab file (use -U or -L to define by UUID or labels, respectively):

Check the resulting /mnt/etc/fstab file, and edit it in case of errors.

Chroot

Change root into the new system:

Time zone

Run hwclock(8) to generate /etc/adjtime :

This command assumes the hardware clock is set to UTC. See System time#Time standard for details.

Localization

Edit /etc/locale.gen and uncomment en_US.UTF-8 UTF-8 and other needed locales. Generate the locales by running:

Network configuration

Add matching entries to hosts(5) :

If the system has a permanent IP address or a fully qualified domain name, see the example in Network configuration#Local hostname resolution.

Complete the network configuration for the newly installed environment, that may include installing suitable network management software.

Initramfs

Creating a new initramfs is usually not required, because mkinitcpio was run on installation of the kernel package with pacstrap.

For LVM, system encryption or RAID, modify mkinitcpio.conf(5) and recreate the initramfs image:

Root password

Boot loader

Choose and install a Linux-capable boot loader. If you have an Intel or AMD CPU, enable microcode updates in addition.

Reboot

Exit the chroot environment by typing exit or pressing Ctrl+d .

Optionally manually unmount all the partitions with umount -R /mnt : this allows noticing any «busy» partitions, and finding the cause with fuser(1) .

Finally, restart the machine by typing reboot : any partitions still mounted will be automatically unmounted by systemd. Remember to remove the installation medium and then login into the new system with the root account.

Post-installation

See General recommendations for system management directions and post-installation tutorials (like creating unprivileged user accounts, setting up a graphical user interface, sound or a touchpad).

For a list of applications that may be of interest, see List of applications.

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