kernelconfig 0.3.3

Generate custom Linux kernel configurations from curated sources

Generate custom Linux kernel configurations from curated sources.

(Note. kernelconfig is a port to python of a previously privately-only released tool called genconfig. The latter, before it died a horrible death at 5400rpm or so, had much more advanced features, but these will be re-introduced progressively. Error handling is currently mostly taken care of by python, so, although it won’t send you off track, error messages may look a bit cryptic at times. This too will be improved.)

Introduction

TL;DR Compiling a kernel is easy, configuring it not so much. Unless you have the time and skill to follow kernel development, it is best to leave that to a team of specialists. But where to download up to date configurations? What to do if you need to do the same changes over and over with each new version? Enter kernelconfig. It will automatically download a base configuration matching the kernel you want to compile from a curated source of your choice (Debian, Ubuntu, Fedora, Liquorix, etc…), customize it with a number of options which suit your taste and needs, apply macros to set a number of options in a smart way, and more.

You can do that, for example, from within the kernel sources directory:

$ kernelconfig

and it will automatically generate the .config file for you, using the default settings (see below). No questions asked.

If you are not in the kernel sources directory and these are located in ‘/usr/src/linux-4.2’:

$ kernelconfig -k /usr/src/linux-4.2

In case the curated source in your settings does not have a base configuration for kernel version 4.2 but has one for version 4.1:

$ kernelconfig -k /usr/src/linux-4.2 -v 4.1

Expect to have to answer some questions if/when you run ‘make oldconfig’ before compiling your kernel.

Finally, if you are going to cross-compile a kernel for arm:

$ kernelconfig --arch arm

Here is a simple example of a settings file:

[source]
ubuntu --lowlatency

[options]
disable MODULE_SIG
enable BLK_DEV_SD SATA_AHCI
enable BTRFS_FS
module EVBUG

This will automatically download a version-matching Ubuntu configuration with low-latency options, disable verification of module signatures, build the SCSI disk and SATA AHCI drivers into the kernel (i.e., not as modules) to be able to boot without an initramfs, and also build the BTRFS driver into the kernel for the same reason. Finally, we make sure EVBUG is compiled as a module to only load it when necessary since it will pollute the system log. This will be done consistently and automatically every time you will need to compile a new kernel. All that with the comfort of a whole team of upstream developers handling the grunt work for you. As Tom and Ray Magliozzi like(d) to say: “Pretty cute, huh?”

If you are the kind of perverted individual who likes reading manuals, then read on. If not, get used to being mocked.

Installing kernelconfig

The best way is, if possible, to rely on your distribution’s package manager.

You will need the following python 3 packages: docutils, lxml and version 4 or later of BeautifulSoup. Depending on your distribution, these can also be called python-beautifulsoup, python3-bs4, python-lxml, python3-lxml, python3-docutils, etc… Make sure you only get python 3 packages as kernelconfig is not compatible with python 2.

You can install from PyPI using pip. For example, as root:

$ pip3 install kernelconfig

The default settings file and examples will be installed into ‘/etc/kernelconfig’.

Whether root or not, it is possible to make a user installation, like this:

$ pip3 install --user kernelconfig

In this case, the default settings file and examples will be installed into ‘~/.config/kernelconfig’.

Optional arguments

• -h, –help

  Show the help message and exit.

• -a ARCH, –arch ARCH

  Force the kernel configuration architecture. ARCH is as returned by ‘uname -m’. Useful for cross-compiling.

• -k KERNEL, –kernel KERNEL

  Path to the unpacked kernel sources directory. It can be absolute or relative to the current working directory. The default is ‘.’, the current working directory.

• -s SETTINGS, –settings SETTINGS

  Path to the settings file. It can be an absolute or user-expandable path to an arbitrary file. If it is a relative path, then the file will be searched for relatively to ~/.config/kernelconfig first and then /etc/kernelconfig. Sub-directories relative to both these locations can be used. If a path relative to the current working directory is desired, prefix it with ‘./’. The default is ‘default’, i.e., ‘~/.config/kernelconfig/default’ if it exists, or, failing that, ‘/etc/kernelconfig/default’.

• -v VERSION, –version VERSION

  Force the kernel configuration version. Useful when there is no matching major kernel version in the curated source.

Settings syntax

A comment line starts with a ‘#’ as its first character.

Lines can be empty. There is no limit as to how many consecutive empty lines there can be.

[source] section

Lines other than the first non-empty and non-comment line will be discarded.

A source is the name of an executable in either ‘/usr/share/kernelconfig’ or ‘~/.local/share/kernelconfig’, depending on the instalation being of the –user type or not, possibly followed by a number of optional arguments. For example:

liquorix --pae

or:

ubuntu --lowlatency

See “Curated sources” below for a list of supported sources and optional arguments.

[options] section

A list of one action per line followed by one or more kernel options to perform the action on. No indentation is allowed, but empty and comment lines are possible.

Actions:

• enable: enable the option in the kernel, not as module. For example:

  enable BLK_SD_DEV SATA_AHCI

  Build the BLK_SD_DEV and ATA_AHCI drivers into the kernel so that it is bootable without the need for an initramfs.

• module: enable the option as module only so as to be able to only load it when desired. For example:

  module EVBUG

  The EVBUG driver is available to load for debugging when necessary.

• disable: disable the option entirely. For example:

  disable MODULE_SIG

  Disable module signature verification.

• set: set an option to a given value. For example:

  set DEFAULT_IOSCHED="bfq"

  Use Budget Fair Queueing as the default I/O scheduler.

Note 1. Do not prefix options names with ‘CONFIG_’. kernelconfig takes care of that for you.

Note 2. Option names will always be capitalized for you if you don’t. It is however easier to read a settings file whose options are capitalized.

Curated sources

Here is a list of the currently supported curated sources. More will come.

Liquorix

• Name in settings: liquorix

• Supported architectures: i386, i686, x86_64

• Options:

  • –pae: enable Physical Address Extension on processors supporting it to extend physical address space 4GB (i386 and i686 only).

Ubuntu

• Name in settings: ubuntu

• Supported architectures: i386, i686, x86_64 (upstream supports more, will come later)

• Options:

  • –lowlatency: enable low-latency timing and preemption options.

TODO

• Add better error checking and feedback

• Add sources: defconfig, fedora, centos, debian, genkernel, etc…

• Centralize functions necessary to multiple sources

• Add macros, parameterized macros, conditional macros

• Autodetect hardware

• Integrate with genkernel

Author

Please send comments, patches, flowers and insults to Denis Dupeyron <[e-mail]>