Package NotesThis chapter contains information about how to use and maintain
the Nix expressions for a number of specific packages, such as the
Linux kernel or X.org.Linux kernelThe Nix expressions to build the Linux kernel are in pkgs/os-specific/linux/kernel.The function that builds the kernel has an argument
kernelPatches which should be a list of
{name, patch, extraConfig} attribute sets, where
name is the name of the patch (which is included in
the kernel’s meta.description attribute),
patch is the patch itself (possibly compressed),
and extraConfig (optional) is a string specifying
extra options to be concatenated to the kernel configuration file
(.config).The kernel derivation exports an attribute
features specifying whether optional functionality
is or isn’t enabled. This is used in NixOS to implement
kernel-specific behaviour. For instance, if the kernel has the
iwlwifi feature (i.e. has built-in support for
Intel wireless chipsets), then NixOS doesn’t have to build the
external iwlwifi package:
modulesTree = [kernel]
++ pkgs.lib.optional (!kernel.features ? iwlwifi) kernelPackages.iwlwifi
++ ...;
How to add a new (major) version of the Linux kernel to Nixpkgs:
Copy (svn cp) the old Nix expression
(e.g. linux-2.6.21.nix) to the new one
(e.g. linux-2.6.22.nix) and update it.Add the new kernel to all-packages.nix
(e.g., create an attribute
kernel_2_6_22).Now we’re going to update the kernel configuration. First
unpack the kernel. Then for each supported platform
(i686, x86_64,
uml) do the following:
Make an svn copy from the old
config (e.g. config-2.6.21-i686-smp) to
the new one
(e.g. config-2.6.22-i686-smp).Copy the config file for this platform
(e.g. config-2.6.22-i686-smp) to
.config in the kernel source tree.
Run make oldconfig
ARCH={i386,x86_64,um}
and answer all questions. (For the uml configuration, also
add SHELL=bash.) Make sure to keep the
configuration consistent between platforms (i.e. don’t
enable some feature on i686 and disable
it on x86_64).
If needed you can also run make
menuconfig:
$ nix-env -i ncurses
$ export NIX_CFLAGS_LINK=-lncurses
$ make menuconfig ARCH=archMake sure that
CONFIG_FB_TILEBLITTING is not
set (otherwise fbsplash won't
work). This option has a tendency to be enabled as a
side-effect of other options. If it is, investigate why
(there's probably another option that forces it to be on)
and fix it.Copy .config over the new config
file (e.g. config-2.6.22-i686-smp).Test building the kernel: nix-build -A
kernel_2_6_22. If it compiles, ship it! For extra
credit, try booting NixOS with it.It may be that the new kernel requires updating the external
kernel modules and kernel-dependent packages listed in the
kernelPackagesFor function in
all-packages.nix (such as the NVIDIA drivers,
AUFS, splashutils, etc.). If the updated packages aren’t
backwards compatible with older kernels, you need to keep the
older versions and use some conditionals. For example, new
kernels require splashutils 1.5 while old kernel require 1.3, so
kernelPackagesFor says:
splashutils =
if kernel.features ? fbSplash then splashutils_13 else
if kernel.features ? fbConDecor then splashutils_15 else
null;
splashutils_13 = ...;
splashutils_15 = ...;X.orgThe Nix expressions for the X.org packages reside in
pkgs/servers/x11/xorg/default.nix. This file is
automatically generated from lists of tarballs in an X.org
release. As such it should not be modified directly; rather, you
should modify the lists or the generator script.The generator is invoked as follows:
$ cd pkgs/servers/x11/xorg
$ cat tarballs-7.4.list extra.list old.list \
| perl ./generate-expr-from-tarballs.pl
For each of the tarballs in the .list files, the
script downloads it, unpacks it, and searches its
configure.ac and *.pc.in
files for dependencies. This information is used to generate
default.nix. The generator caches downloaded
tarballs between runs. Pay close attention to the NOT FOUND:
name messages at the end of the
run, since they may indicate missing dependencies. (Some might be
optional dependencies, however.)A file like tarballs-7.4.list contains all
tarballs in a X.org release. It can be generated like this:
$ export i="mirror://xorg/X11R7.4/src/everything/"
$ cat $(PRINT_PATH=1 nix-prefetch-url $i | tail -n 1) \
| perl -e 'while (<>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'i'}$2\n"; }; }' \
| sort > tarballs-7.4.list
extra.list contains libraries that aren’t part of
X.org proper, but are closely related to it, such as
libxcb. old.list contains
some packages that were removed from X.org, but are still needed by
some people or by other packages (such as
imake).If the expression for a package requires derivation attributes
that the generator cannot figure out automatically (say,
patches or a postInstall hook),
you should modify the generator script
(generate-expr-from-tarballs.pl).Gnome* Expression is auto-generated* How to updateGCC…