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= Linux/RTAI debian package builder

This is a big clumsy system for building debian packages of the Linux
kernel patched with RTAI, and the RTAI userspace.

It is inspired by John Morris' similar build system.

At the top level (the repo you're looking at right now) there's a Makefile
that knows how to fetch various hacked upstream sources and build debs
from them.

This Makefile does all building inside pbuilder chroots.

The things it fetches and builds are:

    * linux (tarball from kernel.org, debian/ directory from seb's repo
        based on debian.org's linux.git repo)

    * linux-tools (used for building out-of-tree kernel modules, we use
        a specific version of debian.org's package, plus some minor
        tweaks)

    * kmod (manages kernel modules)

    * rtai (based on the ShabbyX repo, but a special branch that adds
        debian packaging)


= Using this system to build Linux/RTAI

First build kernel-wedge and kmod (needed to build the kernel on Precise).
This step is needed the first time only.

-----
make kernel-wedge.deb
make kmod.deb
-----

Then build the linux kernel.  This uses the kernel.org tarball, with
packaging provided by a local git repo based on Debian's packaging of
the linux kernel.  Our local debian packaging of the linux kernel adds
the rtai patch and not much else.

-----
make linux.deb
-----

Then build linux-tools.  This step is needed the first time you build
a new X.Y kernel version (for example, you need a linux-tools for 3.4,
another for 3.14, etc).

-----
make linux-tools.deb
-----

Finally build RTAI.

-----
make rtai.deb
-----


= Modifying/updating Linux or RTAI

This build system pulls together software from three different places:

* The Linux kernel, from kernel.org

* The debian packaging of the Linux kernel, from debian.org

* The RTAI kernel patch and userspace, from rtai.org

All three have to have matching versions.  The RTAI kernel patch targets
a few specific Linux kernel versions.  The debian kernel packaging is
available for lots of kernel versions.

So the process is roughly this:

* Find the RTAI kernel patch you want to use.

* Find the Debian packaging for the kernel version targetted by the RTAI
  kernel patch.


== Modifying/updating Linux

Debian now manages the kernel debian packaging in git:

----
The package repositories are available at:

git+ssh://git.debian.org/git/kernel/firmware-free.git
git+ssh://git.debian.org/git/kernel/firmware-nonfree.git
git+ssh://git.debian.org/git/kernel/linux.git
git+ssh://git.debian.org/git/kernel/linux-base.git
git+ssh://git.debian.org/git/kernel/linux-latest.git
git+ssh://git.debian.org/git/kernel/linux-tools.git

and non-packaged documentation and scripts are in:

git+ssh://git.debian.org/git/kernel/kernel-team.git
-----

The linux/linux-$(LINUX_VERSION/debian directory is a checkout of a
git branch.  The git repo is cloned and the branch checked out by make
when the debian/ directory does not exist, and is left alone otherwise.

The git repo & branch the the debian/ directory is initialized to (if
it does not exist) are configured at the top of the top-level Makefile.

The original debian/ packaging for Linux 3.4.87 with the rtai
4.0-shabby-111-g44557fc kernel patch was created from the Debian kernel
packaging repo:

    http://anonscm.debian.org/viewvc/kernel/

To access this SVN repo via git add this to your .git/config:

-----
    [svn-remote "dists-trunk"]
        url = svn://anonscm.debian.org/svn/kernel/dists/trunk/linux/debian/
        fetch = :refs/remotes/dists-trunk
-----

The original packaging was branched from r19214, which was the last
commit of the upstream packaging to support the 3.4 kernel.

Good info on working with the Debian packaging of the Linux kernel is
available in the Debian Linux Kernel Handbook:

    http://kernel-handbook.alioth.debian.org/

Also here:

    https://wiki.debian.org/HowToRebuildAnOfficialDebianKernelPackage

Building the linux kernel for Precise requires the kmod package from
Wheezy.

=== Changing the kernel config

Here are the instructions on changing kernel configs:

    http://kernel-handbook.alioth.debian.org/ch-common-tasks.html#s4.2.3

It might be easiest to do these inside pbuilder for the build dependencies
to work out right:

-----
# outside the chroot:
make linux.dsc
make pbuilder/$(DIST)/$(ARCH)/login
# copy the dsc into tmp/ in the chroot, which lives in tmp/$(PID)

# inside the chroot login:
cd /tmp
dpkg-source -x *.dsc
cd linux-*
dpkg-checkbuilddeps
# install missing build deps
apt-get install libncurses-dev
debian/rules source
make -f debian/rules.gen setup_i386_rtai_686-pae
make -C debian/build/build_i386_rtai_686-pae/ oldconfig
make -C debian/build/build_i386_rtai_686-pae/ menuconfig
-----

FIXME: That makes a new .config, i wonder how to split it up into the
various files in debian/config?  You could diff .config and .config.old
to see what settings you changed, then change those in the already-split
files?  I wonder how to choose which settings go in which files, and
what happens if a setting is in multiple files.


==  linux-tools

The linux-tools packaging is from the upstream debian packaging.

Add this to .git/config:

-----
    [svn-remote "dists-trunk"]
    url = svn://svn.debian.org/svn/kernel/dists/trunk/linux-tools/debian/
    fetch = :refs/remotes/dists-trunk
-----

The most recent commit in linux-tools dists-trunk that applies to linux
3.4 is r19111, fcdbb9d49df93aa5801157ecd0d7b4f97754f5ab, so create a
3.4 branch from that.

Cherry-picked 784d0fc795fb7b8b9f6a6186335caa171c16225c (adds .tar.xz
support).


== RTAI

I'm choosing to base my debs on the ShabbyX RTAI repo:
https://github.com/ShabbyX/RTAI.git

=== The RTAI packages in Ubuntu and Debian are no good

precise: 3.8.1
trusty: 3.9.1 (kernel patches are too old)

wheezy: 3.8.1
sid: 3.9.1

These packages provide the RTAI userspace libraries and headers as binary
debs, but provide the kernel modules only in source form.  These kernel
sources are to be built with module-assistant, but it doesn't work out
of the box for me, and i've no interest in taking this path.

=== RTAI for LinuxCNC

My old (3.4.55-rtai-2) shitty rtai kernel debs are of commit
a0dc5355ee233032926dd23d1e132ef1befbbd76.  That commit used to be in the
master branch, now it's in a branch called "old-master".  It looks like
master was rebased and that commit corresponds to 223f5d73 (in master) now.

My branch is called prerelease-7, but it doesnt work so use old-3.9-debs
instead.

A reasonable version number for it would be
"3.9-shabby-memleak-2013.12.13"

My old rtai debs were based on:

    mozmck's (jepler's?) old debianization of rtai

    make-kpkg to build the kernel deb

    My process:

        fetch the rtai git repo

        fetch the linux tarball

        apply rtai patch to linux source

        build linux debs with make-kpkg

        install linux-headers

        build rtai-modules


= Old notes to self

To add a new key to the pbuilder keyring from a key server:

    gpg --verbose --keyring pbuilder/keyring.gpg --no-default-keyring --recv-keys CBF8D6FD518E17E1

To add a new key to the pbuilder keyring from a local keyring (for
example the local archive signing key):

    gpg --armor --export 'Key Name' | gpg --verbose --keyring pbuilder/keyring.gpg --no-default-keyring --armor --import -

There's also the 'pbuilder/keyring.gpg' target in the Makefile.


apt-get install python-six

== linux

    To build all debs:

        DEB_BUILD_OPTIONS=parallel=$(($(nproc)*2)) fakeroot debian/rules binary

    To build just a particular deb:

        DEB_BUILD_OPTIONS=parallel=$(($(nproc)*2)) fakeroot make -f debian/rules.gen binary-arch_amd64_rtai   


= Open Issues


== use dput/mini-dinstall with keep_old


== Why does pbuilder re-create the dsc, but differently?

The .orig.tar.xz is the same but the other files have different md5sums.


== linux: turn off the 'none' featureset, it just wastes build time


== download all orig things into /orig, so they're easier to save on 'make clean'


== Make a new install-%-deb target, for all to use

Should this target remove any existing debs from dists/%/?  Probably not?


== rtai package fixup

The rtai-modules package is matched to a kernel version, like
'3.4-9-rtai-686-pae'.  This is reflected in the package name and
dependencies, and that's good.

It should install in a place that doesnt conflict with other versions
of itself, just like you can have multiple kernels installed.

It currently installs files in:

    /etc/udev/rules.d (make this one rtai-modules-common?)
    /usr/realtime-$VERSION


== update-deb-archive doesn't need ARCH

The makefile stamps do