View source for User:Alex Ivanov/Building the Kernel

= How To Build a Kernel =
Here are details developers care about in order to '''modify, build, test''' parisc-linux kernels. Note that just because a kernel option can be select, does NOT mean it works. Trial and error is usually the only sure way to find out. Reports of such adventures are always welcome on the parisc-linux [mailto:linux-parisc@vger.kernel.org mailing list].
<ol>
<li>'''Install minimal set of tools'''
<pre>
aptitude install libncurses-dev bc
</pre></li>
<li>'''Obtain kernel source and build tools''': Stable kernel sources are available via <tt>aptitude install linux-source-XX</tt> (where XX is something like "2.4.25-32" or "2.6.6-32"). You may also download a tarball from the [https://www.kernel.org/ The Linux Kernel Archives] or <tt>git clone</tt> from [http://git.kernel.org/cgit/linux/kernel/git Kernel.org git repositories]. The most interested repos should be: [http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/] and [http://git.kernel.org/cgit/linux/kernel/git/deller/parisc-linux.git/]. You may start with first, but if you need some recent PA-RISC changes hadn't yet been imported to the mainline, pick a second one (usually you would be interested in some particular branch). Note that <tt>aptitude install linux-source-<any_recent></tt> '''step is a must''' (even if you decided to pick the sources from another place) as it will install most of required build tools. You may then opt-out <tt>linux-source-XX</tt> by issuing <tt>aptitude remove</tt>, if you don't need these sources.
<pre>
cd /usr/src
# verify ~350MB free
df -h .
</pre>
* Tarball
<pre>
wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.11.tar.xz
tar -xJf linux-3.11.tar.xz
</pre>
* Git
<pre>
git clone git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux.git
git checkout <branch/tag/commit>
</pre></li>
<li>'''Choosing toolchain version''': The good practice is to leave the one being installed during [[#Obtain kernel source and build tools]] phase. But if you can't sucessfully build the kernel using current toolchain version or you have other reasons, you may set a more fresh one.
<pre>
optionally: aptitude remove gcc-XX
aptitude install gcc-YY
</pre>
As for installing of another <tt>binutils</tt> version, it's usually easier to use <tt>aptitude</tt> frontend for this purpose.
''Important:'' See how to make installed toolchain versions default ones: http://stackoverflow.com/a/9103299</li>
<li>'''For 64-bit kernels: Install missing build tools'''
<pre>
aptitude install binutils-hppa64 gcc-XX-hppa64
</pre>
Where <tt>XX</tt> usually choosen to be same version as it's 32-bit counterpart.
</li>
<li>'''Configure Kernel Options'''
<pre>
cd /usr/src/linux-2.6
# clone the nearest _config to start with
cp arch/parisc/configs/b180_config .config
# You can also "make config" or "make menuconfig" here
# to adjust the .config if kernel defaults don't suit you.
make oldconfig # ARCH=parisc when cross-compiling
</pre></li>
On Debian with systemd you need to use Debian stock config as basis
<pre>
cd /usrc/src
xz -d linux-config-XX/config.hppa_none-flavor.xz
cp config.hppa_none-flavor linux-source-XX/.config
</pre>
<li>'''Build Kernel Executables'''
<pre>
make -j<N> # ARCH=parisc CROSS_COMPILE=...
# must be root user
make modules_install
</pre>
<tt>N</tt> is number of parallel processes there. You may add <tt>V=1</tt> to get verbose output of build process.</li>
<li>'''Installing the kernel'''
The resulting kernel image is <tt>/usr/src/linux-2.6/vmlinux</tt>. Normally, x86-linux will save the existing vmlinux and install the new kernel with <tt>make install</tt>. The "dpkg -i" steps above do about the same thing. Here is one way to do it manually:
<pre>
cd /boot
mv vmlinux vmlinux.old
mv System.map System.map.old
cd /usr/src/linux-2.6
cp System.map vmlinux /boot/
sync
reboot
</pre>
''NOTE: One does not need to run palo when replacing an existing kernel.''

Another way is to rename <tt>vmlinux</tt> with revision info, reboot, interrupt autoboot and specify interactive boot, specify the new kernel via palo, and finally once the new kernel is booted, modify <tt>/etc/palo.conf</tt> to match (and run <tt>palo</tt> again). Start with something like:
<pre>
cp vmlinux /boot/vmlinux-2.6.6-pa1
cp System.map /boot/System.map-2.6.6-pa1
cp .config /boot/config-2.6.6-pa1
sync
reboot
...
</pre></li>
</ol>