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<h1>Installing Debian GNU/Linux in a chroot on a Samsung Galaxy S II</h1>
-<p><em>(Last updated 2011-11-25)</em></p>
+<p><em>(Last updated 2011-11-26)</em></p>
<p>
There are numerous how-tos on the web for installing a Debian chroot onto
a smartphone running Android, but most of them either give you an image
to install on your phone (which doesn't teach you anything) or have you
set up the Debian system on your desktop and copy it to the phone.
-Neither of these options appeal to me, so I've done it my own way and
+Neither of these options appeals to me, so I've done it my own way and
written this document to light the way for others, too.
</p>
<li>
You have an Android smartphone with access to a root shell via SSH. I run
<a href="http://www.cyanogenmod.com/">CyanogenMod 7.1</a> on my Galaxy S
-II, but any Android system with root SSH access will do.
+II, but any Android system with root SSH access will do, provided it has
+the following utilities:
+ <ul>
+ <li><tt>cat</tt></li>
+ <li><tt>chroot</tt></li>
+ <li><tt>dd</tt></li>
+ <li><tt>ln</tt></li>
+ <li><tt>mkdir</tt></li>
+ <li><tt>mke2fs</tt></li>
+ <li><tt>mount</tt></li>
+ <li><tt>tar</tt></li>
+ <li><tt>wget</tt> (used by <tt>cdebootstrap</tt>)</li>
+ </ul>
+If you don't have these utilities available to you, you will either need
+to find a way of installing them, or else find alternative ways of
+performing some of the steps in this how-to. Doing either is outside the
+scope of this how-to, but most of these utilities are provided by
+<tt>busybox</tt> on my device, so installing <tt>busybox</tt> should get
+you most of the way there.
+</li>
+<li>
+You have a reasonably fast and high-capacity Internet connection
+available on your Android phone. I will not be held responsible for any
+excess usage charges you incur on your mobile Internet package while
+downloading Debian onto your phone. ;-)
</li>
<li>
You have a basic understanding of Debian and its packaging system. This
</ul>
<p>
-If not all of these assumptions are true, please don't contact me if
-something doesn't go right for you when following this how-to.
+If not all of these assumptions are true, please don't contact me just to
+complain if something doesn't go right for you when following this
+how-to. Of course, alternative suggestions are welcome!
</p>
<h2>Preparation</h2>
<ul>
<li>
Download the <a href="http://packages.debian.org/sid/cdebootstrap-static">cdebootstrap-static</a>
-package for your architecture. Both armel and armhf packages should work
-on recent Android phones; if you have an older phone, you may need to
-stick with armel. I'll be using armhf in this tutorial, but you are free
-to choose whichever architecture suits you best.
+package for your architecture. Both <tt>armel</tt> and <tt>armhf</tt>
+packages should work on recent Android phones; if you have an older
+phone, you may need to stick with <tt>armel</tt>. I'll be using
+<tt>armhf</tt> in this tutorial, but you are free to choose whichever
+architecture suits you best.
</li>
<li>
Now, copy the files needed for <tt>cdebootstrap</tt> to work across to
<code>
$ mkdir /tmp/cdebootstrap && cd /tmp/cdebootstrap<br>
$ ar x /path/to/cdebootstrap-static_0.5.8+b1_armhf.deb data.tar.gz<br>
-$ tar xzOf data.tar.gz ./usr/lib/cdebootstrap/cdebootstrap_0.5.8+b1_armhf.tar.gz | ssh root@$PHONE 'tar xz -C /data/local/bin/'
+$ tar xzOf data.tar.gz ./usr/lib/cdebootstrap/cdebootstrap_0.5.8+b1_armhf.tar.gz | ssh root@$PHONE 'tar xzC /data/local/bin/'
+</code>
+Remember to replace <tt>$PHONE</tt> with the hostname of your phone.
+</li>
+<li>
+Unfortunately, the version of <tt>cdebootstrap</tt> included in the
+tarball appears to segfault on Android systems. I don't know why this
+happens, but replacing it with the binary provided in the package seems
+to fix this issue:
+<code>
+$ tar xzOf data.tar.gz ./usr/bin/cdebootstrap-static | ssh root@$PHONE 'cat >/data/local/bin/cdebootstrap'
</code>
-Obviously, replace <tt>$PHONE</tt> with the hostname of your phone.
</li>
</ul>
larger than 2 GiB, the FAT file system it lives on will complain and you
will lose the image next time you reboot. This happened to me the first
time I tried it, and I hadn't made a backup, so I had to do it all over
-again. :(
+again. :-(
</p>
<p>
# mke2fs -Fj /mnt/sdcard/debian.img<br>
# mkdir /debian<br>
# mount -t ext3 -o noatime,errors=remount-ro /mnt/sdcard/debian.img /debian
+# for fs in /dev /proc /sys; do mount -o bind "$fs" "/debian$fs"; done
</code>
<p>
+One last thing you need to do before setting up Debian:
+<tt>cdebootstrap</tt> expects the system shell to be at <tt>/bin/sh</tt>
+and fails without telling you why if it isn't. Since Android's system
+shell is <tt>/system/bin/sh</tt>, you have to appease
+<tt>cdebootstrap</tt> like so:
+</p>
+<code>
+# mkdir /bin && ln -s /system/bin/sh /bin/sh
+</code>
+
+<p>
+Now comes the fun bit, where we actually set up a Debian system. Still on
+your phone, run <tt>cdebootstrap</tt> to set up a file system tree in
+<tt>/debian</tt>. You may want to tweak the options below; I'm using
+<tt>ftp.debian-ports.org</tt> as my mirror because (at the time of
+writing) the <tt>armhf</tt> architecture is not yet fully integrated into
+the official archive. If you're using <tt>armel</tt>, or if you happen to
+live in the future, you can use your normal Debian mirror for this.
+Don't forget to replace <tt>unstable</tt> with whichever
+<a href="http://www.debian.org/releases/">suite</a> you want to install,
+but be aware that (at the time of writing) <tt>armhf</tt> only exists in
+<tt>unstable</tt> -- if you want <tt>stable</tt> or <tt>testing</tt>, and
+you downloaded an <tt>armhf</tt> <tt>cdebootstrap</tt> binary, you will
+need to specify the <tt>-aarmel</tt> option to <tt>cdebootstrap</tt>.
+</p>
+
+<code>
+# cdebootstrap --allow-unauthenticated -c/data/local/bin/cdebootstrap-support/ unstable /debian http://ftp.debian-ports.org/debian/
+</code>
+
+<p>
+We have to use <tt>--allow-unauthenticated</tt> because <tt>gpgv</tt>
+isn't available to authenticate signatures on Android. This command can
+take a while to complete, so go and have a coffee or something while you
+wait for Debian to download and install.
+</p>
+
+<h2>Fixing broken packages</h2>
+
+<p>
+It was the case for me that some packages failed to install from
+<tt>cdebootstrap</tt>. Fortunately, it had at least progressed to the
+point where a shell and <tt>dpkg</tt> were installed and usable in the
+chroot, so now we can leave <tt>cdebootstrap</tt> behind and work in
+Debian:
+</p>
+
+<code>
+# chroot /debian /bin/bash<br>
+# cd /var/cache/bootstrap<br>
+# dpkg -i *.deb
+</code>
+
+<p>
+At this point, <tt>dpkg</tt> may run into some problems. As the package
+archive changes over time and different people install different suites,
+your problems will very likely not be the same as mine, so here's where
+your familiarity with the Debian package tools comes in. ;-)
+</p>
+
+<p>
+The main issue I ran into here was circular dependencies. These can be
+fixed by the use of the <tt>--force-depends</tt> option to <tt>dpkg</tt>,
+to allow it to install and configure one of the packages in the
+dependency loop, so that you can then install the others normally. For
+example, I found that <tt>libc6</tt> depends on <tt>libgcc1</tt>, which
+pre-depends on <tt>multiarch-support</tt>, which depends on
+<tt>libc6</tt>. After running:
+</p>
+
+<code>
+# dpkg --force-depends --configure multiarch-support
+</code>
+
+<p>
+this circular dependency was no longer a problem, although there were
+other remaining circular dependencies that could be fixed in a similar
+way.
+</p>
+
+<p>
+Once you have resolved a few circular dependencies and want to try again,
+it is a good idea to run:
+</p>
+
+<code>
+# dpkg --configure -a
+</code>
+
+<p>
+before telling <tt>dpkg</tt> to try installing packages again, as the
+shell glob <tt>*.deb</tt> will simply present the packages in
+alphabetical order, which is usually not a sensible order in terms of
+satisyfing dependencies. <tt>dpkg --configure -a</tt> will make sure that
+packages which are already installed (and thus don't depend on any which
+aren't installed yet) get configured before those which aren't already
+installed (and might depend on installed packages being configured).
+</p>
+
+<h2>Installing a standard Debian package set</h2>
+
+<p>
+<tt>cdebootstrap</tt> will only install packages with a priority of
+<tt>required</tt> or <tt>important</tt>. While this will give you a
+powerful Unix-like base system, it doesn't include many utilities that
+you would get with a standard Debian system. Once all of your package
+dependency issues have been resolved, and everything in
+<tt>/var/cache/bootstrap/</tt> is installed, you can use
+<tt>aptitude</tt> to install a standard Debian system:
+</p>
+
+<code>
+# echo 'deb http://ftp.debian-ports.org/debian unstable main' >/etc/apt/sources.list<br>
+# echo 'nameserver 8.8.8.8' >/etc/resolv.conf<br>
+# aptitude update<br>
+# aptitude install debian-ports-archive-keyring<br>
+# aptitude install '~prequired|~pimportant|~pstandard'
+</code>
+
+<p>
+What you choose to install beyond this depends on your wants and needs,
+and how you like your Debian. ;-)
+</p>
+
+<h2>Initialising the Debian system at boot time</h2>
+
+<p>
+I have written a couple of simple scripts to ease getting Debian up and
+running. They come in pairs; one of them lives in Android and chroots to
+Debian, and the other lives in Debian and gets run after the chroot. You
+can find a copy of these scripts in
+<a href="http://git.steven-mcdonald.id.au/?p=android-debian.git;a=tree">Gitweb</a>,
+or clone the git repository with:
+</p>
+
+<code>
+$ git clone git://git.steven-mcdonald.id.au/android-debian.git
+</code>
+
+<p>
+For usage information, please refer to the <tt>README</tt> in that git
+repository.
</p>
</div>
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