BUILDING LVM2 FOR USE ON ANDROID

The LVM source was written for standard glibc-based GNU/Linux systems,
and doesn't build agains Android libc.  We could invest time and effort
into porting it to Android, but it's easier to just statically link the
LVM binary against glibc (we already have to use a statically linked
binary, since the boot image doesn't ship shared libraries).

To build LVM with glibc, you will need either an actual GNU/Linux ARM
system with a development environment (gcc, make, and glibc header
files) set up, or a GNU/Linux ARM cross-compiler environment.

For native compilation, any recent Linux distribution and any ARM device
should do.  If you don't have something like a BeagleBoard or
SheevaPlug, you can install a GNU/Linux chroot on any rooted Android
device.  You'll need the development tools for your chosen distribution
(install metapackage "build-essential" on Debian or Ubuntu, or package
group "Development Tools" on Fedora-derived distros).

For cross compilation, you'll need a Linux box, a cross-compiler
toolchain for GNU/Linux ARM EABI, and (for now) the qemu-arm user mode
emulator (to keep the configure script from getting confused).  The
Linaro prebuilt GCC toolchain and the CodeSourcery CodeBench Lite
toolchain for ARM Linux should work; the Android NDK toolchain will not.
(Debian users can install the Emdebian cross toolchain from
http://www.emdebian.org/crosstools.html).

The binaries in lvm-bin/ were compiled with an Emdebian squeeze/armel
cross compilation toolchain running on a Debian squeeze/amd64 machine.

Once you have your development environment set up, do the following to
compile LVM:

1. Grab the LVM source.  If it's not already in this tree, you can fetch
it via git ($ is your prompt):

    $ git submodule init
    $ git submodule update

2. Configure the LVM source:

    $ cd lvm-src/
    $ ./configure --prefix=/lvm --enable-static_link --disable-readline \
      --disable-selinux --with-pool=none --with-cluster=none \
      --with-confdir=/lvm/etc --with-default-run-dir=/data/lvm/run \
      --with-default-system-dir=/lvm/etc \
      --with-default-locking-dir=/data/lvm/lock \
      --with-optimisation="-Os -march=armv5te -mtune=cortex-a8 -mthumb"

(Explanation: --prefix, --with-confdir, --with-default-run-dir,
--with-default-system-dir, --with-default-locking-dir tell LVM where to
find its pieces.  --enable-static_link enables the building of a
statically linked binary.  --disable-readline --disable-selinux
--with-pool=none --with-cluster=none disable features we don't need.
--with-optimisation changes the compiler flags to produce a smaller binary
while still complying with Android's "armeabi" ABI.)

To cross-compile, you first need to set up your system so that ARM
binaries will automatically be emulated using qemu-arm.  Your
distribution may already have set this up for you (e.g. on Debian with
the qemu-user-static and binfmt-support packages); if not, make sure
your kernel has CONFIG_BINFMT_MISC enabled, and then do

    # mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
    # echo ":arm-qemu:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-arm:" > /proc/sys/fs/binfmt_misc/register

as root.  Then, when running configure, do

    $ export CC=arm-linux-gnueabi-gcc	# replace with your cross compiler
    $ ./configure --host=arm-linux-gnueabi \
      --prefix=/lvm --enable-static_link --disable-readline \
      --disable-selinux --with-pool=none --with-cluster=none \
      --with-confdir=/lvm/etc --with-default-run-dir=/data/lvm/run \
      --with-default-system-dir=/lvm/etc \
      --with-default-locking-dir=/data/lvm/lock \
      --with-optimisation="-Os -march=armv5te -mtune=cortex-a8 -mthumb"

3. Build the software:

    $ make

The resulting statically linked unstripped LVM binary will be located in
tools/lvm.static in the LVM source tree, and an example configuration
file is located in doc/example.conf.