Vnx-rootfs-uml-kernel

How to create a User-Mode-Linux Kernel for VNX

This document describes how to create a 32 bits UML kernel to be used with VNX. The procedure has been mainly tested for version 3.3.8, although it should work sith minor changes with previous 3.X versions (it does not with 3.4 version).

This procedure has been tested over a system with Ubuntu 10.04.4 32 bits. Although the procedure should work over a 64 bits system (installing gcc-multilib and using the SUBARCH variable should do the work), we had some problems trying to compile the 32 bits kernel over a 64 bits system (mainly when linking some libraries, for example, VDE ones).

• Download and uncompress kernel sources:

wget http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.3.8.tar.gz
tar xfvz linux-3.3.8.tar.gz
cd linux-3.3.8

• Download mconsole exec kernel patch:

wget vnx.dit.upm.es/vnx/kernels/mconsole-exec-3.3.8.patch

• Apply mconsole-exec patch:

patch -p1 < mconsole-exec-3.3.8.patch

• Configure kernel options (do not forget to enable support in kernel for ISO9660 and EXT4 file system format support):

make defconfig ARCH=um SUBARCH=i386
make menuconfig ARCH=um SUBARCH=i386

• Compile the kernel

make ARCH=um SUBARCH=i386
strip linux

• Check the kernel having a look at the version and options:

./linux --version
./linux --showconfig

• Or, better, starting a virtual machine with that kernel:

./linux ubda=rootfs mem=128M

Note: change 'rootfs' by the root filesystem filename you will use to test the kernel.

• Optionally, if you want to create a tar file with the kernel, modules and config file for distribution:

mkdir linux-um-3.3.8-src
cp linux linux-um-3.3.8-src/linux-um-3.3.8
mkdir linux-um-3.3.8-src/modules
make modules_install INSTALL_MOD_PATH=linux-um-3.3.8-src/modules/ ARCH=um SUBARCH=i386
cd linux-um-3.3.8-src/modules/lib/modules/
tar cfv modules-3.3.8.tar 3.3.8
mv modules-3.3.8.tar ../../../
cd ../../../
rm -rf modules
vi README-linux-um-3.3.8
cp ../.config config-linux-um-3.3.8
cd ..
tar cfvz linux-um-3.3.8.tgz linux-um-3.3.8-src