[QEMU][Raspberry Pi] Building With QEMU User Mode Emulation

In user mode, only the ARM CPU is emulated and your real file system is used as storage.
1.
mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc
cat /proc/sys/fs/binfmt_misc/status
If it says enabled, you’re good to go.


2. create a directory to hold your chroot environment:
export LFS=/lfs
mkdir $LFS
cd $LFS
wget http://circu.it/pilfs/ch5-tools-20141203.tar.xz
tar xvf ch5-tools-20141203.tar.xz


3. Install qemu to get qemu-arm binary
apt-get install qemu binfmt-support qemu-user-static


Copy qemu-arm-static to Emulation system.

mkdir -pv $LFS/usr/bin
cp -v /usr/bin/qemu-arm-static $LFS/usr/bin

4. Make a wrapper binary that will call qemu-arm-static with the correct arguments to emulate the same CPU family and kernel version as that of a Raspberry Pi.

wget http://www.intestinate.com/pilfs/patches/qemu-arm-wrapper.c
gcc -static qemu-arm-wrapper.c -s -o qemu-arm-wrapper
cp -v qemu-arm-wrapper $LFS/usr/bin

5. Register a binfmt_misc handler for our ARM binaries

echo ":arm: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-wrapper:" > /proc/sys/fs/binfmt_misc/register

6. trying to chroot into your /lfs directory:

chroot "$LFS" /tools/bin/env -i HOME=/root TERM="$TERM" PS1='\u:\w\$ ' PATH=/bin:/usr/bin:/sbin:/usr/sbin:/tools/bin /tools/bin/bash --login +h

7. See a prompt that reads “I have no name!”, everything is working correctly.

Reference:

1. QEMU User Emulation
2. Linux From Scratch on the Raspberry Pi