ARM/N900/Install/chroot

Revision as of 18:50, 29 May 2010

Under construction

NOTE: This instruction covers the case where user wants to chroot to a MeeGo image with the Nokia N900 device where Maemo 5 is installed.

One issue with a chroot installation is finding space for it. The SD card and Mydocs have plenty of space but they use FAT32 as a file system, so they can't be used directly. A solution is to mount loopback images. The easiest way to get started is to use a prebuilt loopback image.

If a prebuilt loopback image is not yet available, you can create it from a tarball.

Creating a loopback image from a tarball

Create 2GB image file

dd if=/dev/zero of=/home/user/MyDocs/meego-image bs=1024 count=2097152

Create filesystem on image file

mkfs.ext3 /home/user/MyDocs/meego-image

Create mount point and loopback mount the image

export MEEGO_ROOT="/mnt/meego_root"
mkdir $MEEGO_ROOT
mount -o loop /home/user/MyDocs/meego-image $MEEGO_ROOT

Install GNU tar (Busybox tar and GNU tar have some unfortunate compability problems) from Maemo Extras repository.

apt-get install tar-gnu

Check if the Meego rootfs image has an extra /SOMEDIR at a beginning of the actual system files.

gtar -tzf <meego-image>

Unpack the Meego image

# If there was an extra /SOMEDIR at the beginning strip it away when unpacking
gtar --strip-components 1 -xzf <meego-image> -C $MEEGO_ROOT

# otherwise just extract the image
gtar -xzf <meego-image> -C $MEEGO_ROOT

Umount the image

umount $MEEGO_ROOT

You now have a loopback image ready to be chrooted into

Chrooting into a loopback image

Using a script to chroot into an image makes the process faster and safer.

Copy the code below to a meego_chroot.sh script and remember to chmod +x it.

Usage: ./meego_chroot.sh <path_to_meego-arm-n900-loop.img>

Image downloaded from http://repo.meego.com/MeeGo/releases/1.0/core/images/meego-n900-open-armv7l/ contains entire hard drive, not single partition. Partition starts at byte 16384, so line mounting image

 mount -o loop ${MEEGO_IMAGE} ${MEEGO_ROOT}

should be replaced by

 losetup /dev/loop0 ${MEEGO_IMAGE} -o 16834
 mount /dev/loop0 ${MEEGO_ROOT}

You may always execute the commands below manually if you like. Changing the prompt is optional and you only need to do it once per image.

 #!/bin/sh
 
 GRAPHICS_LIBS="\
 /usr/lib/libIMGegl.so \
 /usr/lib/libglslcompiler.so \
 /usr/lib/libpvrPVR2D_DRI2WSEGL.so \
 /usr/lib/libsrv_um.so \
 /usr/lib/libOpenVGU.so \
 /usr/lib/libpvrPVR2D_BLITWSEGL.so \
 /usr/lib/libpvrPVR2D_FRONTWSEGL.so \
 /usr/lib/libpvrPVR2D_FLIPWSEGL.so \
 /usr/lib/libpvrPVR2D_X11WSEGL.so \
 /usr/lib/libOpenVG.so \
 /usr/lib/libEGL.so \
 /usr/lib/libPVRScopeServices.so \
 /usr/lib/libpvr2d.so \
 /usr/lib/libGLESv2.so"
 
 ### Prepare and mount the image ###
 MEEGO_IMAGE=$1
 MEEGO_ROOT=/mnt/meego_root
 mkdir -p ${MEEGO_ROOT}
 mount -o loop ${MEEGO_IMAGE} ${MEEGO_ROOT}
 
 ### Mount system directories ###
 echo "Mounting system directories inside the chroot environment..."
 mount -o bind /proc ${MEEGO_ROOT}/proc
 mount -o bind /sys  ${MEEGO_ROOT}/sys
 mount -o bind /dev ${MEEGO_ROOT}/dev
 mount -o bind /dev/pts ${MEEGO_ROOT}/dev/pts/
 
 mount -o bind /var/lib/dbus/ ${MEEGO_ROOT}/var/lib/dbus/
 mount -o bind /usr/share/fonts ${MEEGO_ROOT}/usr/share/fonts
 
 mount -o bind /tmp  ${MEEGO_ROOT}/tmp
 mount -o bind /var/run  ${MEEGO_ROOT}/var/run
 mount -o bind /home ${MEEGO_ROOT}/home
 
 ### Setup ###
 rm -f ${MEEGO_ROOT}/etc/resolv.conf
 cp /etc/resolv.conf ${MEEGO_ROOT}/etc/resolv.conf
 
 rm -f ${MEEGO_ROOT}/etc/mtab
 ln -s /proc/mounts ${MEEGO_ROOT}/etc/mtab
 
 # Prepare .bashrc for setupping chroot environment
 grep -q -s MeeGo ${MEEGO_ROOT}/root/.bashrc
 if [ "$?" -ne "0" ]; then
   echo "# MeeGo" >> ${MEEGO_ROOT}/root/.bashrc
   echo "source /tmp/session_bus_address.user" >> ${MEEGO_ROOT}/root/.bashrc
   
   # Change the prompt - this is optional
   # echo "export PS1=MeeGo-chroot:\\\w\\\\\$" >> ${MEEGO_ROOT}/root/.bashrc
 fi
 
 # Setup .bashrc for cases when sudo is used
 grep -q -s MeeGo ${MEEGO_ROOT}/home/user/.bashrc
 if [ "$?" -ne "0" ]; then
   echo "# MeeGo" >> ${MEEGO_ROOT}/home/user/.bashrc
   echo "source /tmp/session_bus_address.user" >> ${MEEGO_ROOT}/home/user/.bashrc
   
   # Change the prompt - this is optional
   # echo "export PS1=MeeGo-chroot:\\\w\\\\\$" >> ${MEEGO_ROOT}/home/user/.bashrc
 fi
 
 # Copy graphics libraries from host  
 for lib in ${GRAPHICS_LIBS}; do
   cp ${lib} ${MEEGO_ROOT}/usr/lib/
 done
 
 # Copy pulseaudio files from host
 cp /usr/lib/libpulse* ${MEEGO_ROOT}/usr/lib/
 
 ### Start your engines ###
 echo -e "chrooting to ${MEEGO_ROOT}...\n"
 cd ${MEEGO_ROOT}
 chroot ${MEEGO_ROOT} /bin/bash
 
 ### Cleanup ###
 echo "Cleaning mounts..."                                                                                      
 cd ~
 umount ${MEEGO_ROOT}/dev/pts
 umount ${MEEGO_ROOT}/dev
 umount ${MEEGO_ROOT}/sys
 umount ${MEEGO_ROOT}/proc
 
 umount ${MEEGO_ROOT}/var/lib/dbus/
 umount ${MEEGO_ROOT}/usr/share/fonts
 
 umount ${MEEGO_ROOT}/tmp
 umount ${MEEGO_ROOT}/var/run
 umount ${MEEGO_ROOT}/home
 
 umount ${MEEGO_ROOT}
 echo

Problems

If script fails for what ever reason it is likely that cleanup is needed afterwards.

# Check if any programs inside chroot are still running
ps

# Check if anything is still mounted inside chroot
mount

# Umount all the mounts inside chroot and remember the order
# first 'umount /dev/pts' and only after that 'umount /dev'

# Check used loop device
losetup

# Free the loop device, replace X with correct number
losetup -d /dev/loopX