Add Packages To Ubuntu Preinstalled Images

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Ubuntu delivers pre-installed images for OMAP3 and OMAP4, in particular on http://cdimage.ubuntu.com/ubuntu-netbook/ports/releases/.

These images are much faster to install (10 to 20 minutes) than standard "live" images (up to several hours). That's why these images for shipped by default. See this page and this page for details.

Here are instructions to add your own packages to the pre-installed images. They assume that sufficient space is available. At the moment, the pre-installed root partition has 200-300 MB of free space.

Contents

Requirements

You need to run the below manipulations on an armv7 board (like OMAP3 and OMAP4 ones) running a GNU/Linux distribution. That's because we are going to chroot to an armv7 rootfs.

Making the pre-installed rootfs bigger

This can be needed if you have a significant number of packages to add. Currently, Ubuntu's pre-installed images just have between 200 and 300 MB of free space.

Here is a script that you can use to make the rootfs part of these images bigger.

#!/bin/sh
# Grows a disk image by the specified number of megabytes
#
# Assumptions: an image with 2 partitions, the 2nd one
# in ext3 format.
#
# Example: grow-disk-image infile.img outfile.img 512

INPUT=$1
OUTPUT=$2
TMP=${OUTPUT}.tmp
SIZE=$3

DD=/bin/dd
CAT=/bin/cat
RM=/bin/rm
SUDO=/usr/bin/sudo
LOSETUP=/sbin/losetup
RESIZE2FS=/sbin/resize2fs
FSCKEXT3=/sbin/fsck.ext3
FDISK=/sbin/fdisk
TAIL=/usr/bin/tail
AWK=/usr/bin/awk

# Copying the initial image + SIZE zeros at the end
echo "Copying $INPUT to $OUTPUT and adding zeros at the end..."
$DD if=/dev/zero of=$TMP bs=1M count=$SIZE
$CAT $INPUT $TMP > $OUTPUT
$RM -f $TMP

# Modify the partition table - Delete the 2nd partition
# and create it again with all available space
echo "Going to need your password to run a few commands with sudo..."

# Before this, find the first available loop device
LOOP=`$SUDO $LOSETUP -f`
$SUDO $LOSETUP $LOOP $OUTPUT
$CAT <<END |$SUDO $FDISK $LOOP
d
2
n
p
2


w
END

# Free the loop device
$SUDO $LOSETUP -d $LOOP

# Now, access the second partition on the card
# First, compute the offset corresponding to the 2nd partition
start=`$FDISK -lu $OUTPUT | $TAIL -1 | $AWK '{print $2}'`

# Running this again. Another loop device can have been used in the meantime
LOOP=`$SUDO $LOSETUP -f`

$SUDO $LOSETUP -o $(($start * 512)) $LOOP $OUTPUT

# Resize at last!
$SUDO $RESIZE2FS $LOOP

# Just to be sure, fsck the partition
$SUDO $FSCKEXT3 -f $LOOP

# Cleanup
$SUDO $LOSETUP -d $LOOP
echo "Resizing complete" 

Mounting the pre-installed rootfs

Run fdisk -lu maverick-preinstalled-netbook-armel+omap4.img and read the starting block for the rootfs partition:

You must set cylinders.
You can do this from the extra functions menu.
Disk maverick-preinstalled-netbook-armel+omap4.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

                                       Device Boot      Start         End      Blocks   Id  System
maverick-preinstalled-netbook-armel+omap4.img1   *          63      144584       72261    c  W95 FAT32 (LBA)
maverick-preinstalled-netbook-armel+omap4.img2          144585     4401809     2128612+  83  Linux

Now, mount this partition:

mkdir -p /mnt/rootfs
mount -o loop,offset=$((144585*512)) ubuntu.img /mnt/rootfs

Modifying the pre-installed partition

Before running chroot, replicate the basic filesystems that Ubuntu mounts:

for f in /proc /sys /dev /dev/pts /dev/shm /var/run /var/lock
do
  sudo mount -o bind $f /mnt/rootfs/$f
done

Without the above, some commands may not work properly, being unable to find data in /proc and /sys in particular.

If you are behind a proxy, copy your files defining your proxy settings (typically /etc/environment) under the same path /mnt/rootfs.

Also copy your name resolution settings to the rootfs:

sudo cp /etc/resolv.conf /mnt/rootfs/etc/resolv.conf

Modify the rootfs

sudo chroot /mnt/rootfs/

If you are using a special package source, you can add it to /etc/apt/sources.list

Now, update your package list and install extra packages. For example:

apt-get update
apt-get install openssh-server

Once you are done, exit the chroot:

exit

Closing

sudo rm /mnt/rootfs/etc/resolv.conf

You may also undo your proxy setting changes (typically /etc/environment).

Then, unmount the filesystems replicated in the chroot:

for f in /var/lock /var/run /dev/shm /dev/pts /dev /sys /proc
do
  sudo umount /mnt/rootfs/$f
done

You are done!

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