In the Debian example, the wiki introduced NetInstall. Later I find out the mk_mmc.sh script shown there to be useful for (1) duplicating and (2) restoring working Linux backup to new or corrupted MMC/SD card. I break down that Robert C. Nelson’s mk_mmc.sh script at GitHub to small routines for setting up the card.

Typical boot-rootfs partitions of SD card to boot ARM-Linux boards

It’s an elegant script automating the process of preparing SD card for embedded Linux, but requires large downloading on the run (mostly root file system and then U-Boot binaries and loader config). Duplicating/restoring means we already have those and probably only need to do elementary process rather than full card preparation. Below are some processes that can be repeatedly used.

Checking Tool Versions

The tools to work with are common in Linux distribution (I used Ubuntu) and require root privilege. The script checked for fdisk and parted installed. My versions are

$ fdisk -v
fdisk (util-linux-ng 2.17.2)
$ parted -v
parted (GNU parted) 2.2

Originally mk_mmc.sh will exit If “GNU Fdisk” found instead. Also for the above parted version, “--align cylinder” argument will be used.

Creating Two Partitions

Setting up two partitions which are the boot image (FAT 16) and root file system (ext4). The SD card plugged in through USB card reader found as /dev/sdb in this example (we’re formatting be sure of this!). If you plug MMC card to laptop slot, it may be found as /dev/mmcblk0.

1. Format card into a single disk

$ parted --script /dev/sdb mklabel msdos
$ fdisk -l /dev/sdb

2. Create the boot partition (allocating 64MB)

$ fdisk /dev/sdb << END
n
p
1
1
+64M
t
e
p
w
END

then make sure it’s done.

$ sync

3. Flag it as boot

$ parted --script /dev/sdb set 1 boot on

4. Create the root file system by first determining space left after the first partition

$ END_BOOT=$(LC_ALL=C parted -s /dev/sdb unit mb print free | grep primary | awk '{print $3}' | cut -d "M" -f1)
$ echo $END_BOOT 
69.7
$ END_DEVICE=$(LC_ALL=C parted -s /dev/sdb unit mb print free | grep Free | tail -n 1 | awk '{print $2}' | cut -d "M" -f1)
$ echo $END_DEVICE 
3951

In this case 4GB SD card is used and the above calculation will stretch space left from 69.7 to 3951 of as rootfs partition.

$ parted --script --align cylinder /dev/sdb mkpart primary ext4 $END_BOOT $END_DEVICE

5. Format boot and rootfs according to each file system type with those naming also. They’re already accessible as /dev/sdb1 and /dev/sdb2 (previously didn’t exist) or relevant /dev/mmcblk0p(some index).

$ mkfs.vfat -F 16 /dev/sdb1 -n boot
$ mkfs.ext4 /dev/sdb2 -L rootfs

6. Finally we have something like the output of parted below

$ LC_ALL=C parted -s /dev/sdb unit mb print free 
Model: HUAWEI MMC Storage (scsi)
Disk /dev/sdb: 4023MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
 
Number  Start   End     Size    Type     File system  Flags
 1      0.03MB  70.9MB  70.8MB  primary  fat16        boot, lba
        70.9MB  4023MB  3953MB           Free Space

(yes I used Huawei modem as the microSD card reader)

Restoring Linux

For the boot partition content we can simply copy-paste the backup files, while for rootfs normally compressed file (preserving path information) is used for backup. Restore this by mounting rootfs and then unpacking the file (again /dev/sdb2 in this case).

[root@host]$ mkdir /media/rootfs
[root@host]$ mount -t ext4 /dev/sdb2 /media/rootfs
[root@host]$ pv armel-rootfs-201110131018.tar | sudo tar --numeric-owner --preserve-permissions -xf - -C /media/rootfs

Below is an example of how to backup rootfs from the mounted SD card (/media/rootfs).

[root@host]$ cd /media/rootfs
[root@host]$ /media/rootfs# tar --numeric-owner --preserve-permissions -cvf /home/arif/Documents/arm-linux/ubuntu/rootstock-rootfs/armel-rootfs-201202141421.tar ./*

(Check my other post related to creating rootfs)

Creating Swap

mk_mmc.sh also offers optional swap creation. It is a “file” inside rootfs partition created by

[root@host]$ dd if=/dev/zero of=/media/rootfs/SWAP.swap bs=1M count=250
[root@host]$ mkswap /media/rootfs/SWAP.swap

(the above will create 262MB swap inside rootfs SD card currently mounted to /media/rootfs of the laptop)

It will be mounted as swap by the ARM-Linux board via fstab setting configured below.

[root@host]$ echo "/SWAP.swap  none  swap  sw  0 0" >> /media/rootfs/etc/fstab

Synchronize and safely remove the card

[root@host]$ sync
[root@host]$ umount /media/rootfs

I bricked one of these DevKit8500D by overvoltaged it to 12V DC. Yes, It has no regulator.

Various howto made net-boot or preinstalled images seem feasible, but trying them is another thing. The first attempt was to boot Ubuntu Lucid 10.04 LTS to have similar distribution as my laptop, but it would stop at boot with the message

Error: unrecognized/unsupported machine ID (r1 = 0x00000ae9).

The above ID (2793 in decimal) isn’t found in Lucid released with linux 2.6.32-21. Ubuntu Natty 11.04 boot image didn’t complain because the ID already listed in /usr/src/linux-source-2.6.38/arch/arm/tools/mach-types

...
 nemini                  MACH_NEMINI             NEMINI                  2793
...

However, ubuntu-11.04-preinstalled-headless-armel+omap.img.gz wouldn’t finish loading the linux kernel 2.6.38 somehow. Hence, I replaced the root file system using rootfs created using RootStock method. After successful boot, I installed linux-image-2.6.38-8-omap_2.6.38-8.42_armel.deb to have the rootfs kernel lib files updated (this would require wireless-crda dependency to be installed).

Creating Lucid RootStock & Replacing Natty’s

Using RootStock relies much on the host environment, in my case (version 0.1.99.3) the laptop has Lucid with 2.6.38 kernel (Natty), and it failed to create rootfs with option --dist natty by stopping at this QEMU error:

qemu: fatal: cp15 insn ee1d6f70
 
R00=4009f960 R01=420822e8 R02=0d696914 R03=000086a8
R04=00008ef0 R05=00000000 R06=000097c9 R07=42082308
R08=00020040 R09=00000000 R10=4009f000 R11=00000000
R12=00008b88 R13=4007f7f8 R14=4008f450 R15=4008aea0
PSR=20000030 --C- T usr32

DevKit8500D also freezed on boot when too many seeds used in the rootfs. A minimal seeds of Lucid rootfs used is

[ubuntu-laptop]$ sudo rootstock --fqdn omap --login ubuntu --password temppwd --imagesize 2G --seed wget,nano,linux-firmware,wireless-tools,usbutils --dist lucid --serial ttyO2 --components "main universe multiverse"

It will retrieve many packages from http://ports.ubuntu.com which takes long and produces i.e. armel-rootfs-201110261541.tgz.

A card at /dev/sdb with Natty boot images are obtained by

gunzip -c ubuntu-11.10-preinstalled-server-armel+omap.img.gz | sudo dd bs=4M of=/dev/sdb

The root file system will reside at /dev/sdb2 while boot images are in /dev/sdb1. To replace this with Lucid rootfs, run following steps

1
2
3
4
5
6

dd if=/dev/zero of=lucid-arm.img bs=1MB count=0 seek=1024
sudo mkfs.ext3 -F lucid-arm.img
sudo mount -o loop lucid-arm.img /mnt
sudo tar -C /mnt -zxf armel-rootfs-<some rootstock generated date>.tgz
sudo umount /mnt
sudo dd if=lucid-arm.img of=/dev/sdb2 bs=1MB count=0 seek=1024

There are reasons for why-not-using the included Ångström Linux (forked to linux-2.6.32-devkit8500) but this method of booting Ubuntu wasn’t straightforward after all. The on-board LAN (using Davicom DM9000AEP chip) doesn’t work and I need to use USB ethernet detected as Davicom DM9601 (a bit ridiculous?). Easycap USB video capture also works with this kernel as it has been part of 2.6.38 drivers/staging compilation.

DM9601 USB LAN

Before coming up with this combo, I’ve tried:

1. Ubuntu Lucid 10.04 CD Image: ubuntu-10.04-server-armel+omap.img
2. Ubuntu Oneiric 11.10 CD Image: ubuntu-11.10-preinstalled-server-armel+omap.img.gz
3. Robert C. Nelson’ Oneiric: ubuntu-11.10-r0-minimal-armel.tar.xz (as pointed out by the above eLinux page which has changed quite regularly since October 2011)

But nothing seemed to work.