How to create a bootable microSD card (XUELK)

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AXEL ULite-top.png Applies to AXEL ULite
SBC Lynx-top.png Applies to SBC Lynx


200px-Emblem-important.svg.png The procedure described here was tested with a physical machine. In case of a virtual machine such as the MVM, it might not work properly. Also, it is worth remembering that USB controller of the MVM is disabled by default. See also this section. 200px-Emblem-important.svg.png


This article shows how to create a bootable microSD card for the XUELK kit by using a simple bash script. The procedure has been tested on a Linux PC running Ubuntu 12 distribution with

  • a 16 GB microSD card [1]
  • the binary files delivered along with the XUELK 1.1.3.

The resulting card is partitioned as depicted here.

The script - named mksd.sh - looks like this:

#!/bin/bash

if [[ -z $1 || -z $2 || -z $3 || -z $4 ]]
then
	echo "$0 Usage:"
	echo "	$0 <device> <u-boot.imx> <binaries directory> <rootfs tar.bz2>"
	echo "	Example: $0 /dev/sdc u-boot.imx binaries/ rootfs.tar.bz2"
	exit
fi

if [ "$(whoami)" != "root" ]
then
	echo "you must be root to run this script!"
	exit
fi

if ! [[ -b $1 ]]
then
	echo "$1 is not a valid block device!"
	exit
fi

if ! [[ -e $2 ]]
then
	echo "Incorrect u-boot.imx location!"
	exit
fi

if ! [[ -d $3 ]]
then
	echo "Incorrect Binaries location!"
	exit
fi

if ! [[ -f $4 ]]
then
	echo "Incorrect rootfs location!"
	exit
fi

DRIVE=$1
if [[ "$DRIVE" == *"mmcblk"* ]]
then
	echo "You're using a mmc device, I need to fix partition names"
	PART="p"
else
	PART=""
fi
UBOOT=$2
BINARIES=$3
RFS=$4

echo "All data on "$DRIVE" now will be destroyed! Continue? [y/n]"
read ans
if ! [ $ans == 'y' ]
then
	exit
fi

echo "[Partitioning $1...]"

dd if=/dev/zero of=$DRIVE bs=1024 count=1024

SIZE=`fdisk -l $DRIVE | grep Disk | awk '{print $5}'`

echo DISK SIZE - $SIZE bytes

CYLINDERS=`echo $SIZE/255/63/512 | bc`

{
	echo 10,1380,0x0c,*
	echo 1390,,83,-
} | sfdisk -D -H 255 -S 63 -C $CYLINDERS $DRIVE
sudo partprobe

echo "[Making filesystems...]"
mkfs.vfat -F 32 -n BOOT "$DRIVE$PART"1 #> /dev/null
mkfs.ext3 -L ROOTFS "$DRIVE$PART"2 #> /dev/null

echo "[Copying files...]"

binaries_dir=${BINARIES%/}
mount "$DRIVE$PART"1 /mnt
cp -av --no-preserve=ownership $binaries_dir/* /mnt/
umount "$DRIVE$PART"1

echo "[Extracting rfs (this may take a while...)]"
mount "$DRIVE$PART"2 /mnt
tar jxf $RFS -C /mnt > /dev/null
chmod 755 /mnt
umount "$DRIVE$PART"2

echo "[Programming u-boot.imx]"
dd if=$UBOOT of=$DRIVE bs=1k seek=1

echo "[Done]"

Here is an example that shows how to use this script. Let's assume that the binary files were downloaded in the xuelk-1.1.3 subdirectory of the working directory. Before invoking the script, the following files has to be renamed in order to make them compatible with the default U-Boot environment variables:

  • bootscript: boot.scr
  • Linux kernel: uImage
  • Device tree blob: imx6ul-lynx.dtb.

This is the list of the binary files that will be used by the script:

sysadmin@stagesw:~/devel/sbclynx/uSD$ ll xuelk-1.1.3/
total 51436
drwxrwxr-x 2 sysadmin sysadmin     4096 Mar 15 14:12 ./
drwxrwxr-x 3 sysadmin sysadmin     4096 Mar 14 18:03 ../
-rw-rw-r-- 1 sysadmin sysadmin      668 Mar 14 14:11 boot.scr
-rw-rw-r-- 1 sysadmin sysadmin    31436 Mar 12 20:53 imx6ul-lynx.dtb
-rw-rw-r-- 1 sysadmin sysadmin  6765480 Mar 12 20:54 uImage
-rw-rw-r-- 1 sysadmin sysadmin   507948 Mar 12 21:03 xuelk-1.1.2_mx6ul_lynx_u-boot.imx
-rw-rw-r-- 1 sysadmin sysadmin 45346549 Mar 15 12:19 xuelk-1.1.3_lynx-image-networking-sbc-lynx.tar.bz2

You can now run the script, by passing the following parameters:

  • Device file of the microSD card (/dev/sdc in the example)
  • U-Boot image
  • Path of the directory containing the bootscript file, the Linux kernel image, and the device tree blob
  • Archive of the target's root file system (compressed as .tar.bz2 file).
sysadmin@stagesw:~/devel/sbclynx/uSD$ sudo ./mksd.sh /dev/sdc xuelk-1.1.3/xuelk-1.1.2_mx6ul_lynx_u-boot.imx xuelk-1.1.3 xuelk-1.1.3/xuelk-1.1.3_lynx-image-networking-sbc-lynx.tar.bz2 
[sudo] password for sysadmin: 
All data on /dev/sdc now will be destroyed! Continue? [y/n]
y
[Partitioning /dev/sdc...]
1024+0 records in
1024+0 records out
1048576 bytes (1.0 MB) copied, 3.65572 s, 287 kB/s
Disk /dev/sdc doesn't contain a valid partition table
DISK SIZE - 15976103936 bytes
Checking that no-one is using this disk right now ...
OK

Disk /dev/sdc: 1942 cylinders, 255 heads, 63 sectors/track

sfdisk: ERROR: sector 0 does not have an msdos signature
 /dev/sdc: unrecognized partition table type
Old situation:
No partitions found
New situation:
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start     End   #cyls    #blocks   Id  System
/dev/sdc1   *     10    1389    1380   11084850    c  W95 FAT32 (LBA)
/dev/sdc2       1390    1941     552    4433940   83  Linux
/dev/sdc3          0       -       0          0    0  Empty
/dev/sdc4          0       -       0          0    0  Empty
Successfully wrote the new partition table

Re-reading the partition table ...

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1)
to zero the first 512 bytes:  dd if=/dev/zero of=/dev/foo7 bs=512 count=1
(See fdisk(8).)
[Making filesystems...]
mkfs.vfat 3.0.12 (29 Oct 2011)
mke2fs 1.42 (29-Nov-2011)
Filesystem label=ROOTFS
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
277440 inodes, 1108485 blocks
55424 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1136656384
34 block groups
32768 blocks per group, 32768 fragments per group
8160 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done 

[Copying files...]
`xuelk-1.1.3/boot.scr' -> `/mnt/boot.scr'
`xuelk-1.1.3/imx6ul-lynx.dtb' -> `/mnt/imx6ul-lynx.dtb'
`xuelk-1.1.3/uImage' -> `/mnt/uImage'
`xuelk-1.1.3/xuelk-1.1.2_mx6ul_lynx_u-boot.imx' -> `/mnt/xuelk-1.1.2_mx6ul_lynx_u-boot.imx'
`xuelk-1.1.3/xuelk-1.1.3_lynx-image-networking-sbc-lynx.tar.bz2' -> `/mnt/xuelk-1.1.3_lynx-image-networking-sbc-lynx.tar.bz2'
[Extracting rfs (this may take a while...)]
[Programming u-boot.imx]
496+1 records in
496+1 records out
507948 bytes (508 kB) copied, 2.20883 s, 230 kB/s
[Done]



[1] In case you have a different size, you'll need to change the sfdisk parameters accordingly.