HRuessink 
I wanted to run Linux from the SD card on the mini6410, specifically I wanted to boot the kernel from the SD card and have the rootfs as a normal ext2/ext3 partition on the SD card (as opposed to a file that contains a rootfs). This post explains how I achieved that. Booting a linux kernel from the SD card is not a problem: The bootloader (Superboot or u-boot) will handle that, with the restriction that the kernel should be located on the first partitiion and this partition should be a FAT partition. As the first partition is used for allowing the bootloader to find and load the kernel, the ext2/ext3 rootfs must be placed on the second partition. My initial attempts to do this failed. I partitioned an SD card with two partitions: a FAT32 partition and a ext2 partition. The FAT partition contains the images directory containing the Linux/zImage kernel and a FriendlyARM.ini file. In the FriendlyARM.ini file I set the root= option to '/dev/mmcblk0p2, which points to the ext2 partition on the SD card. This failed with a message from the kernel that the device /dev/mmcblk0p2 did not exist. Digging into this I found out that the kernel comes with a minimal filesystem in memory: initrd/initramfs. This filesystem contains the device nodes that are necessary to access any devices before the root filesystem has been mounted, and these are also used to mount the root filesystem. Looking at the contents of this ramdisk filesystem I saw that it only contains a device for the first partition of the SD card. There was no device for the second partition, and this means that the kernel has no way of accessing it, and cannot mount it. The solution then was to add the device node to the initial ram filesystem. This involves recompiling the kernel. Below is the complete recipe for a Linux x86 based environment. The recipe assumes that you have downloaded and mounted the latest FriendlyARM DVDs (see the bottom of the download page at www.friendlyarm.net for username/password to download them from ftp.friendlyarm.net) and that you are using a shell prompt. You must also have sudo rights because root is required to create device nodes. Step 1. Toolchain and kernel sources Create a directory to work in and cd into this directory: $> mkdir FriendlyARM $> cd FriendlyARM Find the path to the Mini6410A DVD image and xtract the gcc cross-compiler and the kernel sources from the Linux directory : $> tar -zxf <dvd_path>/Linux/arm-linux-gcc-4.5.1-v6-vfp-20101103.tar.gz $> tar -zxf <dvd_path>/Linux/linux-2.6.36-20110112.tar.gz Also create a directory for the ram filessystem: $> mkdir initramfs You now have three directories: opt (toolchain), linux.2.6.36 (kernel sources) and initramfs Step 2. Configure the kernel Go into the kernel source directory and select a configuration that matches your display hardware: $> cd linux-2.6.36 $> cp config_mini6410_<type> .config I used the n43 version to match my 4.3" display. Start the configuration menu: $> make menuconfig [This requires ncurses. I had to install them on my Ubuntu workstation: 'sudo apt-get install libcdk5-dev'.] Select 'General setup' (at the top). Select the line that says: (arm-linux-) Cross-compiler tool prefix In the dialog change the string to the location of the GCC toolschain: <path_to_your_home>/FriendlyARM/opt/FriendlyARM/toolschain/4.5.1/bin/arm-n one-linux-gnueabi- Enter the absolute path to where you extracted the toolchain. Select OK, then scroll down to 'Initial RAM filesystem and RAM disk'. Select the line just below this, the one that reads: (scripts/FriendlyARM.cpio) Initramfs sourcefile(s) In the next dialog box, change the input to 'scripts/FriendlyARM_SD.cpio'. Click OK, then Exit and Exit to leave the configuration menu. Then select Yes to save the new configuration. Now build the tool that we need to create the contents of the ram filesystem. $> cd usr $> make gen_init_cpio Now return to the directory above: $> cd ../.. Step 3. Setup the ramdisk contents We will use the gen_init_cpio tool in the kernel sources to create the additional devices. The mknod command on the Linux host system may not be able to create the device nodes for the MMC device. Create a file that specifies the required device nodes for the SD card, for instance the following lines define device nodes for a second, third and fourth partition: $> > new_devices $> echo "nod dev/mmcblk0p2 0644 0 0 b 179 2" >> new_devices $> echo "nod dev/mmcblk0p3 0644 0 0 b 179 3" >> new_devices $> echo "nod dev/mmcblk0p4 0644 0 0 b 179 4" >> new_devices Extract the FriendlyARM ramdisk archive into the initramfs directory. Use sudo because extracting the archive will create device nodes: $> cd initramfs $> sudo cpio -id -F ../linux-2.6.36/scripts/FriendlyARM.cpio Use the definition file to add the new device nodes: $> ../linux-2.6.36/usr/gen_init_cpio ../new_devices | sudo cpio -id Check that this succeeded: $> ls -l dev total 0 crw-r--r-- 1 root root 5, 1 2011-02-14 14:56 console brw-r--r-- 1 root root 7, 0 2011-02-14 14:56 loop0 brw-r--r-- 1 root root 7, 1 2011-02-14 14:56 loop1 brw-r--r-- 1 root root 179, 1 2011-02-14 14:56 mmcblk0p1 brw-r--r-- 1 root root 179, 2 2011-02-14 15:36 mmcblk0p2 brw-r--r-- 1 root root 179, 3 2011-02-14 15:36 mmcblk0p3 brw-r--r-- 1 root root 179, 4 2011-02-14 15:36 mmcblk0p4 brw-r--r-- 1 root root 31, 0 2011-02-14 14:56 mtdblock0 brw-r--r-- 1 root root 31, 1 2011-02-14 14:56 mtdblock1 brw-r--r-- 1 root root 31, 2 2011-02-14 14:56 mtdblock2 crw-rw-rw- 1 root root 1, 3 2011-02-14 14:56 null If all is well, buld a new ramfs archive: $> find * | sudo cpio -H newc -o > ../linux-2.6.36/scripts/FriendlyARM_SD.cpio Go back to the directory above: $> cd .. Step 5. Compile the kernel and partition the SD card $> cd linux-2.6.36 $> make This will take awhile. In the meantime, partition an SD card and initialize the filesystems. The first partition should be a FAT partition of at least 5 MB. I used 20 MB just to be on the safe side. This partition will only hold the kernel and the FriendlyARM.ini file, so you don't need much space. The second partition should be a ext2 or ext3 file system (I understand that ext2 is easier on the SD card as the ext3 journalling writes every transaction in the same small buffer, wearing out the SD card more quickly). Use the SDflasher tool (in Windows) to flash the Superboot bootloader to the SD card. Step 6. Fill the SD card Make sure that you are still in the linux-2.6.36 directory. Attach the SD card to your linux workstation. This should mount two filesystems: the FAT filesystem (the boot partition) and the ext2 or ext3 filesystem (the root filesystem). Check where they are mounted using the 'mount'. On Ubuntu they are mounted under /media. Adapt the commands to where your partitions are mounted: $> mount [...] /dev/sdb2 on /media/Root type ext2 (rw,nosuid,nodev,uhelper=udisks) /dev/sdb1 on /media/BOOT type vfat (rw,nosuid,nodev,uhelper=udisks,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf 8=1,showexec,flush) Create the images directory on the BOOT partition, add the Linux subdirectory and copy the kernel to this directory: $> mkdir /media/BOOT/images $> mkdir /media/BOOT/images/Linux $> cp arch/arm/boot/zImage /media/BOOT/images/Linux/zImage_SD Add the file FriendlyARM.ini to /media/BOOT/images with the following minimalist content: #This line cannot be removed. by FriendlyARM(www.arm9.net) CheckOneButton=No Action=run OS= Linux VerifyNandWrite=No StatusType = Beeper| LED #################### Linux ##################### Linux-Kernel = Linux/zImage_SD Linux-CommandLine = root=/dev/mmcblk0p2 rootwait init=/sbin/init console=ttySAC0,115200 The boot options specifiy the rootfs device (/dev/mmcblk0p2), to wait until the root device becomes available (possibly not needed, as the card must be available because the kernel is loaded from the card), to start /sbin/init (depends on the kind of linux distribution that is put on the SD card) and the settings for the console. Go back to the directory FriendlyARM: $> cd .. To create the contents of the root filesystem I used the rootfs_qtopia_qt4.ext3 file from the Mini6410B DVD. First create a directory that will act as a mountpoint and mount the rootfs file as a loopback filesystem: $> mkdir rootfs $> sudo mount -o loop -t ext3 <dvd_path>/images/Linux/rootfs_qtopia_qt4.ext3 ./rootfs Now copy the contents to the second partition on the SD card: $> cd rootfs $> sudo find * | sudo cpio -ov | (cd /media/Root ; sudo cpio -idv) $> sync; sync This may take awhile. The sync command ensure that all write actions are completed. When this is done, safely eject the SD card and insert it in Mini6410. Connect a serial line to Mini6410 to monitor the boot process. Set the S2 switch (left side) to NOR (to the back) and turn on the Mini6410. The Mini6410 will now boot into Qtopia from the SD card with the screen calibration application (at least, on my touchscreen Mini6410).
