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== How to make your own rootfs ==
== How to make your own rootfs ==
[[How to make a debian rootfs for
[[How to make a debian rootfs for CI20]]
Revision as of 01:17, 13 August 2014
Everybody is welcome, and encouraged, to contribute back to the CI20 community, no matter how big or small their contribution is.
Contributions can come as small as a bug report, to some distro or Linux kernel work, to placing a whole new OS or distro on the board.
There are a number of ways to contribute, and a number of channels to help you along.
The linux kernel and u-boot sources for the CI20 are publically available on github.
The CI20 kernel source code is available on github.
There are presently two versions of the kernel
- the ci20-v3.0.8 kernel branch as shipped by default in the Debian NAND image derived directly from the Ingenic kernel source code releases.
- the latest kernel branch (ci20-v3.16 as of 08-08-2014) tracking mainline which is a nearly complete work in progress of upstreamable quality code to be soon pushed towards kernel.org. See details about this branch here CI20_upstream
Patches for the CI20 kernel and u-boot should be submitted to the CI20 mailing list for now.
Once the CI20 code is accepted into upstream repositories and mainline kernel.org then patches should go via the appropriate upstream mailing lists and maintainers as suggested by ./scripts/get_maintainer.pl.
The CI20 U-boot source is available on github
The ci20-v2013.10 branch of U-boot is the one shipped in the factory NAND image.
Bug reports for the CI20 are being taken via the github issue tracker linked to the CI20 kernel git repositories.
For linux kernel
Mailing list and Forum
The CI20 has a mailing list/forum via google groups
You can subscribe, even without a google account, by emailing (with a non-empty subject & body):
Or you can subscribe via your web browser by following the link below
CI20 also has an IRC channel #ci20 on freenode.net
NAND Flashing SD card
The NAND Flashing SD image creates an SD card that boots via mmc and writes the NAND of the CI20.
This can be used to restore the NAND on your CI20 to the factory default state, or upgrade the NAND image to a newer factory image file.
Note: Any changes you have made to your NAND (installed programs etc) will be irrecoverably lost during the NAND flash process. This will restore the CI20 NAND OS to the clean factory image state.
Making a NAND flashing SD card from the sd card image on Linux
1. Open a terminal
2. To determine the device name of the SD card, run lsblk which will list all block devices. Then insert the SD card, wait a few seconds, and run lsblk again. A new device plus any partitions should have appeared compared to the original list, the SD card will be the new top level device. Be sure that you have the right device name!
3. Unmount all partitions on the SD card. If the device name were sdx, this would be done with:
4. Write the image file with the following (replacing sdb with the correct device name):
dd if=debian6-20130815.img of=/dev/sdx
5. When it completes (note that dd will give no progress indication), run:
6. Remove the SD card.
7. Put SD card in CI20
8. Check the boot_sel switch is on the mmc boot mode.
9. Boot and wait for the LED to go from red to blue (nand writing) and then red!
10. The NAND has been flashed to factory default state. Power off the board. Remove the SD card. change the boot_sel switch to NAND boot mode. And boot the board.
Making a NAND flashing SD card from the sd card image on Windows
1. Download and run Win32DiskImager:
2. Insert the SD card, and select the image file and the drive letter for the SD card in Win32DiskImager. Win32DiskImager may not be able to see built-in SD card slots, so if it doesn't show up, use a USB adapter instead.
4. Click Write and wait for it to complete.
5. Close the imager and then remove the SD card.
6. Put SD card in CI20
7. Check the boot_sel switch is on the mmc boot mode.
8. Boot and wait for the LED to go from red to blue (nand writing) and then red!
9. The NAND has been flashed to factory default state. Power off the board. Remove the SD card. change the boot_sel switch to NAND boot mode. And boot the board.
To build the Kernel and U-Boot from sources you will need a MIPS toolchain, e.g. the Sourcery CodeBench toolchain, and u-boot-tools for mkimage
For the toolchain, use Sourcery CodeBench Lite 2013.11-36 for MIPS GNU/Linux available here
The Getting Started guide on the link above explains the install process
For u-boot-tools and mkimage run,
sudo apt-get install u-boot-tools
Building uboot from sources
Firstly, clone the U-Boot repositories from github. For U-Boot,
To build U-Boot:
git checkout ci20-v2013.10 make ARCH=mips CROSS_COMPILE=mips-linux-gnu- ci20_mmc make ARCH=mips CROSS_COMPILE=mips-linux-gnu-
Note, the CROSS_COMPILE for the toolchain path must be set in your environment.
This will generate 2 files, spl/u-boot-spl.bin and u-boot.img. We will use them in the next sections.
Building Linux Kernel from sources
For the Linux kernel, there are 2 branches that you can use:
ci20-v3.0.8: Default 3.0.8 kernel. All hardware supported. ci20-v3.xx: the latest kernel branch (3.16 as of 08-08-2014) tracking mainline which is a nearly complete work in progress of upstreamable quality code to be soon pushed towards kernel.orgFor details on driver support, check the github branch readme page. Note: various other branches might have wip-updates.
Clone the repository from github To build the kernel for 3.0.8 (change branch name accordingly):
git checkout ci20-v3.0.8 make ARCH=mips ci20_defconfig make ARCH=mips CROSS_COMPILE=mips-linux-gnu- uImage
Note, the CROSS_COMPILE for the toolchain path must be set in your environment. This will give you a uImage for the kernel (arch/mips/boot/uImage for 3.15 onwards, arch/mips/boot/compressed/uImage for 3.0.8).
Making a bootable SD card from sources
To make a bootable SD card, first partition your card with an MBR such that the first partition starts at an offset of no less than 270KB. To do that,
before and after plugging your sd card writer, to check which device is your sd card.
The following example considers the sd card writer to be loaded on /dev/sdx
The following command partitions your SD card (MAKE SURE GET THE SD CARD WRITER DEVICE CORRECT!). Paste it as is
sudo sfdisk /dev/sdx -uM -L << EOF 2,,L EOF
Then create an ext4 partition using
sudo mkfs.ext4 /dev/sdx1
Then install U-Boot SPL & the full U-Boot image to the card like so:
dd if=spl/u-boot-spl.bin of=/dev/sdx obs=512 seek=1 dd if=u-boot.img of=/dev/sdx obs=1K seek=14 sync
Mount the ext4 partition using
mount /dev/sdx1 /mnt
Then copy your kernel image to the ext4-formatted partition.
cp /path_to_uImage /mnt/boot/vmlinux.img sync
Unmount the sd card
At this point, the board will boot with u-boot and the kernel. But it will panic without a filesystem. You still need a rootfs.
You can use any existing tarball for a rootfs and extract it in the ext4 partition of the sd card. Or you can use buildroot
Buildroot is a small rootfs which can be easily loaded to the ram and runs from there. Note, if the filesystem is built as a ramdisk, no configuration is saved if rebooted.
We can use buildroot to build a ramdisk.
git clone git://git.busybox.net/buildroot buildroot cd buildroot make qemu_mipsel_malta_defconfig make menuconfig
The malta_defconfig is a good basic start and boots on the ci20.
Enable the following options in buildroot
Toolchain --> Toolchain type --> External toolchain (download or select path of your preinstalled toolchain) Filesystem images --> cpio the root filesystem Kernel --> <Disable the Linux kernel option. We built our own>
Exit and Save the configuration.
Once the build has finished, you should have an
file. Lets ignore it for now
To build the kernel with the Ramdisk, in the kernel sources directory, after the previous kernel compile instructions have been carried out.
make ARCH=mips CROSS_COMPILE=mips-linux-gnu- menuconfig
General setup --> Initial RAM filesystem and RAM disk (initramfs/initrd) support --> (/path_to_buildroot/arch/mips/boot/rootfs.cpio) Initramfs source files(s) Support initial ramdisks compressed using gzip ... Built-in initramfs compression mode --> gzip
Save and Exit.
make ARCH=mips CROSS_COMPILE=mips-linux-gnu- uImage
This will generate a uImage with the ramfs. The file should be larger than the usual 3-4mb kernel as it has a ramdisk built in.
Copy the uImage file to the sd card in the /boot/vmlinux.img
Boot the board and enjoy :)
Loading the Linux Kernel over ethernet via tftp
You can load the kernel over TFTP.
First, set up a tftp server by following any of the following links :
Copy the kernel image to the root of the TFTP server and
Boot the board with serial console. Stop the auto boot during uboot and then run:
env set serverip <server IP> dhcp 0x88000000 uImage bootm 0x88000000
You can set the bootcmd environment variable and save it to the SD card so that you will not need to type these commands each boot. For example:
env set serverip <server IP> env set bootcmd dhcp 0x88000000 uImage\; bootm 0x88000000 env save
This will configure automatic booting over TFTP. Note that the backslash before the semicolon is important.
How to make your own rootfs