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5.0 KiB
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97 lines
5.0 KiB
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Custom GCW Zero OS Image
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This page serves to record everything I've learned about building an OS Image for the GCW Zero.
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Existing Images
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===============
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- `The official image <http://gcw-zero.com/flashing>`_
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- This was last updated 2015-07-23
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- This is based on OpenDingux
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- `Current OpenDingux development images <https://github.com/OpenDingux/buildroot>`_
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- GCW Zero update packages, odboot binaries, and toolchains are available `here <https://github.com/OpenDingux/buildroot/releases>`_.
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- These are automatically? built by GitHub actions.
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- Work to bring OpenDingux / device support to newer Linux Kernel versions is supposedly happening in this repo
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- `Adam Image <https://github.com/eduardofilo/RG350_adam_image>`_
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- This is built on top of the newer OpenDingux releases.
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- Currently this seems to be fixed to a version from `2022-02-13 <https://github.com/eduardofilo/RG350_adam_image/blob/81b3e833640b8f1db69371dae47dabe248690dc9/build.sh#L6>`_.
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- This image opens up the OpenDingux image and creates a modified userspace with a different launcher and newer appliactions.
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- The boot flow seems to be identical to the OpenDingux upstream.
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Boot Flow
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=========
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`UBIBoot <https://github.com/pcercuei/UBIBoot>`_
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- Bootloader for launching a Linux Kernel off a UBI partition
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- This seems like it is used all over the place, but none of the images that I've looked at are using an UBI partition.
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- They have been FAT32
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- I should double check this, otherwise I'm a bit confused here.
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- Maybe all the SDCard images have this program written to their first 512 bytes (MBR style)
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- This would explain why the base offset for the ``/boot`` partition on the images is such a high number
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- Is there a UBI partition that launches before the kernel in the FAT32 partition is loaded?
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- This would probably not be visible when mounting the images
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- I should reinvestigate this
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- The Adam Image build scripts would probably be a good reference
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Kernel
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______
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- It is probably best to use the OpenDingux built kernel for now.
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- It looks like there is some upstreaming working being done, but the status of that in unknown.
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- It would be cool to extract this from the buildroot flow so it could be built independently.
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- One known issue with the latest OpenDingux kernel is that the display output doesn't work.
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- This seems to be due to a conflict in the HDMI driver.
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- I think disabling HDMI or removing the kernel module if there one might work around this.
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- This might be fixed now based on `this thread <https://github.com/eduardofilo/RG350_adam_image/issues/262>`_ on the Adam Image issue tracker.
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- I think this was a seperate issue based on the fact that the `fix <https://github.com/eduardofilo/RG350_adam_image/commit/f2c60849c90eb3ba6aab196604e8f66cce6b1d6e>`_ was in the Adam Image build scripts.
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- Adam Image is using too old of a OpenDingux base to have hit this issue, as it was discovered in May 2022 [1]_
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- One interesting tidbit from this thread is that the `OpenDingux maintainer seems to be working on fixing this issue <https://github.com/eduardofilo/RG350_adam_image/issues/262#issuecomment-1168830000>`_.
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- This is helpful, as the github issue that this same person opened has no replies. [1]_
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- This person might be overstating that the maintainer knowns, not sure here.
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`Mininit <https://github.com/OpenDingux/mininit>`_
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- Mininit is a bootloader that allows loading the root filesystem from a squashfs image called `rootfs.squashfs`.
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- It also supports loading kernel modules from a squashfs image called ``modules.squashfs``.
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- After it mounts all the required filesystems, control is handed off to the ``/sbin/init`` binary in the mounted rootfs [2]_.
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Booting Debian
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==============
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Creating a boot partition
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_________________________
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- TODO
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Creating a mips32le squashfs rootfs
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- `Docker based flow to build rootfs <https://git.ohea.xyz/gcwzero/debian-rootfs>`_
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Creating a sdcard image
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_______________________
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- TODO
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Packaging the Kernel as a ``.deb``
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__________________________________
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- TODO
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Packaging userspace applications as ``.deb`` files
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__________________________________________________
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- TODO
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Creating package repo for serving updates
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_________________________________________
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- TODO
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Useful Links
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============
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- `OpenDingux blog post on new kernel and device tree cleanup work <https://opendingux.net/opendingux/2020/06/09/update-on-gcw-zero-20200531.html>`_
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- `Dingoonity forum tutorial on building an image from scratch <https://boards.dingoonity.org/gcw-development/(guide)-build-firmware-from-source-and-flash-to-device/>`_
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- `Raspberry Pi automatic filesytem resize deep dive <https://gijs-de-jong.nl/posts/raspberry-pi-file-system-resize-on-first-boot/>`_
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Citations
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=========
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.. [1] https://github.com/OpenDingux/buildroot/issues/77
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.. [2] https://github.com/OpenDingux/mininit#rootfs-image-layout |