[DEV] Ubuntu 18.04 LTS Bionic (Linux for Tegra) for SHIELD Android TV

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yifanlu

Senior Member
Aug 1, 2011
274
227
This is a full featured port of NVIDIA L4T R32.7.2 (Ubuntu 18.04) for the SHIELD TV (2015, 2017). It has full hardware support including:

  • GPU acceleration
  • Wifi/Bluetooh
  • USB 3.0
  • HDMI with audio
  • microSD (supported models)
  • Power management
  • etc

Download​

Download Latest (R32.7.2, 07/09/22)

Details​

The main challenge in this port was getting the right kernel version to match with the on-device DTB. The DTB is structured in a way that Cboot must be able to parse (and modify it) and then Linux kernel must be able to parse it as well. There are various issue with previous documented methods of flashing a Jetson DTB. NVIDIA stopped distributing SHIELD TV (Foster) DTBs with L4T releases years ago so you would have to manually port a newer DTB or be stuck with an older kernel. Flashing an (years) older DTB is not an option because a newer Cboot will fail to parse it and you'll end up with a brick. Flashing a custom DTB is dangerous for this reason as well. Flashing an older Cboot is not possible due to signature requirements even on an unlocked device. So we are stuck with one option: build a L4T kernel around the device's Android DTB.

NVIDIA maintains two forks of Linux for Tegra X1. The L4T kernel and the Android (downstream) kernel are not 1-to-1 compatible. DTB property names can differ, ioctl structure sizes can differ, etc. I tried various ways to cleanly merge the two and ended up with the following working strategy:

  • Kernel 4.9 + NVIDIA drivers from Android fork
  • Build config from L4T release hand merged with options from the Android TV kernel
  • NVGPU drivers from L4T fork (due to lack of source for and need for compatibility with userland drivers)
  • Initramfs from L4T release

I also had to port some patches from one fork to the other (especially for NVGPU). The end result is a kernel that combines both forks and therefore is relatively stable and fully featured.

Booting​


The build is tested with the 9.0.0 and 9.1.0 release. It is recommended that you update to 9.0.0.

Note that once you update Cboot, you cannot downgrade to a lower version anymore! If you do not update, some things may not work properly due to the DTB differences noted above however, any relatively "modern" build may still work.

You need a USB drive with at least 8GB of free space. Flash rootfs.img to the first partition (replace sdX1 with your USB drive partition):

Code:
$ sudo dd if=rootfs.img of=/dev/sdX1 bs=1MiB

Make sure your SHIELD TV is unlocked and connected to fastboot.

Either boot the kernel directly:

Code:
$ fastboot boot boot.img

Or you may also flash the kernel if you want to:

Code:
$ fastboot flash boot boot.img
$ fastboot reboot

The initramfs will attempt to boot from the following devices (in order):

1. sda1: First partition of external USB on 16GB model
2. sdb1: First partition of external USB on 500GB model
3. mmcblk2p1: First partition of microSD on supported models
4. mmcblk0p29: Userdata partition of eMMC on 16GB model
5. sda32: Userdata partition of HDD on 500GB model
6. sda33: Partition 33 of HDD on 500GB model (partition table modification needed)
7. sda34: Partition 34 of HDD on 500GB model (partition table modification needed)
8. mmcblk0p19: System partition of eMMC on 16GB model (too small to hold rootfs unless partition table is modified)

After installation, you should resize the partition if your device is > 8GB (replace sdX1 with your installation device).

Code:
$ sudo e2fsck -f /dev/sdX1
$ sudo resize2fs /dev/sdX1

Flashing to internal eMMC​


If you wish to flash rootfs to your internal eMMC, you need to first install to a USB and boot into Ubuntu. Flashing from fastboot will NOT work due to some eMMC issues (I think Cboot does not respect the block remap).

The following will flash to the userdata partition and will WIPE any existing data on the device!

Code:
$ sudo dd if=rootfs.img of=/dev/mmcblk0p29 bs=1MiB
$ sudo e2fsck -f /dev/mmcblk0p29
$ sudo resize2fs /dev/mmcblk0p29

You can follow similar steps to flash to sda32 on a 500GB model. Follow the steps in the first section to flash boot.img.

Uninstalling​


As long as you didn't touch the other partitions, you can easily restore Android TV with the recovery images.

Code:
$ fastboot erase userdata
$ fastboot flash boot nv-recovery-image-shield-atv-9.0.0/boot.img

Troubleshooting​

The USB/microSD does not boot and is stuck at a blinking cursor
  1. Make sure you wait long enough (at least five minutes).
  2. Make sure your USB drive (or microSD) is formatted with MBR with a single partition. You should be writing to /dev/sdX1 (X is some letter) with a "1" at the end. Do not write to /dev/sdX.
  3. Try to mark the first partition as bootable.
 
Last edited:

yifanlu

Senior Member
Aug 1, 2011
274
227

Manual Build​

Download Latest (R32.7.2, 07/09/22)

Prerequisite​


Building the kernel​


1. Install the toolchain.

Code:
$ wget -O toolchain.tar.xz https://developer.nvidia.com/embedded/dlc/l4t-gcc-7-3-1-toolchain-64-bit
$ tar xpf toolchain.tar.xz
$ sudo mv gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu /opt/l4t-toolchain

2. Fetch the SHIELD TV Android kernel sources.

Code:
$ git clone --depth 1 https://nv-tegra.nvidia.com/r/linux-4.9.git -b rel-shield-r-9.0.2-opensource-4.9 linux-4.9
$ git clone --depth 1 https://nv-tegra.nvidia.com/r/linux-nvidia.git -b rel-shield-r-9.0.2-opensource nvidia

3. Fetch the Linux For Tegra NVGPU sources.

Code:
$ wget https://developer.nvidia.com/embedded/l4t/r32_release_v7.2/sources/t210/public_sources.tbz2
$ tar xpf public_sources.tbz2
$ tar xpf Linux_for_Tegra/source/public/kernel_src.tbz2
$ mv kernel/nvgpu nvgpu

You should have three directories: linux-4.9, nvidia, and nvgpu

4. Patch the sources.

Code:
$ cat patches/kernel-4.9/*.patch | patch -p1 -dlinux-4.9
$ cat patches/nvidia/*.patch | patch -p1 -dnvidia
$ cat patches/nvgpu/*.patch | patch -p1 -dnvgpu

5. Build the kernel and install the modules.

Code:
$ export CROSS_COMPILE=/opt/l4t-toolchain/bin/aarch64-linux-gnu-
$ export ARCH=arm64
$ mkdir -p Linux_for_Tegra/rootfs/
$ pushd linux-4.9
$ make shieldtv_defconfig
$ make -j$(nproc) zImage
$ make -j$(nproc) modules
$ make modules_install INSTALL_MOD_PATH=../Linux_for_Tegra/rootfs/
$ sudo chown -R root:root ../Linux_for_Tegra/rootfs/lib
$ popd

Building Root Filesystem​


1. Extract jetson-210_linux_r32.7.2_aarch64.tbz2 and tegra_linux_sample-root-filesystem_r32.7.2_aarch64.tbz2.

Code:
$ tar xpf jetson-210_linux_r32.7.2_aarch64.tbz2
$ pushd Linux_for_Tegra/rootfs/
$ sudo tar xpf ../../tegra_linux_sample-root-filesystem_r32.7.2_aarch64.tbz2
$ sudo touch etc/nv_boot_control.conf

Note the use of sudo for the last two commands. This is required for file permissions to be correct. The touch at the end resolves a bug in NVIDIA's code that resulted in the installer not launching.

2. Install the filesystem.

Code:
$ cd ..
$ sudo ./apply_binaries.sh
$ popd

3. To enable Wifi and NVDEC, need to first convert vendor.img downlaoded from the SHIELD recovery image to an ext4 image.

Code:
$ simg2img nv-recovery-image-shield-atv-9.0.0/vendor.img vendor-raw.img

4. Next mount the image.

Code:
$ mkdir vendor
$ sudo mount -o loop vendor-raw.img vendor

5. Copy the firmware over.

Code:
$ sudo cp vendor/firmware/bcmdhd_clm_foster.blob Linux_for_Tegra/rootfs/lib/firmware/brcm/bcmdhd.clm_blob
$ sudo cp vendor/firmware/fw_bcmdhd.bin Linux_for_Tegra/rootfs/lib/firmware/brcm/fw_bcmdhd.bin
$ sudo cp vendor/firmware/nvram_foster_e_4354.txt Linux_for_Tegra/rootfs/lib/firmware/brcm/nvram.txt
$ sudo cp vendor/firmware/tegra21x/* Linux_for_Tegra/rootfs/lib/firmware/tegra21x/
$ sudo cp vendor/firmware/tegra21x/vic04_ucode.bin Linux_for_Tegra/rootfs/lib/firmware/nvidia/tegra210/
$ sudo umount vendor

6. Create and mount a new ext4 image. Note that we will create 8GiB image which should be enough to hold the root filesystem. After you flash it to your device and boot successfully, you'll want to run resize2fs.

Code:
$ dd if=/dev/zero of=rootfs.img bs=1MiB count=8196
$ mkfs.ext4 rootfs.img
$ mkdir mount
$ sudo mount -o loop rootfs.img mount

7. Copy the filesystem to the disk image.

Code:
$ sudo mv Linux_for_Tegra/rootfs/* mount/
$ sudo umount mount

Building boot image​


1. Extract the existing initramfs.

Code:
$ mkdir initramfs
$ pushd initramfs
$ cat Linux_for_Tegra/bootloader/l4t_initrd.img | gunzip -c | cpio -i

2. Patch init.

Code:
$ cp patches/initramfs/init init

3. Rebuild the image.

Code:
$ find ./ | cpio -H newc -o -R root:root | gzip -9 -c > ../initramfs.img

4. Build boot.img

Code:
$ abootimg --create boot.img -f patches/bootimg.cfg -k linux-4.9/arch/arm64/boot/zImage -r initramfs.img
 
Last edited:

yifanlu

Senior Member
Aug 1, 2011
274
227
I've updated the download to fix an issue I found with connecting to 5GHz wifi. Using the other nvram.txt fixed it. I also noticed that NVENC/NVDEC doesn't work properly and am unsure if it's a kernel issue or a L4T issue. I tried building with nvdec bootloader disabled and used L4T's ns firmware and it still didn't work.

EDIT: Made another update to fix the NVENC/NVDEC issue. Additionally, the led lightbar control driver is added in. I also made the following systemd script to disable the lightbar at boot.

Code:
[Unit]
Description=Disable the lightbar
After=multi-user.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStartPre=-/bin/sh -c "/sbin/rmmod leds-cy8c && /sbin/modprobe leds-cy8c"
ExecStart=/bin/sh -c "echo 0 > /sys/class/leds/led_lightbar/brightness"
ExecStop=/bin/sh -c "echo 255 > /sys/class/leds/led_lightbar/brightness"

[Install]
WantedBy=multi-user.target
 
Last edited:

EgomafiaX

New member
Jul 17, 2022
2
0
Is this a fully working ubuntu desktop OS experience or is this a Kernel for the shield?
 

yifanlu

Senior Member
Aug 1, 2011
274
227
Is this a fully working ubuntu desktop OS experience or is this a Kernel for the shield?
Full Ubuntu 18.04, it’s not just a kernel. I’ve been using it for the past week and haven’t run into any issues so far. You can try it out without modifying anything by flashing rootfs.img to a usb drive and booting the kernel from fastboot.
 
  • Like
Reactions: EgomafiaX

EgomafiaX

New member
Jul 17, 2022
2
0
Very Interesting, I just got my shield last week and i wanna try some few things on it. Don’t have any experience with flashing whatsoever
 

moshtin

New member
Aug 24, 2022
1
0
What's performance like? I was thinking of buying a new SBC but this could be just what I am looking for
 

pcabarat

New member
Sep 5, 2022
4
0
Hi!
Thanks for your work.
This seems promising. Any chance anything similar should work on SHIELD TV Pro (2019)?
I compared recovery images provided by NVIDIA and I did not come across many differences between vendor binaries so I guess there is won't be any issue with the roottfs and kernel.
However on the SHIELD TV Pro, the boot.img is twice as big and the recovery image seems to contain a DTB image (mdarcy.dtb.img) and a vbmeta.img. I suspect the boot process to be somewhat different on this plateform.
Did anyone manage to get anything working on a SHIELD TV Pro?
 

pcabarat

New member
Sep 5, 2022
4
0
Also the shieldtv_defconfig is located in arm/ instead of arm64/ in the patches you provide.
 

chaitan3

New member
Dec 13, 2010
3
0
I tried the instructions from the first post on a Shield TV (2017) model and after doing "fastboot boot boot.img" the screen goes black with a blinking underscore on the top left and gets stuck there.

Any idea on what could be wrong? I dd'ed the rootfs.img to a usb stick attached to the usb port adjacent to the hdmi port. The usb A->A cable for fastboot/adb is attached to the usb port away from the hdmi cable.
 

kihmathi

New member
Apr 23, 2016
4
0
I tried the instructions from the first post on a Shield TV (2017) model and after doing "fastboot boot boot.img" the screen goes black with a blinking underscore on the top left and gets stuck there.

Any idea on what could be wrong? I dd'ed the rootfs.img to a usb stick attached to the usb port adjacent to the hdmi port. The usb A->A cable for fastboot/adb is attached to the usb port away from the hdmi cable.
I also seem to have hit same roadblock, did you succed with this.
 

yifanlu

Senior Member
Aug 1, 2011
274
227
I only have a 2015 shieldtv but I read the hardware are the same. Maybe I was wrong and there’s some kernel changes needed. I would diff the defconfig between the latest android release for both and see what the differences are. Then add those to the config.

EDIT: I downloaded the recovery image for 2017 and compared the kernel defconfig and it’s identical. That means the kernel isn’t the issue. My next guess would be the init script I wrote. Maybe the dev number is different on 2017?
 
Last edited:

yifanlu

Senior Member
Aug 1, 2011
274
227
In my init script, I wait 10s for the root device to show up before giving up and trying the next one. Perhaps this isn’t long enough?

If you update the init file inside the initramfs, there is on line 71 “while [ ${count} -lt 20 ]” maybe change that to “while [ ${count} -lt 100 ]” to try 100 times (with 0.2s in between).
 

kaytoo

New member
Jun 9, 2012
1
0
OnePlus 6T
In my init script, I wait 10s for the root device to show up before giving up and trying the next one. Perhaps this isn’t long enough?

If you update the init file inside the initramfs, there is on line 71 “while [ ${count} -lt 20 ]” maybe change that to “while [ ${count} -lt 100 ]” to try 100 times (with 0.2s in between).

I tried this on my 2017 shield, didn't fix the issue, there is a blinking underscore on the top left. Is there any way to get logs, or show some debug messages on the screen?
 

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  • 7
    This is a full featured port of NVIDIA L4T R32.7.2 (Ubuntu 18.04) for the SHIELD TV (2015, 2017). It has full hardware support including:

    • GPU acceleration
    • Wifi/Bluetooh
    • USB 3.0
    • HDMI with audio
    • microSD (supported models)
    • Power management
    • etc

    Download​

    Download Latest (R32.7.2, 07/09/22)

    Details​

    The main challenge in this port was getting the right kernel version to match with the on-device DTB. The DTB is structured in a way that Cboot must be able to parse (and modify it) and then Linux kernel must be able to parse it as well. There are various issue with previous documented methods of flashing a Jetson DTB. NVIDIA stopped distributing SHIELD TV (Foster) DTBs with L4T releases years ago so you would have to manually port a newer DTB or be stuck with an older kernel. Flashing an (years) older DTB is not an option because a newer Cboot will fail to parse it and you'll end up with a brick. Flashing a custom DTB is dangerous for this reason as well. Flashing an older Cboot is not possible due to signature requirements even on an unlocked device. So we are stuck with one option: build a L4T kernel around the device's Android DTB.

    NVIDIA maintains two forks of Linux for Tegra X1. The L4T kernel and the Android (downstream) kernel are not 1-to-1 compatible. DTB property names can differ, ioctl structure sizes can differ, etc. I tried various ways to cleanly merge the two and ended up with the following working strategy:

    • Kernel 4.9 + NVIDIA drivers from Android fork
    • Build config from L4T release hand merged with options from the Android TV kernel
    • NVGPU drivers from L4T fork (due to lack of source for and need for compatibility with userland drivers)
    • Initramfs from L4T release

    I also had to port some patches from one fork to the other (especially for NVGPU). The end result is a kernel that combines both forks and therefore is relatively stable and fully featured.

    Booting​


    The build is tested with the 9.0.0 and 9.1.0 release. It is recommended that you update to 9.0.0.

    Note that once you update Cboot, you cannot downgrade to a lower version anymore! If you do not update, some things may not work properly due to the DTB differences noted above however, any relatively "modern" build may still work.

    You need a USB drive with at least 8GB of free space. Flash rootfs.img to the first partition (replace sdX1 with your USB drive partition):

    Code:
    $ sudo dd if=rootfs.img of=/dev/sdX1 bs=1MiB

    Make sure your SHIELD TV is unlocked and connected to fastboot.

    Either boot the kernel directly:

    Code:
    $ fastboot boot boot.img

    Or you may also flash the kernel if you want to:

    Code:
    $ fastboot flash boot boot.img
    $ fastboot reboot

    The initramfs will attempt to boot from the following devices (in order):

    1. sda1: First partition of external USB on 16GB model
    2. sdb1: First partition of external USB on 500GB model
    3. mmcblk2p1: First partition of microSD on supported models
    4. mmcblk0p29: Userdata partition of eMMC on 16GB model
    5. sda32: Userdata partition of HDD on 500GB model
    6. sda33: Partition 33 of HDD on 500GB model (partition table modification needed)
    7. sda34: Partition 34 of HDD on 500GB model (partition table modification needed)
    8. mmcblk0p19: System partition of eMMC on 16GB model (too small to hold rootfs unless partition table is modified)

    After installation, you should resize the partition if your device is > 8GB (replace sdX1 with your installation device).

    Code:
    $ sudo e2fsck -f /dev/sdX1
    $ sudo resize2fs /dev/sdX1

    Flashing to internal eMMC​


    If you wish to flash rootfs to your internal eMMC, you need to first install to a USB and boot into Ubuntu. Flashing from fastboot will NOT work due to some eMMC issues (I think Cboot does not respect the block remap).

    The following will flash to the userdata partition and will WIPE any existing data on the device!

    Code:
    $ sudo dd if=rootfs.img of=/dev/mmcblk0p29 bs=1MiB
    $ sudo e2fsck -f /dev/mmcblk0p29
    $ sudo resize2fs /dev/mmcblk0p29

    You can follow similar steps to flash to sda32 on a 500GB model. Follow the steps in the first section to flash boot.img.

    Uninstalling​


    As long as you didn't touch the other partitions, you can easily restore Android TV with the recovery images.

    Code:
    $ fastboot erase userdata
    $ fastboot flash boot nv-recovery-image-shield-atv-9.0.0/boot.img

    Troubleshooting​

    The USB/microSD does not boot and is stuck at a blinking cursor
    1. Make sure you wait long enough (at least five minutes).
    2. Make sure your USB drive (or microSD) is formatted with MBR with a single partition. You should be writing to /dev/sdX1 (X is some letter) with a "1" at the end. Do not write to /dev/sdX.
    3. Try to mark the first partition as bootable.
    3
    I've updated the download to fix an issue I found with connecting to 5GHz wifi. Using the other nvram.txt fixed it. I also noticed that NVENC/NVDEC doesn't work properly and am unsure if it's a kernel issue or a L4T issue. I tried building with nvdec bootloader disabled and used L4T's ns firmware and it still didn't work.

    EDIT: Made another update to fix the NVENC/NVDEC issue. Additionally, the led lightbar control driver is added in. I also made the following systemd script to disable the lightbar at boot.

    Code:
    [Unit]
    Description=Disable the lightbar
    After=multi-user.target
    
    [Service]
    Type=oneshot
    RemainAfterExit=yes
    ExecStartPre=-/bin/sh -c "/sbin/rmmod leds-cy8c && /sbin/modprobe leds-cy8c"
    ExecStart=/bin/sh -c "echo 0 > /sys/class/leds/led_lightbar/brightness"
    ExecStop=/bin/sh -c "echo 255 > /sys/class/leds/led_lightbar/brightness"
    
    [Install]
    WantedBy=multi-user.target
    2

    Manual Build​

    Download Latest (R32.7.2, 07/09/22)

    Prerequisite​


    Building the kernel​


    1. Install the toolchain.

    Code:
    $ wget -O toolchain.tar.xz https://developer.nvidia.com/embedded/dlc/l4t-gcc-7-3-1-toolchain-64-bit
    $ tar xpf toolchain.tar.xz
    $ sudo mv gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu /opt/l4t-toolchain

    2. Fetch the SHIELD TV Android kernel sources.

    Code:
    $ git clone --depth 1 https://nv-tegra.nvidia.com/r/linux-4.9.git -b rel-shield-r-9.0.2-opensource-4.9 linux-4.9
    $ git clone --depth 1 https://nv-tegra.nvidia.com/r/linux-nvidia.git -b rel-shield-r-9.0.2-opensource nvidia

    3. Fetch the Linux For Tegra NVGPU sources.

    Code:
    $ wget https://developer.nvidia.com/embedded/l4t/r32_release_v7.2/sources/t210/public_sources.tbz2
    $ tar xpf public_sources.tbz2
    $ tar xpf Linux_for_Tegra/source/public/kernel_src.tbz2
    $ mv kernel/nvgpu nvgpu

    You should have three directories: linux-4.9, nvidia, and nvgpu

    4. Patch the sources.

    Code:
    $ cat patches/kernel-4.9/*.patch | patch -p1 -dlinux-4.9
    $ cat patches/nvidia/*.patch | patch -p1 -dnvidia
    $ cat patches/nvgpu/*.patch | patch -p1 -dnvgpu

    5. Build the kernel and install the modules.

    Code:
    $ export CROSS_COMPILE=/opt/l4t-toolchain/bin/aarch64-linux-gnu-
    $ export ARCH=arm64
    $ mkdir -p Linux_for_Tegra/rootfs/
    $ pushd linux-4.9
    $ make shieldtv_defconfig
    $ make -j$(nproc) zImage
    $ make -j$(nproc) modules
    $ make modules_install INSTALL_MOD_PATH=../Linux_for_Tegra/rootfs/
    $ sudo chown -R root:root ../Linux_for_Tegra/rootfs/lib
    $ popd

    Building Root Filesystem​


    1. Extract jetson-210_linux_r32.7.2_aarch64.tbz2 and tegra_linux_sample-root-filesystem_r32.7.2_aarch64.tbz2.

    Code:
    $ tar xpf jetson-210_linux_r32.7.2_aarch64.tbz2
    $ pushd Linux_for_Tegra/rootfs/
    $ sudo tar xpf ../../tegra_linux_sample-root-filesystem_r32.7.2_aarch64.tbz2
    $ sudo touch etc/nv_boot_control.conf

    Note the use of sudo for the last two commands. This is required for file permissions to be correct. The touch at the end resolves a bug in NVIDIA's code that resulted in the installer not launching.

    2. Install the filesystem.

    Code:
    $ cd ..
    $ sudo ./apply_binaries.sh
    $ popd

    3. To enable Wifi and NVDEC, need to first convert vendor.img downlaoded from the SHIELD recovery image to an ext4 image.

    Code:
    $ simg2img nv-recovery-image-shield-atv-9.0.0/vendor.img vendor-raw.img

    4. Next mount the image.

    Code:
    $ mkdir vendor
    $ sudo mount -o loop vendor-raw.img vendor

    5. Copy the firmware over.

    Code:
    $ sudo cp vendor/firmware/bcmdhd_clm_foster.blob Linux_for_Tegra/rootfs/lib/firmware/brcm/bcmdhd.clm_blob
    $ sudo cp vendor/firmware/fw_bcmdhd.bin Linux_for_Tegra/rootfs/lib/firmware/brcm/fw_bcmdhd.bin
    $ sudo cp vendor/firmware/nvram_foster_e_4354.txt Linux_for_Tegra/rootfs/lib/firmware/brcm/nvram.txt
    $ sudo cp vendor/firmware/tegra21x/* Linux_for_Tegra/rootfs/lib/firmware/tegra21x/
    $ sudo cp vendor/firmware/tegra21x/vic04_ucode.bin Linux_for_Tegra/rootfs/lib/firmware/nvidia/tegra210/
    $ sudo umount vendor

    6. Create and mount a new ext4 image. Note that we will create 8GiB image which should be enough to hold the root filesystem. After you flash it to your device and boot successfully, you'll want to run resize2fs.

    Code:
    $ dd if=/dev/zero of=rootfs.img bs=1MiB count=8196
    $ mkfs.ext4 rootfs.img
    $ mkdir mount
    $ sudo mount -o loop rootfs.img mount

    7. Copy the filesystem to the disk image.

    Code:
    $ sudo mv Linux_for_Tegra/rootfs/* mount/
    $ sudo umount mount

    Building boot image​


    1. Extract the existing initramfs.

    Code:
    $ mkdir initramfs
    $ pushd initramfs
    $ cat Linux_for_Tegra/bootloader/l4t_initrd.img | gunzip -c | cpio -i

    2. Patch init.

    Code:
    $ cp patches/initramfs/init init

    3. Rebuild the image.

    Code:
    $ find ./ | cpio -H newc -o -R root:root | gzip -9 -c > ../initramfs.img

    4. Build boot.img

    Code:
    $ abootimg --create boot.img -f patches/bootimg.cfg -k linux-4.9/arch/arm64/boot/zImage -r initramfs.img
    1
    Is this a fully working ubuntu desktop OS experience or is this a Kernel for the shield?
    Full Ubuntu 18.04, it’s not just a kernel. I’ve been using it for the past week and haven’t run into any issues so far. You can try it out without modifying anything by flashing rootfs.img to a usb drive and booting the kernel from fastboot.