How to flash only the kernel and device tree when using the initrd flash method

Autonomous Machines Jetson & Embedded Systems Jetson TX2
1

I’m looking for a way to flash the kernel and device tree to the TX2 NX. We’re using the initrd flash method for its ROOTFS_AB support and up until now we’re flashing the entire device in one hit using:

ROOTFS_AB=1 ./tools/kernel_flash/l4t_initrd_flash.sh --flash-only --external-device sda1 -S 40GiB -c ./tools/kernel_flash/flash_l4t_nvme_rootfs_ab.xml jetson-xavier-nx-devkit-tx2-nx external

The problem we’ve having now is that we need to be able to do a kernel and device tree update without updating the entire root filesystem. I’ve read through the README_initrd_flash.txt but I wasn’t able to find a way to do this.

Can anyone suggest how to go about this?

3

hello zsaleeba,

you should be able to enable “-k” option, initrd flash can flash one partition based on the partition label specified in the index file.
may I also confirm the JetPack release version you’re currently working with, thanks

4

We’re using JetPack 4.6.2.

Since we have an A-B boot setup we have quite a few partitions:

Number  Start   End     Size    File system  Name               Flags
 1      20.5kB  42.9GB  42.9GB  ext4         APP                msftdata
 2      42.9GB  85.9GB  42.9GB  ext4         APP_b              msftdata
 3      85.9GB  86.0GB  67.1MB               kernel             msftdata
 4      86.0GB  86.0GB  67.1MB               kernel_b           msftdata
 5      86.0GB  86.0GB  459kB                kernel-dtb         msftdata
 6      86.0GB  86.0GB  459kB                kernel-dtb_b       msftdata
 7      86.0GB  86.1GB  66.1MB               recovery           msftdata
 8      86.1GB  86.1GB  524kB                recovery-dtb       msftdata
 9      86.1GB  86.1GB  262kB                kernel-bootctrl    msftdata
10      86.1GB  86.1GB  262kB                kernel-bootctrl_b  msftdata
11      86.1GB  86.2GB  105MB                RECROOTFS          msftdata
12      86.2GB  500GB   414GB   ext4         UDA                msftdata

Is it sufficient to replace the contents of the active ‘kernel’ and ‘kernel-dtb’ partitions with the kernel ‘Image’ file and ‘tegra186-p3636-0001-p3509-0000-a01.dtb’ respectively? Is there anything else which needs to be done?

Can I just ‘dd’ the files on to these partitions instead of using the l4t_initrd_flash.sh flash script if I’m doing an OTA to the device and need to run the update locally rather than via USB?

5

hello zsaleeba,

you cannot dd them directly, since those binary files were sign/encrypted before flashing into partitions.
however, you may try running flash script with --no-flash to generate sign/encrypted files, then you’ll able copy them with dd utility.

6

Word of caution: When using dd to fill in a partition, especially a signed partition (where the signature can add a few bytes), make sure the partition is large enough to hold the dd content.

7

Thanks. I’ll keep that in mind.

9

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