Question about A and B partitions

[matthew141]

We believe we are seeing an A and B partition that are exactly the same when reviewing the stock partition map when flash a new disk image. Where can we find more information on these A and B partitions and is there a way to choose which one is being used during the boot process? Is there a redundancy feature that is currently being used that makes a decision on which one to use? I haven’t had any luck finding documentation on this. Currently using R35.3.1 and output of the partition map on the disk is shown below. Thanks!

Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
2 20.5kB 134MB 134MB A_kernel msftdata
3 134MB 135MB 786kB A_kernel-dtb msftdata
4 135MB 168MB 33.2MB A_reserved_on_user msftdata
5 168MB 302MB 134MB B_kernel msftdata
6 302MB 303MB 786kB B_kernel-dtb msftdata
7 303MB 336MB 33.2MB B_reserved_on_user msftdata
8 336MB 420MB 83.9MB recovery msftdata
9 420MB 421MB 524kB recovery-dtb msftdata
10 421MB 488MB 67.1MB fat32 esp boot, esp
11 488MB 572MB 83.9MB recovery_alt msftdata
12 572MB 572MB 524kB recovery-dtb_alt msftdata
13 572MB 639MB 67.1MB esp_alt msftdata
14 639MB 1059MB 419MB UDA msftdata
15 1059MB 1562MB 503MB reserved msftdata
1 1562MB 63.7GB 62.1GB ext4 APP msftdata

[KevinFFF]

Hi matthew141,

Are you using the devkit or custom board for AGX Orin?

From the result your shared, it seems you don’t enable redundant rootfs currently.
Please note that A/B bootchain is enabled by default but A/B rootfs is disabled by default.

For A/B bootchain, you can refer to Update and Redundancy — Jetson Linux Developer Guide documentation (nvidia.com).
For redundant rootfs, you can refer to Root File System Redundancy.

You can also run the following command to check the slot status.

$ sudo nvbootctrl dump-slots-info
$ sudo nvbootctrl -t rootfs dump-slots-info