A Jetson Orin Nano 8GB developer kit running the r36.2 Jetson Developer Kit Operating Software fails while flashing an encrypted root filesystem to its 64Gb SD card. The decisive failure is not the repeated RTNETLINK message; the flash process attempts to access a block device that does not exist.
Identify the decisive flash error
blockdev: cannot open /dev/mmcblk3boot0: No such file or directory
l4t_flash_from_kernel: Starting to create gpt for emmc
Error: Could not stat device /dev/mmcblk3 - No such file or directory.
Flash failureSSH becomes ready before the failure, so the log confirms that flashing reaches the target-side kernel process. The fatal condition occurs when that process tries to create a GPT and cannot find /dev/mmcblk3. Treat the earlier RTNETLINK answers: File exists messages as secondary unless a complete log shows that they prevent connectivity.
Separate confirmed facts from the configuration hypothesis
| Evidence | Engineering conclusion |
|---|---|
| The developer kit has a 64Gb SD card and no NVMe device. | The selected flash configuration must describe the SD-backed storage actually exposed by the target. |
The script requests /dev/mmcblk3boot0 and /dev/mmcblk3. |
Those requested nodes are absent during the flash environment. |
| The log says it is creating a GPT for eMMC. | The active storage layout or target selection may not match the SD-card-only hardware. This is a hypothesis to confirm from the generated configuration and serial log. |
| The environment uses r36.2, identified in the evidence as a JetPack 6 Developer Preview context. | Do not assume production behavior or a later-release fix without testing a documented production release separately. |
Correct the storage geometry and target selection
- Capture the complete serial log during flashing. Confirm which block devices the recovery or initrd environment exposes before the failure.
- Inspect the selected external-storage configuration and generated flash index. Verify that they do not direct the process to an absent
/dev/mmcblk3device or an eMMC layout when the target contains only the SD card. - Specify
EXT_NUM_SECTORSfor the external storage as directed by the available product guidance. The evidence does not provide a valid numeric value, so derive it from the actual device geometry and the applicable image-generation documentation rather than guessing. - Regenerate the encrypted image and flash artifacts after correcting the storage selection and geometry; stale generated files may retain the previous target.
The evidence asks whether APP_ENC_SIZE is calculated automatically but does not answer that question. Check the generated layout and command output instead of assigning a manual value without documented sizing rules.
Verify the correction
A corrected run must stop requesting the missing /dev/mmcblk3 nodes, complete GPT creation on the intended SD-backed device, and proceed beyond item 62 in the active flash index. After boot, verify that the encrypted root filesystem resides on the intended storage. The cited HSM requirement concerns secure key generation, management, and factory transport; the evidence does not establish whether an HSM is technically required when using the supplied example script and example key for a proof of concept.
FAQ
Why does Jetson Orin Nano encrypted flashing report “Could not stat device /dev/mmcblk3”?
The flash environment cannot find /dev/mmcblk3. On the documented SD-card-only developer kit, verify that the flash configuration and generated index target the storage device actually exposed during recovery.
Do I need to set EXT_NUM_SECTORS for an encrypted Jetson external-storage flash?
The available guidance specifically directs this case to set EXT_NUM_SECTORS. Calculate it from the real storage geometry and applicable image layout; no supported numeric value is present in the evidence.
Is an HSM required to test Jetson disk encryption with the example key?
The documentation excerpt requires an HSM for secure key generation, management, and transport in a production workflow. The evidence does not confirm whether it is a runtime prerequisite for a proof-of-concept flash using the example script and key.
