Jetson Nano EMMC How to boot from External SD Card?

We have flashed our EMMC module using the instructions located here:

Using the B01 board.

It has successfully flashed the EMMC, and the EMMC now boots to a shell.

I have couple questions:

  1. How do we identify if the EMMC is detecting the external SD slot or the presence of an SD Card ?

  2. What are the precise steps to get the External SD Card to boot, instead of the EMMC ?

We have very little available shell commands on the EMMC right now


I don’t think the eMMC model has software to boot from SD card. What you’ll probably end up having to do is put everything except the rootfs on eMMC, and then direct rootfs to mount the SD card rootfs. The non-eMMC dev kit model has QSPI memory which does not exist on the eMMC model, and that content is for booting an SD card. The question is whether you really need everything to boot from SD card, or if you are ok with just the rootfs being on the SD card? The former is probably not possible, and the latter is probably (relatively speaking) simple (though I suppose it is possible it might involve an initrd, but also might not).


Thanks for the help.

We have the EMMC and only need the External SD Card mounted as data, not for booting.

Can you please let us know the steps to detect and mount the External SD Card as a data drive.


Your question actually indicates two different topics.

The first one is how to enable the external sdcard on the board.

The second one is how to mount file system on it.

For the first one, please search sdmmc3 as keywords in this forum. And you shall find answers.

I can’t help with the detect part, but if the SD card shows up, then mounting partitions will be no different on a Jetson versus any other Linux system. You would probably want to mention a specific use-case of how you want to use the SD card mount to correctly answer the mount question. I say this because auto mount might already work as you want it, but if you want this to be mounted in a specific place, then that would be another step. If you want this to not interfere with boot when it is missing, then that too needs to be known (due to different mount options).

If you mount it via a USB SD card adapter then it will likely show up as /dev/sda. Then you can create a partition on this with something like

fdisk /dev/sda

Then create a file system on it with

mkfs -t ext4 /dev/sda1

Then you can mount that or add an entry to /etc/fstab if you like.

Kim Hendrikse

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