Read Only FS for jetson Nano

Hi All,

I’m trying to finalize my production Jetson Nano by making the eMMC read-only. I’m running on R32 (release), REVISION: 5.1, GCID: 27362550, BOARD: t210ref, EABI: aarch64, DATE: Wed May 19 18:07:59 UTC 2021, JetPack 4.6.

Searching the forums I can see that OverlayFS is the chosen method for making things read-only, but I was wondering if anyone (recently) has had any success with just mounting the disk in ro without using overlayfs.

hello an_actual_toaster,

suggest you check Topic 1032951 , and also Using the initial RAM disk (initrd) for reference.

there’s an issue that /boot/initrd.img appears to be broken after JP-4.4, the initrd.img is too big for usage,
please refer to these discussion thread, Topic 78540, and Topic 191060, for simple fixes to switch from the default MODULES=most to MODULES=dep.

there’s another discussion thread, talking about how to setup a readonly rootfs without an initramfs.

I would expect the disk being mounted in RO mode to cause a new set of problems. Let’s say you have a software that writes a change to the disk and expects that change to be read back again later, e.g. any of the default linux services. OverlayFS will give you the modified file from RAM, while a RO disk will give you the unmodified file… But that also means that OverlayFS will fill up your RAM over time with the changes that it keeps in memory, and is only really recommended if you restart the system regularly, e.g. daily. In such a scenario, your Nano will live in a kind of Groundhog Day world, with a short-term memory of the things that happened during the day, but no recollection of anything prior (also no log files of that, obviously).

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