Re: HOWTO: USB boot on 8 GB RPi4 with no SD card

[mlelstv%serpens.de@localhost (Michael van Elst)]

tsprad%talent-free-studios.com@localhost (Ted Spradley) writes:

>I downloaded the arm64.img.gz again, gunzipped it (same checksum), and
>dd'ed it to my USB memstick again, and I still can't mount it on my
>laptop nor on my RaspberryPi 2B, both running NetBSD-9.0_RELEASE.

>"mount_ffs: /dev/dk1 on /mnt: incorrect super block"

Yep. fsck recognizes the filesystem and doesn't report an error,
but mount fails.

The reason is that the image is truncated.

The ffs partition in the current image is 2326528 disk blocks.
The superblock specifies a size of 145792 frags = 2332672 disk blocks.

The mount operation checks access to the last block unless you
mount read-only. So mount -o ro actually works on the truncated
image.

The GPT also reveals where the sizing is mixed up:

    start     size  index  contents
        0        1         MBR
        1        1         Pri GPT header
        2        4         Pri GPT table
        6    32762         Unused
    32768   163840      1  GPT part - EFI System
   196608  2326528      2  GPT part - NetBSD FFSv1/FFSv2
  2523136     6139         Unused
  2529275        4         Sec GPT table
  2529279        1         Sec GPT header

The missing 6144 blocks of the filesystem exist in the image but
are Unused or store the backup GPT.

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."