Analysing differences in images produced with mkimg and makefs

Chris Lamb lamby at
Tue Dec 7 00:45:25 UTC 2021

Fabian Keil wrote:

(Noting the issues you mention with ElectroBSD binaries so will
proceed using FreeBSD memstick images as you suggest.)

> You could download a FreeBSD 12.3 memstick image from
> <>,
> copy it and modify a couple of bytes in the copy and try to
> compare them.

Sure thing. Although instead of modifying a few bytes which might
damage the file beyond sensible comparison I'm just going to compare
two pristine FreeBSD memstick images, specifically:

  $ sha1sum *
  ff3bac56a48161a175ebe340f2d094f864183c33  FreeBSD-12.3-STABLE-amd64-20211125-r371091-mini-memstick.img
  842b252835975d21334f55bc93eb88108f4886e6  FreeBSD-13.0-STABLE-amd64-20211111-7647baa1e8f-248036-mini-memstick.img

However, there seems to be something a little interesting about these
images. Specifically, whilst this works:

  $ virt-list-partitions FreeBSD-12.3-STABLE-amd64-20211125-r371091-mini-memstick.img

... the following does not:

  $ virt-list-filesystems FreeBSD-12.3-STABLE-amd64-20211125-r371091-mini-memstick.img           
  list_filesystems: sfdisk exited with status 1: sfdisk: /dev/sda: partition 5: partition table contains only 4 partitions at /usr/bin/virt-list-filesystems line 166.

I'm using these two tools as diffoscope's filesystem image support
uses libguestfs (the library underlying the virt-* tools).

Any ideas about what is different about these images? Getting them mountable by
guestfs first step as I see it.

Best wishes,

     : :'  :     Chris Lamb
     `. `'`      lamby at 🍥

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