FreeBSD-10.3-RELEASE-i386-memstick.img installer changes contents of USB flash drive?

David Christensen dpchrist at
Wed Sep 28 19:40:29 UTC 2016

On 09/28/2016 09:58 AM, Anton Yuzhaninov wrote:
> AFIK UFS superblock is updated every time filesystem is mounted, even
> if FS is mounted in read-only mode (please correct me if I wrong).

On 09/28/2016 11:34 AM, Ian Smith wrote:
> We discerned recently that for 10.3, i386 memstick is GPT/EFI and
> amd64 is still MBR/BSD.  Since only the last sector differs, perhaps
> something has updated the secondary GPT during the installation,
> assuming that a GPT image should already include one - or at least,
> the space for one?

Thank you both for the replies.

Either of the two mechanisms (filesystem superblock, spare GPT partition
table) might explain the symptoms.

> Possibly this doesn't matter at all, but it does seem 'untidy' at
> best.

Changing the last block of the image on a USB flash device violates the
"Principle of Least Surprise" -- I expect the installation image to be
"read only"; any change indicates a corrupt image and/or media failure.

> I wonder if a hardware-write-protected GPT memstick would have
> issues?

The last USB flash memory stick I bought with an lock/unlock switch was
a Memorex 128 MB in 2006.  Since then, I've bought SanDisk, and they
lack a switch.  STFW there are a scarce few models with switches.
Here's one that also has secure firmware:

How do I file a bug report against FreeBSD-10.3-RELEASE-i386-memstick.img?


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