Re: SD card, exfat, file mtime wrong

[David Wright <deblis@lionunicorn.co.uk>]

On Wed 08 Dec 2021 at 16:37:25 (+1100), David wrote:
> On Wed, 8 Dec 2021 at 16:16, David Christensen wrote:
> > On 12/7/21 7:28 PM, David wrote:
> > > On Wed, 8 Dec 2021 at 14:07, David Christensen wrote:
> > >> On 12/6/21 6:37 PM, David Christensen wrote:
> 
> > > I might also check this info
> > >    https://unix.stackexchange.com/a/640906
> > > that I mentioned before, just to see if it was relevant. I didn't
> > > look closely.
> 
> > It looks like vfat only.
> 
> I wonder did you note this part? ...
> """
> Seems like the problem resides in the Linux kernel itself, as the
> timezone may (and usually do) differ between the kernel and the
> userspace. time.c file in the kernel/time in the Linux kernel source
> tree holds (and exports) the struct timezone sys_tz, which is then
> used in fs/fat/misc.c in the FAT time <-> UNIX time conventions. The
> tz_minuteswest field of this struct is used to show the difference
> between the current timezone and the UTC, and it is taken into
> consideration if the tz=UTC option is not passed to the mount.vfat
> command.
> """
> Which I do not read as necessarily being "vfat only".
> 
> Because perhaps you are likewise not passing that option when
> mounting exfat, maybe because it does not even have that
> option, per my other links.
> 
> In your situation, I would run the test code given there to
> see if it is relevant, and if there is any difference with the
> older Debian versions that do work.

It's probably worth reading the Release Notes for bullseye, §2.2.8,
and making sure that you're using the appropriate utilities. That
section indicates the main change that has occurred.

If the camera is just a camera, my advice would still be to use UTC.
It's astonishing how complicated using anything else can become, as
/everything/ that touches the filesystem and the image and its
thumbnails etc etc has to get it absolutely right.

Cheers,
David.