Date: Wed, 28 Sep 2016 12:58:43 -0400 From: Anton Yuzhaninov <citrin+bsd@citrin.ru> To: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: FreeBSD-10.3-RELEASE-i386-memstick.img installer changes contents of USB flash drive? Message-ID: <028307a7-0771-6429-d72f-f85f9530f55d@citrin.ru> In-Reply-To: <56532342-f2d4-377d-605b-2e1b5bfb2160@holgerdanske.com> References: <56532342-f2d4-377d-605b-2e1b5bfb2160@holgerdanske.com>
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On 2016-09-25 23:36, David Christensen wrote:
> # time dd if=/dev/sdc count=1350917 | sha256sum -b
> ab104a30627754bb8d39eeff3c5c5a4a15537d32c749e2b9841b34cb08e17eb0 *-
...
> But after using the USB flash drive to install FreeBSD, the checksum has
> changed:
>
> # dd if=/dev/sdc count=1350917 | sha256sum -b
> bd159b85486322febe992226bbec9c86d96d70dd1e5a8b7c6f0bb9d29eb50df3 *-
> 691669504 bytes (692 MB) copied, 42.989 s, 16.1 MB/s
>
> Therefore, the FreeBSD-10.3-RELEASE-i386-memstick.img installer has
> changed the contents of the USB flash drive.
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).
In struct for superblock I see:
struct fs {
...
u_char fs_fsmnt[MAXMNTLEN]; /* name mounted on */
...
ufs_time_t fs_mtime; /* Last mount or fsck time. */
...
}
If you can mount this USB flash in FreeBSD before and after install you
can use mtree to check that files was not changed:
$ mtree -c -K sha256 -p /mnt/usb-flash > /tmp/mtree1
use USB flash to install FreeBSD
$ mtree -c -K sha256 -p /mnt/usb-flash > /tmp/mtree2
$ diff -u /tmp/mtree[12]
Only commented lines in mtree header should differ.
And see if files was changed.
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