Can not mount USB device

[doug at fledge.watson.org]

On Wed, 19 Oct 2016, Ian Smith wrote:

> In freebsd-questions Digest, Vol 646, Issue 2, Message: 14
> On Mon, 17 Oct 2016 16:25:36 -0400 (EDT) doug <doug at fledge.watson.org> wrote:
>
> > The system is FreeBSD 10.3-RELEASE-p7 #0. All commands are execured as root.
> >
> > file -s /dev/da0s1
> > /dev/da0s1: DOS/MBR boot sector, code offset 0x58+2, OEM-ID "MSDOS5.0",
> > sectors/cluster 8, reserved sectors 38, Media descriptor 0xf8, sectors/track 63,
> > heads 16, hidden sectors 8192, sectors 831488 (volumes > 32 MB) , FAT (32 bit),
> > sectors/FAT 813, serial number 0x482393a9, unlabeled
> >
> > I ended up with the following attempts
> >
> > mount -t msdosfs -o -m=644 /dev/da0s1 /mnt/
> > 5mount_msdosfs: /dev/da0s1: Permission denied
> >
> > dmesg:
> > (da0:umass-sim0:0:0:0): Error 13, Unretryable error
> > g_vfs_done():da0s1[WRITE(offset=19456, length=4096)]error = 13
> > (da0:umass-sim0:0:0:0): WRITE(10). CDB: 2a 00 00 00 20 26 00 00 08 00
> > (da0:umass-sim0:0:0:0): CAM status: SCSI Status Error
> > (da0:umass-sim0:0:0:0): SCSI status: Check Condition
> > (da0:umass-sim0:0:0:0): SCSI sense: DATA PROTECT asc:27,0 (Write protected)
>
> Looks like it either has a write-protect switch, as some do, or it came
> write protected, ie is designed to be read-only, as apparently some are.
>
> > mount -t msdosfs -o -m=644,-M=644 /dev/da0s1 /mnt/
> > mount_msdosfs: /dev/da0s1: Permission denied
> >
> > dmesg:
> > (da0:umass-sim0:0:0:0): Error 13, Unretryable error
> > g_vfs_done():da0s1[WRITE(offset=19456, length=4096)]error = 13
> >
> > All other variations got the same error (Permission denied)
> >
> > The USB stick is readable in windows 10. I thought it was a data disk it turns
> > out to have 2 install program files one for windows and one for mac.
>
> So try mounting it read-only.  As root, you don't need to mess with the
> permissions either, so just this should work:
>
> # mount -t msdosfs -r /dev/da0s1 /mnt	# alternatively '-o ro'
>
> cheers, Ian

Bingo - thank you, I guess I should have got that out of 'man' but that ship had 
sailed