write-protected usb flash drive
freebsd at qeng-ho.org
Sat May 24 15:44:44 UTC 2014
On 24/05/2014 15:22, Gary Aitken wrote:
> On 05/24/14 00:01, Polytropon wrote:
>> On Fri, 23 May 2014 18:26:44 -0600, Gary Aitken wrote:
>>> I'm having trouble locating what I want --
>>> a physically write-protected flash drive.
>>> My searches so far have come up empty.
>>> Thought someone here would know of one if it exists.
>>> I don't want or need additional encryption gimicks on it.
>>> Anyone know of one? 32G or larger
>> I have been using something similar, even though it's not _exactly_
>> what you're asking for. My "solution" (haha): Get a SD card with
>> the required capacity and initialize it as intended. Then use the
>> write protection slider. The card is now write protected. Then get
>> a USB card drive (usually in the shape of a regular USB stick, for
>> example a USK SD/MMC/MS-MMC USB 2.0 card drive) and put the card in.
>> Now you have a write-protected USB drive. :-)
>> There are two advantages:
>> a) In case of media failure, just replace the SD card.
>> b) In case of reader failure, just replace the drive.
>> Additional fun: If you use a SD->µSD adapter, you can also use a
>> micro-SD card. The adapter then provides the write protection slider.
>> The mentioned advantages still apply. :-)
> I like this option better than the Kanguru one,
> mostly because the kanguru drives seem to not be very robust;
> lots of failures reported.
> I don't see why it wouldn't work, but have you tried formatting /
> initializing SD cards from the USB adapter instead of a device like a
Wearing my paranoid sysadmin hat: given that the write protect switch on
SD cards is purely advisory, it would be a good idea to check that the
SD to USB adapter actually honours the advice. I.e. try to write to it
with write protect on.
OK, thought I'd better try my own advice rather than just handing it
out. I put a microSD card out of an old phone into a SanDisk mSD -> SD
adapter and plugged that into my SanDisk SD -> USB adapter, mounted it
(FAT32 file system already on it) and wrote a file to it. Worked as
you'd expect. I then unmounted and unplugged it, flipped the write
protect switch and tried to remount. Result was
mount_msdosfs: /dev/da5s1: Input/output error
Mounting it read-only was fine. So, the write protect is honoured by at
least some SD -> USB adapters. Looks like Polytropn's idea is the way to
go if you want write protectable USB flash drives. The one I've got is a
SanDisk MicroMate Reader, it's USB 2.0 and can handle cards up to 32GB,
so it's just on the edge of what you need. I'd guess there's probably a
USB 3.0 version around by now.
As for formatting SD cards via a USB adapter, I've done that quite
often. So far I've written disk images using dd (for RPi), used
newfs_msdos for both FAT16 and FAT32 and plain newfs for UFS2
filesystems, all without problem.
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