[SATLUG] read only usb fs

mark mark at kandm-solutions.com
Sat Sep 10 18:22:14 CDT 2011


huh I didn't even think about that. I have a card reader (targus) that
works perfectly fine on two of our machines and is completely unusable
on two others. Goes to show the lack of adherence to or existence of
functional standards in these cards readers.

On Sat, 2011-09-10 at 17:59 -0500, Borries Demeler wrote:
> > 
> > I would do a back up and try dd
> > 
> > as root or with sudo (try both tab positions)
> > dd if=/dev/zero bs=1k of=/dev/sdb
> > 
> > if dd can't write to it I'd scrap it
> 
> Thanks for the help, I tried this and it didn't help.
> But I noticed that my laptop has an internal card reader and
> I tried that - and here the card is writable - so it was the 
> reader I was using that only allowed reading. I have never
> seen such a thing, and there is no switch on the reader that
> would allow me to change this to r/w. I guess I'll keep the
> card and ditch the reader.
> 
> -b.
> > 
> > On Sat, 2011-09-10 at 17:17 -0500, Borries Demeler wrote:
> > > > 
> > > > sometimes vfat partitions will get automounted with defaults. By default
> > > > vfat has a mask that makes it read only. if this is the case you need to
> > > > mount it with the option umask=0000.
> > > > mount -t vfat /dev/??? /mount/point -o umask=0000
> > > > 
> > > > after that you should be able to write to it
> > > 
> > > No go:
> > > 
> > > mount -t vfat /dev/sdb1 /mnt -o umask=0000
> > > mount: block device /dev/sdb1 is write-protected, mounting read-only
> > > 
> > > It doesn't matter which position the read protection tab is in, it
> > > will not change the result.
> > > 
> > > Trying to force r/w doesn't work either:
> > > 
> > > mount  -rw /dev/sdb1 /mnt -o umask=0000
> > > mount: block device /dev/sdb1 is write-protected but explicit `-w' flag given
> > > 
> > > stumped...
> > > 
> > > -b.
> > > > 
> > > > On Sat, 2011-09-10 at 16:08 -0500, Borries Demeler wrote:
> > > > > When I try to mount/fdisk or otherwise write to 4 GB SD flash memory
> > > > > from my Canon camera I get an error message that the USB drive 
> > > > > cannot be written to or the partition table cannot be changed.
> > > > > 
> > > > > There is a "lock" tab on the SD card, but neither position makes
> > > > > a difference. I suspect the Canon camera writes some sort of
> > > > > protection onto this card, so I am wondering how I can circumvent
> > > > > this write protection.
> > > > > 
> > > > > It looks like a generic brand of SD card that came with the 
> > > > > camera.
> > > > > 
> > > > > Any ideas on how to make this writable?
> > > > > 
> > > > > -Borries
> > > > 
> > > > -- 
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