[SATLUG] read only usb fs

Borries Demeler demeler at biochem.uthscsa.edu
Sat Sep 10 17:59:44 CDT 2011


> 
> 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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