[ubuntu-uk] Missing write-protect tab on Secure Digital SD card causing read-only?

Andrew Oakley Andrew.Oakley at hesa.ac.uk
Wed May 20 11:39:31 BST 2009

Matthew Daubney wrote:
> On Wed, 2009-05-20 at 10:06 +0100, Andrew Oakley wrote:
> > I understand that the write-protect tab on SD cards is optional:
> > However, when I use an SD card without a tab (no tab at all) on my
> > Linux Ubuntu 8.04 LTS server, it mounts it as read-only (ro) and
> > absolutely refuses to mount read-write (rw) even if the 
> When you insert it into your ubuntu machine can you produce a dmesg
> output? I've had one or two that wouldn't mount rw because of
> inconsistances in the filesystem. They mounted fine after an fsck.

Thanks. I tried the fsck, even after unmounting it failed as the device
was considered read-only. Ditto unmounting then attempting to reformat
on the Linux box, fails as read-only. I even reformated it cleanly on
the MS-Windows machine. Still Linux box complains read-only.

Therefore I'm reasonably sure that it is the notch or the lack of tab
which is causing the problem. The question is, which machine is correct;
should an SD card which has a notch, but has no tab, be considered
read-only? I'm wondering whether the card is faulty by design, since it
has a notch but no tab (ie. if the card has a notch, it should have a
tab). Or whether my card reader is faulty by design for insisting on a
tab that need not be there.

Andrew Oakley
Head of Software Development
Higher Education Statistics Agency (HESA)
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