[Klug-general] Solution to media cards mounted read only

[Thomas Edward Groves]

At the risk of being a bloody fool:
you do know that there's a little switch on the side, do you?
Sometimes the obvious isn't.

Tom
----- Original Message -----
From: James Morris <jwm.art.net at gmail.com>
To: Kent Linux User Group - General Topics <kent at mailman.lug.org.uk>
Sent: Saturday, November 19, 2011 1:13 PM
Subject: [Klug-general] Solution to media cards mounted read only


> Hi,
>
> I'm posting this in the event that someone finds it useful. It's one
> of those problems that I've been working around for ages but finally
> had enough of to locate a solution.
>
> I've long thought it was my own fault that SD cards mount read-only,
> that some aspect of system configuration was missing.
>
> However, every so often, they do mount with write access but then time
> passes and they don't. Again I assumed that system configuration had
> changed after updates/distro change etc.
>
> Today I found some claims that read-only mode in Linux is caused by
> file system errors on the SD card. Apparently using the card in MS
> Windows fixes the problem. But that's too inconvenient and not a
> solution I want to use.
>
> The cards I have are not old nor heavily used, so I tried mounting
> them in turn and eventually found one which successfully mounted with
> read/write mode.
>
> Comparing kernel output via dmesg of the different cards revealed they
> had different 'mode sense' values, which seemed to confirm what I read
> about flags in the card's file systems which caused Linux to mount
> them read only.
>
> This brought me to the search terms 'sdhc "mode sense"' which yields
> the solution* which doesn't involve MS Windows.
>
> You need the hdparm utility installed, and also, to know the device
> node. Basically you use hdparm to force Linux to re-read the partition
> table of the card. For instance, on my system:
>
> hdparm -z /dev/sdd
>
>
>
> James
>
> *
http://forums.gentoo.org/viewtopic-p-6367579.html?sid=58a500f3e297c47e843871
e6c67db21f#6367579
>
> PS Some of these cards are min-sd's inserted into a micro-sd adapter.
> The 16gb card had become unmountable in it, the 2gb card was mountable
> read-only... I did hdparm -z /dev/sdd on the 2gb, and now have
> read-write access on it, but also, on the 16gb too!?
>
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