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

[James Morris]

On 20 November 2011 06:34, Thomas Edward Groves <teg451013 at freeuk.com> wrote:
> At the risk of being a bloody fool:
> you do know that there's a little switch on the side, do you?

Yes.

Just curious, but have users of distributions where automounting is
setup out the box experienced these problems?

James.


> 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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>> Kent at mailman.lug.org.uk
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>
>
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