exfat on SD card getting mounted read-only

[jd1008]

On 08/26/2014 09:05 PM, Chris Murphy wrote:
> Four observations:
>
> 1. The fsck.exfat command worked. So obviously the mkfs command and kernel aren't seeing the wrong state of the card's physical lock switch. It sounds like a weird bug that it then can't be mounted. Maybe try an explicit mount -t without -o rw. I'd think if it's a bug it'd have been found about an hour later though, pretty significant bug if it's a bug.
# mount -t exfat /dev/mmcblk0p1 /mmcblk0p1
FUSE exfat 1.0.1
WARN: `/dev/mmcblk0p1' is write-protected, mounting read-only.


>
>
> 2.
>
> Aug 25 20:24:27 localhost.localdomain kernel: mmc0: new ultra high speed SDR50 SDHC card at address 0001
>
> SDHC cards are supposed to be formatted FAT32. And SDXC is supposed to be formatted exFAT. That's per the SD Card specs anyway, which is how any camera supporting these types of cards should work.

I had deliberately formatted it as exfat in windows because I was 
loaning it to a friend so he
could fill it for me with files on his apple laptop, with such 
incredibly long file names, that vfat
could not accommodate them, and that caused some files in which the 
first n bytes of the name
were the same, so file 2 for example over-wrote file1.
Thus formatting it as exfat solved that problem and I was able to 
receive those files.

>
>
> 3.
>
> Last, and actually most important, practically obsoleting the above two observations: this card is being used in a camera? The camera must be used to format it. That's what the camera manufacturer and the SD card manufacturer will tell you. The interoperability is *so bad* with SD cards, that they will both tell you that corruption and even camera malfunction is expected if you don't format the card in-camera.
>
> Further, it's well understood by pros and the amateur (the classic connotation of the word implies someone more serious about their interest than even a pro) that the camera image delete option shouldn't be used. Take your shots, fill up the card or get to a good break point to swap cards. When sucking the images off the card with a computer, suck all of them off, back them up, then go through and throw away the junk photos you don't want. Reformat the card in the camera.
Nop! It has never seen a camera :)

>
>
> 4.
>
> Best quote about SD Cards ever: "You aren't storing your data, you're storing a probabilistic approximation of your data."
> https://www.youtube.com/watch?v=CPEzLNh5YIo
> Quote is somewhere around 3m30s; including the point that flash memory is unreliable, and lots of other cool observations. I don't know why these things are called secure digital (SD) after watching this.
Good observation. They say that nand flash has a longer life span as it 
can handle higher
number of writes per block before reaching 50/50 probability :)
As far as "secure" ,  I can say with a great degree of certitude that 
when it comes to
computer data, nothing is secure nor private if you are on the internet, 
regardless of which OS you use.
Even if you use cyphered email (between individuals that share each 
other's publik keys).
In fact, publikly available sypher systems are so readily breakable by 
the nsa, it's a joke
to believe that "encyphering data with freely available cypher systems 
and then xmitting
them over the internet" is secure. After all, if it were not so, these 
cypher systems would
not be freely publicly available.