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Re: Write protect access on USB port [WORKS]

Pascal Hambourg <pascal <at> plouf.fr.eu.org> writes:

> Amit a écrit :
> > Pascal Hambourg <pascal <at> plouf.fr.eu.org> writes:
> > 
> >> That's because the filesystem is on a partition, not on the whole disk,
> >> an the partition block device is still read-write.
> >> The read-only flag must be set on the disk and all its partitions. I
> >> guess udev can do this.
> > 
> > I did this for the block device and the partitions as well.
> Are you sure ?
> I set the partition read-only too. When I mounted the ext4 filesystem on
> it, mount detected the flag and mounted the volume read-only. Then I
> unmounted the volume. The md5sum remained the same at each step.

Thanks for checking your set up.

After reading your mail and seeing that it works for you, it got me
looking at my set up. I am using Linux 3.6.0 from upstream so I reverted
back to current debian wheezy 3.2.x and it worked! So I dug deeper and
found out that 3.6.0 and 3.6.1 had the behavior I described with the
wrong checksums. Kernel 3.6.2 has a bunch of ext4 patches that fixes the
issue (although not sure which patch exactly).

So this solution is good enough for now. Although, I would like to note
that doing an sg_dd (even with readonly flag set) still allows you to
write to the drive.

Thanks for all your help!

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