blockdev --setro não funciona (pelo menos para mim)

Question

Tenho certeza de que não entendi como o blockdev funciona.

Eu montei uma unidade flash e ela foi mapeada para /dev/sdb1 . Então eu digito um terminal (como root):

root# blockdev --setro /dev/sdb1
root# blockdev --report

o relatório foi:

Como você pode ver, o relatório disse que /dev/sdb1 está definido como somente leitura (ro). Mas ainda sou capaz de criar arquivos e pastas no pen drive.

O que eu sinto falta?

    

Answer 1

Isso parece ser um problema com blockdev e os drivers usados para interagir com os HDDs.

excerto - RE: Loopback somente leitura para disco físico

> Another option that I recently found was the 'blockdev' command. You can 
> specify that the blockdev is ro even before mounting.
>
> $ blockdev --report
> $ blockdev --setro /dev/device
>
> But my professor brought up the point - these probably depend on the 
> driver used. Maybe a driver for ntfs totally ignores the ro switch? I 
> don't totally agree that blockdev would be based on the driver, but how do
> you test whether the drive actually is in ro without writing? What if
> it fails?

Além disso, esta seção é relevante:

Well, the filesystem code will (or should) go through the block layer, so using blockdev --setro should be effective. However, partitions don't seem to inherit the read-only flag! In other words, if you have a hard disk /dev/sda with a single partition /dev/sda1, you can do blockdev --setro /dev/sda but if you then do blockdev --getro /dev/sda1 you'll notice that sda1's read-only flag is not set! I haven't verified yet whether sda1 can be written to in those circumstances.

Portanto, partições dadas não parecem herdar as permissões de leitura / gravação que você provavelmente precisará usar mount .

outro trecho

> Then the saving grace - loopback devices. Mount the partition as a file. 
> You don't need to worry about drivers, support, etc.
> To do this use losetup to create a loopback device:
>
> $ losetup -r /dev/loop1 /dev/hda1
>
> This creates a read-only loopback device  pointing to '/dev/hda1'
> Then you can mount the loopback device (read-only if you are paranoid)
>
> $ mount -o ro /dev/loop1 /media/test

> This mounts the loopback device loop1 at '/media/test'. You can then 
> traverse the directory of '/dev/hda1' just like it was mounted.

> According to the PDF document I mentioned above, doing this:
>
> $ mount -o ro,loop /dev/hda1 /media/test