Re: loopback on block device

[Lei Yang <lya755@ece.northwestern.edu>]

Why /dev/ram0 is a file? Can you get into more details? For example, if 
I want to do some system level programming and write to a /dev/ram0, how 
do I do it?

Thanks very much for your reply!

Lei

linux-os wrote:

> On Wed, 27 Oct 2004, Lei Yang wrote:
>
>> Hello,
>>
>> Here is a question for loopback device. As far as I understand,  the 
>> loopback device is used to mount files as if they were block devices.
>>
>> Then Why I could do "losetup -e XOR /dev/loop0 /dev/ram0" ? Notice 
>> that ram0 is not mounted anywhere and does not have a filesystem on 
>> it. I've tried that command and there seems to be no error. I got 
>> confused and looked into loop.c, it seems to me that a loopback 
>> device should be associated with a "backing file", why would it work 
>> on a block device anyway?
>>
>> I'd appreciate your comments greatly!
>>
>> TIA,
>> Lei
>>
>
> `man losetup`
> You just set up the loop device to enable encryption on
> /dev/ram0. /dev/ram0 is a "file". It's a special-file,
> but a file nevertheless. It can contain a file-system,
> therefore act as a RAM disk, but it doesn't have to.
>
> In principle, you could make an encrypted file-system
> in which you couldn't even know what kind of file-
> system it was, without an encryption key.
>
>
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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