Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262548AbUJ0TuD (ORCPT ); Wed, 27 Oct 2004 15:50:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262559AbUJ0Tsb (ORCPT ); Wed, 27 Oct 2004 15:48:31 -0400 Received: from delta.ece.northwestern.edu ([129.105.5.125]:508 "EHLO delta.ece.northwestern.edu") by vger.kernel.org with ESMTP id S262656AbUJ0TlR (ORCPT ); Wed, 27 Oct 2004 15:41:17 -0400 Message-ID: <417FFA38.8000602@ece.northwestern.edu> Date: Wed, 27 Oct 2004 14:42:48 -0500 From: Lei Yang User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.2) Gecko/20040921 X-Accept-Language: en-us, en MIME-Version: 1.0 To: linux-os@analogic.com Cc: linux-kernel@vger.kernel.org Subject: Re: loopback on block device References: <417FE703.3070608@ece.northwestern.edu> In-Reply-To: X-Enigmail-Version: 0.76.8.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 55 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). > Notice : All mail here is now cached and reviewed by John Ashcroft. > 98.36% of all statistics are fiction. > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/