From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: [linux-lvm] A way to bypass LVM and extract the raw data off? Message-Id: <20020109152549.Y769@lynx.adilger.int> References: <1010309724.3c381a5ce8cbe@www.snappymail.ca> <1010343969.3c38a0214056f@www.snappymail.ca> <20020106152433.Q12868@lynx.no> <1010359883.3c38de4b3692f@www.snappymail.ca> <1010543196.3c3baa5c40c49@www.snappymail.ca> <20020109023404.GC1096@auctionwatch.com> <1010545378.3c3bb2e2a4dec@www.snappymail.ca> <20020109124025.O769@lynx.adilger.int> <1010612597.3c3cb975632ae@www.snappymail.ca> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1010612597.3c3cb975632ae@www.snappymail.ca>; from ipso@snappymail.ca on Wed, Jan 09, 2002 at 01:43:17PM -0800 Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: Date: Wed Jan 9 16:26:02 2002 List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: IpSo Cc: linux-lvm@sistina.com On Jan 09, 2002 13:43 -0800, IpSo wrote: > Quoting Andreas Dilger : > > On Jan 08, 2002 19:02 -0800, IpSo wrote: > > > Yup! I'm confident everything as far as the reiser filesystem is fine, > > > just LVM is very confused. > > > > > > Device Boot Start End Blocks Id System > > > /dev/hda1 * 1 507 255496+ 82 Linux swap > > > /dev/hda2 508 39813 19810224 5 Extended > > > /dev/hda5 508 4633 2079472+ 83 Linux > > > /dev/hda6 4634 39813 17730688+ 8e Linux LVM > > > > > > Does the LVM information take up the first 2mb or something that I > > > could set the offset as, so it doesn't carry over to the loopback file? > > > > No, it uses a variable amount of space. > > > > What you could do is try > > > > od -Ad -a /dev/hda6 | grep "R e I s E r 2 F s" > > > > and start your dd 65584 bytes before the address at the line this is > > found on (it should align to an even block boundary). > > At the "line", I tried the command and I got about 1000+ lines that seem to > match. I assume I just try from the first line minus 65584 (3276800) like you > said? > > [root@ipso big]# od -Ad -a /dev/hda6 | grep "R e I s E r 2 F s" > 3342384 bs nul soh nul R e I s E r 2 F s nul nul nul > 3383344 eot nul stx nul R e I s E r 2 F s nul nul nul > 3424304 eot nul stx nul R e I s E r 2 F s nul nul nul > 3498032 stx nul stx nul R e I s E r 2 F s nul nul nul > 3547184 eot nul stx nul R e I s E r 2 F s nul nul nul > 3616816 ack nul stx nul R e I s E r 2 F s nul nul nul > 3706928 nl nul stx nul R e I s E r 2 F s nul nul nul > 3825712 nl nul stx nul R e I s E r 2 F s nul nul nul > 3842096 dc4 nul stx nul R e I s E r 2 F s nul nul nul > 3932208 dc4 nul soh nul R e I s E r 2 F s nul nul nul > 3944496 dc4 nul soh nul R e I s E r 2 F s nul nul nul > 3956784 dc4 nul stx nul R e I s E r 2 F s nul nul nul > 4001840 dc4 nul stx nul R e I s E r 2 F s nul nul nul > ... > > dd if=/dev/hda6 bs=512 skip=3276800 of=/big/backup_hda6.bin > > -rw-r--r-- 1 root root 16478502912 Jan 9 12:50 backup_hda6.bin Well, since "od" outputs a _byte_ offset, and "dd" is skipping _sectors_, you need to use: dd if=/dev/hda6 bs=512 skip=6400 of=/big/backup_hda6.bin Granted, all of these superblock copies might be in the journal, so it is hard to tell (with ext2/ext3 there are backup superblocks, but they have numbers assigned to them, so you can still find the proper start of the filesystem. > I also tried: (/dev/hda) > dd if=/dev/hda bs=512 skip=3276800 of=/big/backup_hda6.bin Well, this doesn't make sense, since the offset is relative to the start of /dev/hda6. Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/