just because unix lets you do something like this, doesn't mean it's either correct or sensible. if you want to do online backup like this PROPERLY, look at <br>lvm2, which can do hot backup using snapshot files..<br><br>okay,,, dd while mounted is bad, and I'd rather you not post it here in case<br>people on this list actually take that as good advice, which it isn't.<br><br>unmount, or use a logical volume manager...end of story.<br><br><br><br><b><i>Robert McWilliam <rmcw@allmail.net></i></b> wrote:<blockquote class="replbq" style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"> On Sun, 24 Feb 2008 23:39:58 +0000, "Andrew Clayton"<br><andrew@digital-domain.net> said:<br>> On Sun, 24 Feb 2008 22:55:52 +0000 (GMT), Lee Hughes wrote:<br>> <br>> > you cant image a filesystem while it's mounted.<br>> > <br>> > either unmount it, or boot from a live disc, and do what you will to<br>> > it from there!<br>>
> <br>> <br>> Works fine on a mounted fs.<br><br>Yes, being mounted doesn't actually cause problems, but being in use<br>will. If the partition you are imaging changes while you are taking the<br>image then you will get a corrupt image. dd basically copies data from a<br>source file to a destination file in chunks, starting at the beginning<br>and working its way through. Changes to a file system have to happen in<br>a couple of places to happen properly, e.g. to create a file you have to<br>put the data somewhere on the disk and update the file table to say<br>where the file is and how big it is and possibly some other stuff. If<br>that happens while dd is taking an image of the file system then the<br>image might only get some of the changes as the others are to areas<br>where dd has already made a copy of the old data. <br><br>To the OP: You'll want to ensure the file system isn't in use<br>(unmounting is the easiest way to be sure) and then run something
along<br>the lines of:<br><br>dd if=/dev/<partition to="" image=""> of=/path/to/put/image<br><br>Robert<br>________________________________________________________<br>Robert McWilliam rmcw@allmail.net www.ormiret.com<br><br>Everything should be made as simple as possible - but no simpler.<br> -- Albert Einstein<br><br><br>_______________________________________________<br>dundee GNU/Linux Users Group mailing list<br>dundee@lists.lug.org.uk http://dundee.lug.org.uk<br>https://mailman.lug.org.uk/mailman/listinfo/dundee<br>Chat on IRC, #tlug on dundee.lug.org.uk<br></partition></andrew@digital-domain.net></blockquote><br><p> 
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