On Fri, 2007-01-05 at 19:04 -0500, Paul wrote: > On Thu, January 4, 2007 11:40 pm, Alvin Chang wrote: > > On 05/01/07, Aleksandar Milivojevic <alex@xxxxxx> wrote: > >> I've used it, and it works correctly (and it is available in CentOS > >> 4.4). It shrinks file system as it should. The only things Paul should > >> be careful is to first shrink file system, than logical volume and to > >> correctly calculate file system size and by how many extents he can > >> shrink logical volume. If he shrinks logical volume too much, he might > >> end up loosing data. Running fsck in non-destructive mode (fsck -N) > >> and/or attempting to mount file system read-only after he shrinks > >> logical volume might be a good idea to test all is OK. > > A little technique you can use is: > > 1. shrink the file system to the size slightly less than what you really > > want > > 2. reduce LV to the size that is what you really want > > 3. expand the file system to the size of the LV (usually the resize > > program can be told to expand the file system to maximum available > > space automatically on the LV.) > > You guys are great! Thanks. It was a breeze! I really have fun learning > more and more. I feel like an LVM expert now. Here's the steps I took: > > First my lv was like 38G, and I wanted to make it about 32G in the end. I > know that should be way more than enough. I also did a dd to an image > file on a secondary drive for a precaution (always have a failsafe > recovery!) > > 1. booted up on CentOS 4.4 Live CD. -When I booted up on it, I told it > to boot nonet to not bring up the interfaces, but it did anyhow. I did a > "ifconfig eht0 down" to do a shut on it. Anyhow, out of all the LiveCD's > I have tried, I do like the Centos the best! > > 2. e2fsck -fv /dev/VolGroup00/LogVol00 > > 3. resize2fs -p /dev/VolGroup00/LogVol00 30G > > 4. lvresize -L 32G /dev/VolGroup00/LogVol00 > > 5. resize2fs -p /dev/VolGroup00/LogVol00 (size defaults to lv size) > > Now I have my free PV space! > > # pvdisplay > --- Physical volume --- > PV Name /dev/hda2 > VG Name VolGroup00 > PV Size 38.22 GB / not usable 0 > Allocatable yes > PE Size (KByte) 32768 > Total PE 1223 > Free PE 143 > Allocated PE 1080 > PV UUID cQCke5-zi9o-xhOW-HlR5-M46g-VbHC-99Csch > > Now I am on to learning how to do a full backup with snapshots! > Good job ... first thing to understand (at least as I understand it :P) is that you will only be able to create a snapshot that is 6GB or smaller. So, as long as the used space on the LVs you take snapshots of are < 6GB will be OK, otherwise you will have problems. My understanding is that you need free space that is going to be at least as large as the "used space" on the "LARGEST" LV that you are going to create a snapshot for. (At least that is how I currently setup my VGs and LVs where snapshots are involved).
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