From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 28 May 2001 16:14:12 +0000 From: "Heinz J. Mauelshagen" Subject: Re: [linux-lvm] Root on LVM and vgscan Message-ID: <20010528161412.B21043@sistina.com> References: <20010528112030.H26710@sistina.com> <200105281244.NAA14609@queeg.britain.agilent.com> Mime-Version: 1.0 In-Reply-To: <200105281244.NAA14609@queeg.britain.agilent.com>; from dick@britain.agilent.com on Mon, May 28, 2001 at 01:44:34PM +0100 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: List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com On Mon, May 28, 2001 at 01:44:34PM +0100, Dick Middleton wrote: > > Thanks for your answers - as usual they provoke more questions... > > > On Fri, May 25, 2001 at 09:28:34AM +0100, Dick Middleton wrote: > > > I have root running on lvm on sw raid partitions on linux 2.2.18. It all > > > works fine. However I have had difficulty during booting after adding new > > > LVs. The symptom is that the initial mounts of LVs fails or the wrong > > > partition is mounted. > > > > > > What happens is that vgscan is run during the initrd phase and so the lvmtab > > > is updated on the ram disk. Once the root file system on the hard disk has > > > been mounted the lvmtab on that comes into use. That has not been updated by > > > vgscan and so does not reflect the changes. > > > > > > Obviously it's possible to run vgscan again (between remounting root rw and > > > checking the other discs) to update the lvmtab but it does beg a few > > > questions. > > > Yes, that's the option (forcing some overhead). > > The other would be to get the actual /etc/lvmtab* from the initial ram disk :-) > > Ah yes, I discovered that it lives in /initrd! Can I assume from this that > it's safe to copy the lvmtab. Is that a good solution? Sure. This has the actual vgscan results *and* causes as little overhead as possible to get it into the real root. > > > > > > > 1) why does mount use the data in lvmtab and not in /proc to find out about > > > active VGs? > > > mount doesn't access /etc/lvmtab* at all. > > Now you've got me. Why/how does mount mount the wrong partition when lvmtab > is out of date if it doesn't access lvmtab? Are /dev// updated by > vgscan as well? It looked to me as if they weren't. Do they need to be copied > from /initrd too? Actually I've been too brief before :-( The device nodes in your real root are the ones created *before* vgscan was called from linuxrc and are likely out of date WRT to the minor numbers they contain. Something like /dev/VGName/LVname 58 1 could be in your real root *but* /dev/VGName/LVname 58 2 could have been updated by the vgscan run in the initial ram disk fs. IOW: you can copy the /etc/lvmtab* files from the initial ram disk *and* run vgmknodes(8) from your real root based startup script *before* the VG is accessed (eg. to mount a fs). > > What should I read to better understand how all this works? > > Dick > _______________________________________________ > linux-lvm mailing list > linux-lvm@sistina.com > http://lists.sistina.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html -- Regards, Heinz -- The LVM Guy -- *** Software bugs are stupid. Nevertheless it needs not so stupid people to solve them *** =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Sistina Software Inc. Senior Consultant/Developer Am Sonnenhang 11 56242 Marienrachdorf Germany Mauelshagen@Sistina.com +49 2626 141200 FAX 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-