[TriLUG] Problem with LVM

[T. Bryan]

On Sunday 04 June 2006 23:58, Brian McCullough wrote:
> On Sun, Jun 04, 2006 at 03:55:49PM -0400, T. Bryan wrote:
> > I tried rebuilding everything.  My only remaining problem is that things
> > don't quite work on boot.  Details are below, but after I boot and login,
> > the quickest way to get everything working is to
> > /etc/init.d/lvm stop
> > mdadm -S /dev/md0
> > mdadm -As /dev/md0
> > /etc/init.d/lvm start
>
> I'm sure that David is quite capable of contributing some words of
> wisdom, here.  I'm sure that I'm missing something obvious.

Thanks.  

> This is starting to smell suspiciously like a faulty initrd file.  As
> you say, you have MD active during the dmesg time, but no sign of LVM
> activity.  Although you aren't using LVM as root, it might be a good
> idea to make sure that you have LVM available "in the kernel" at
> boot time.

Good idea.  My old LVM set up died when I upgraded my kernel to 2.6, and I've 
just been using the stock Debian kernel.  Sounds like it's time to build a 
kernel.  I'll probably give that a try first to rule that out.

> Incidentally, side note time -- do you have both MD component partitions
> ( hde1 and hdg1, if I remember correctly ) marked as type "fd",
> Linux Automatic Raid?  ( not really an issue, since you show that the MD
> part of things is working )

Yes.

> Also, we haven't discussed this -- we talked about filtering out the
> components of the md array, but did we talk about filtering IN the md0
> device itself?  Same part of the lvm.conf file, but using the "a" flag
> instead of the "r'.

No.  I can try that, too.  (Not able to at the moment...broken dist-upgrade.)

> OK, I think that we have established the following, but bear with me.
>
> Use fdisk to create two, identically-sized, type "fd" partitions, hde1
> and hdg1.
> Use mdadm to create md0 from those two partitions, in RAID 1
> configuration.
> Use pvcreate on md0.
> Use vgcreate, using md0.
> Use lvcreate, using new VG.
> Format the new LV.
> Modify fstab appropriately.

Yes.  

> At this point you should be able to mount and use the LV as a normal
> part of your filesystem.

And I can...after the system has booted.  I just shouldn't have to do it by 
hand.

> > I have the following symlinks in /etc/rc2.d/
> > S25mdadm
> > S25mdadm-raid
> > S26lvm
>
> Silly question, but S26lvm _does_ point at a reasonable location,
> doesn't it?

Yes.  I was actually using /etc/rc2.d/S26lvm stop and start to mess with LVM 
after boot.  Just to verify that the symlink and linked script were acting 
correctly.

> > Now, if I run lvmdiskscan, it sees the LVM physical volume
> >   /dev/md0  [      111.79 GB] LVM physical volume
>
> But you haven't run vgscan yet.  That is essential for any of the
> funtionality that you are looking for.  vgscan followed by vgchange,
> which is what your restart of /etc/init.d/lvm is doing.

Ah, okay.

> For some reason, this looks as if MD is not actually starting properly
> at boot time -- weird.

At some point it is.  When the system finishes booting, /dev/md0 has been 
started (assembled and status shown in /proc/mdstat).  

> > # /etc/rc2.d/S26lvm start
> > Setting up LVM Volume Groups...
> >   Reading all physical volumes.  This may take a while...
> >   Found volume group "localvg" using metadata type lvm2
> >   /dev/localvg: opendir failed: No such file or directory
> >   1 logical volume(s) in volume group "localvg" now active
>
> I don't like that error message.  It seems to be out of order.

Okay.  I'm planning to ignore it for now until I figure out whether any of the 
other things fix my problem.  Maybe then I'll return to this one to see 
whether the error message changes.

> I agree that something is broken.  I just think that I'm missing
> something vital in what you are saying, or not saying.

Thanks for all of your help.   It's quite frustrating since the LVM on RAID 1 
is *almost* working.  Not well enough that I feel safe trusting it or using 
it.  Not broken enough that I can just look on Google and find an error 
message.  

I haven't done much with my systems in a while.  I forgot how much "fun" Linux 
could be.  :-/

---Tom