Date: Thu, 21 Jan 2016 16:31:54 +0100
From: Dieter Bloms <dieter@bloms.de>
To: Natanael Copa <ncopa@alpinelinux.org>
Cc: alpine-user@lists.alpinelinux.org
Subject: Re: [alpine-user] alpinelinux 3.3.1 can not boot, when root is on
 lvm, which is on raid1
Message-ID: <20160121153154.GA3679@bloms.de>
References: <20160108205634.GA6702@bloms.de>
 <20160111085919.45eaa3cc@ncopa-desktop.alpinelinux.org>
 <20160111110233.3a20396d@ncopa-desktop.alpinelinux.org>
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In-Reply-To: <20160111110233.3a20396d@ncopa-desktop.alpinelinux.org>
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Hello Natanael,

On Mon, Jan 11, Natanael Copa wrote:

> On Mon, 11 Jan 2016 08:59:19 +0100
> Natanael Copa <ncopa@alpinelinux.org> wrote:
> 
> > On Fri, 8 Jan 2016 21:56:34 +0100
> > Dieter Bloms <alpinelinux.org@bloms.de> wrote:
> > 
> > > Hi,
> > > 
> > > I installed alpinelinux 3.3.1 with manual disc mode.
> > > My root is a logical volume in a volume group on a raid1 system.
> > > During boot the raid is activated, but the logical volumes are not.
> > > So I have to activate it manually and mount it to /sysroot.
> > > After that I can boot into alpinelinux.
> > > 
> > > Is it a known problem, that lvm on a raid is not activated in the
> > > initramfs during boot ?  
> > 
> > It is a known problem. I have the same on my workstation. Sometimes it
> > works and sometimes it fails so I think it is a timing issue.
> > 
> > Today I looked at it a bit and it seems that /sbin/lvm is never
> > executed from initramfs. It means that the nlplug-findfs times out
> > before it gets the hotplug event for mdadm devices.
> > 
> > I think we have a few options for fixing it:
> > 
> > 1) when mdadm is run, make it wait til all mdadm devices are run before
> >    exit. I don't know if this is possible, but nlplug-finds will not
> >    exit til all forked children has exited. This means that mdadm
> >    executes, initalizes the raid devices, and exits long before the
> >    kernel generates the uevent for the raid device. If we could make
> >    mdadm not exit til the uevent is generated, then we should be fine.
> >    I don't know if there is any option for that. (probably not)
> > 
> > 2) When mdadm is started, increase the default nlplug-findfs timeout
> >    (250ms) so kernel gets enough time to generate the raid device
> >    uevent before nlplug-findfs times out. We could increase it with 1
> >    sec for example? The problem is that I don't know what is a good
> >    value since it may depend on the hardware. It will also make boot
> >    slower when you boot to tmpfs root but does not have any apkovl. I
> >    doubt there will ever exist any such setup so the slowdown here is
> >    acceptable.
> > 
> > 3) When boot option `root=...` is specified, increase the default
> >    nlplug-findfs timeout (250ms) to something significantly longer.
> >    Maybe 2 seconds? 5 seconds? If we actually timeout, it means that we
> >    will failed to find the rootfs and the boot will fail. So it makes
> >    sense to increase the timeout for making it not give up that fast.
> 
> I tested this. it didnt help. must be mdadm that mdadm delete/recreate
> the /dev/md* device node so that when the uevent trigger happens,
> the /dev/md* device node temporarily does not exist.
> 
> I think we might need block event handling while mdadm executes. We do
> the same for cryptsetup.

did you have any success on this topic ?

-- 
Regards

  Dieter

--
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