JP Vossen via plug on 28 Jun 2020 13:27:30 -0700


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Re: [PLUG] Fixing /boot/ too small


Well, what I *can* say is that when I fumbled around fixing the problem on my PC last Monday I did `grub-install --boot-directory=/mnt/boot /dev/sda` and the same for sdb. Note that was without a `chroot` but on the disk itself, not any partition or md device. My PC worked.

Then yesterday I did not do that step because I figured `update-grub` was enough yet it did NOT work. I got the same symptom, GRUB totally ignored all the Linux stanzas that DID EXIST in `grub.cfg` and booted right into memtest. When I booted the LiveUSB, did the `chroot` and this time `grub-install /dev/sda` and sdb...it then worked.

Beats the heck out of me.


On 6/28/20 4:16 PM, Keith C. Perry via plug wrote:
I would say this is a case of grub doing what we say and not what we mean...

What we really want is to install grub to the mirror volume (i.e. the thing analogous to the the physical disk).  Seems to me that should work or grub should have the knowledge to know that "oh this is mirror so let me install on all physical copies".  We're not going to be aware of any vg or lv util the system starts to boot and for that to happen, boot bits have to be on the physical drives.  Since I've never seen this documented, I'm assuming what actually happens is that the vg or lv actually would be corrupted.  I also don't think its documented anywhere that boot mirrors need to install grub to each physical disk for things to work properly if a mirror fails.

You're probably right that you don't have to reinstall since the grub.cfg will enable the mirror set during boot.  I've never worked out when exactly this need to be done so I just make it part of my procedure.  When I was running Slackware, I think I only ran LILO when there were kernel changes.

I'm not sure you "missed" anything per se.  There is just a bit of a disconnect between all these components because there has to be.

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Keith C. Perry, MS E.E.
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----- Original Message -----
From: "JP Vossen via plug" <plug@lists.phillylinux.org>
To: "Philadelphia Linux User's Group Discussion List" <plug@lists.phillylinux.org>
Sent: Sunday, June 28, 2020 3:35:22 PM
Subject: Re: [PLUG] Fixing /boot/ too small

On 6/28/20 3:21 PM, Keith C. Perry via plug wrote:
Awesome JP !!

I could have sworn I mentioned that you had to do grub install to both mirror disks for true protection.  That has to be done even when you just use LVM to do your RAID 1.

You probably did and I probably *assumed* that `grub-update` would take
care of it.  Any clue why it does not?  I mean, once you install GRUB
it's installed, right?  So why do I need to reinstall it when I make a
config change?  OK, it's a significant change, perhaps even a
fundamental one...but it's still a config change.  And I never touched
the start of /dev/sda or sdb.

And it's not like the old /boot/ was not on mdadm too, it was.  It's
just that now /boot/ is on root on /dev/md1 instead of just being /boot/
on /dev/md0.  Clearly I seem to be missing something.
Later,
JP
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