Re: Grub2 install with / on lvm

[jeff]

Comments / questions inline below.
 
>-----Original Message-----
>From: "Andrei Borzenkov" <address@hidden>
>Sent: Saturday, February 7, 2015 7:29am
>To: address@hidden
>Cc: address@hidden, address@hidden
>Subject: Re: Grub2 install with / on lvm
>
>
>
>В Wed, 4 Feb 2015 13:57:59 -0800 (PST)
>address@hidden пишет:
>
>> 
>> Greetings -
>> 
>> I have been experimenting with an Linux Mint 17 installation for my desktop 
>> system. This is on a new Dell Precision 3610. After having difficulties 
>> getting the Mint installation to complete (grub2 install failed) with 
>> software RAID (and trying the Intel IMSM fake raid) I finally purchased a 
>> good hardware raid card and installed it in my system (LSI MegaRAID SAS 
>> 9271-8i). Now Mint installs without grub2 install failing during the 
>> installation; however, at first boot I get sent to a grub prompt. After 
>> playing around with the SuperGrub2 Disk I think I have isolated the problem. 
>> Here is a description of my system and what I have found.
>> 
>> 1. RAID 1 of two 3-TB drives (entire drives, not partitions)
>> 2. Single drive recognized by BIOS and Mint installer as /dev/sda
>> 3. Created partitions and lvm logical volumes in GParted and command line 
>> prior to install
>> /dev/sda1 500MB /boot/efi fat32
>> /dev/sda2 500MB /boot fat32
>
>symbolic links are commonly used in /boot so fat32 is probably not the
best idea.

Ok, I learned something new here.  What would be a better choice for the 
filesystem for /boot.  I am using xfs for everything else.

>
>> /dev/sda3 volume group vg_jab (left 100MB unallocated at end)
>> lv_mintroot 8GB /
>> lv_mintvar 4GB /var
>> lv_mintswap 2GB [swap]
>> lv_minthome 80GB /home
>> lv_mintgis 1000GB /gis
>> 4. I will be installing Windows 7 as a VM (using KVM) later in an additional 
>> lv.
>> 5. Interestingly df-h does not show /dev/sda2, and ldblk does not show a 
>> mount point for /dev/sda2
>> 6. Grub settings point to hd0, gpt1. In grub I see a message of failure 
>> reading sector ???? from hd1
>> 
>
>You said you have single disk, so there is no surprised grub cannot
read from hd1 - it should not exist. Where it comes from in grub
configuration?

That I don't know, and I don't have enough knowledge right now to know where 
specifically to look.  I would like to see what configuration file is 
referencing that to get a better understanding of what is going on.  Can you 
point me to where I might look for that?

>
>> In SuperGrub2 Disk a linux boot image is not present when selecting 
>> Everything. If I select Everything+ a boot image appears. Individually going 
>> through the options in Extra Grub2 functionality, I get a linux boot image 
>> to appear if all I do is enable grub2's LVM support. I booted from this 
>> installed image and tried running grub-install. A reboot after that did not 
>> resolve the issue. It appears that my grub installation does not have the 
>> support for lvm, and it appears that my root partition being on lvm is 
>> likely the problem, as somewhere along this path I saw grub referencing the 
>> UUID that is my lv_mintroot.
>
>You do not say how you install bootloader. If you are using
distribution specific scripts you may have better luck on corresponding
list.
>
>In general "grub-install /dev/sda" should figure out what drivers are
needed to access /boot/grub and include them in image. If /boot/grub is
on LVM, grub should include drivers for it in image. It is impossible
to say what is wrong without knowing exact procedure how grub was
installed.
>

Grub was installed using the standard OS installation in Linux Mint 17.  I 
haven't had much luck getting good knowledgable detailed answers there; more 
speculation and hypotheses.  It is good to know that grub install would 
normally include the LVM driver, so it is possible that Mint installation is 
not recognizing that I am using LVM.  Is there a grub config file that would 
identify the drivers that are pulled in, and I would be able to see if the 
driver for LVM is included.  I don't want to get into hand editing grub 
configuration files to get my system running.  I would prefer to have it 
automatically the right way, I just want to understand what it did in case it 
helps find or fix a bug in the Mint installation.

After I booted the system from the SuperGrub2 disk, I did run grub-install 
/dev/sda just to see what would happen (since I was considering re-installing 
anyway).  If I recall it ran without error, but still wouldn't boot and had the 
same reference to hd1.

>> 
>> I am looking for advice on what might be the best approach to take now. I 
>> have no problems if that means re-doing my partitions and taking / off of 
>> lvm. I am just not sure that is the only problem, or the entire solution, or 
>> even the best solution overall. I would like to hear what my options might 
>> be before going through the reinstallation.
>> 
>> Please cc me directly, as I am only subscribed to the daily digest. Thanks.
>> 
>> Jeff
>>