[CentOS] CentOS 7 install on one RAID 1 [not-so-SOLVED]

Thu Jan 26 04:29:28 UTC 2017
Rob Kampen <rkampen at kampensonline.com>

On 26/01/17 05:46, Tony Mountifield wrote:
> In article <1485342377.3072.6.camel at biggs.org.uk>,
> Pete Biggs <pete at biggs.org.uk> wrote:
>> On Tue, 2017-01-24 at 17:14 -0500, m.roth at 5-cent.us wrote:
>>> So, it installed happily.
>>> Then wouldn't boot. No problem, I'll bring it up with pxe, then chroot and
>>> grub2-install.
>>> Um, nope. I edited the device map from hd0 and hd1 being the RAID to
>>> /dev/sda and /dev/sdb, then ran grup2-install. It now tells me can't
>>> identify the filesystem on hd0, and can't perform a safety check, and
>>> gives up.
>>> What am I missing? Google is not giving me any answers....
>> Surely, if you are using software RAID, then you should configure that
>> RAID in anaconda, that will then cope with setting up the partitions to
>> allow booting.  Basically it needs a small non-RAID partition to hold
>> /boot on the boot disk.
>> Remember that the boot sequence is generally: BIOS reads MBR and
>> executes it; MBR code reads kernel from /boot and executes it (yes,
>> it's more complicated than that). If the MBR code doesn't know how to
>> read a RAID partition, then it's going to fail, that's why you have a
>> small non-RAID partition to hold /boot.
>> Hardware RAID is different because it interfaces at the BIOS level so
>> the MBR code doesn't need to know how to specifically read it.
> If you are using RAID 1 kernel mirroring, you can do that with /boot too,
> and Grub finds the kernel just fine. I've done it many times:
> 1. Primary partition 1 type FD, size 200M. /dev/sda1 and /dev/sdb1.
I think it wiser to have /boot at 1Gb nowadays.
> 2. Create /dev/md0 as RAID 1 from /dev/sda1 and /dev/sdb1.
> 3. Assign /dev/md0 to /boot, ext3 format (presumably ext4 would work too?)
> 4. Make sure to setup both drives separately in grub.
> Typically I then go on to have /dev/sda2+/dev/sdb2 => /dev/md1 => swap,
> and /dev/sda3+/dev/sdb3 => /dev/md2 => /
> Cheers
> Tony