On a remote Ubuntu server, I performed a series of upgrades/changes to go from a desktop-install Ubuntu 10.10 Maverick to a server-install of 12.04 LTS Precise
This all went well except a few hiccups I got around, all the while without physical access -so far-. The next goal is to create a XEN server using LVM as backend storage. The system didn't have LVM on it, which I added once I got to 12.04 LTS. I know how to create a XEN machine of it remotely, done it before. But I have an issue trying to boot into the new configuration.
The original person that installed this box didn't pay attention to the partitioning; the machine was used as a server but installed as desktop (this I fixed), but left me with this kind of partitioning scheme:
Disk /dev/sda: 500.0 GB, 499999834112 bytes
...
Device Boot Start End Blocks Id System
/dev/sda1 * 1 58558 470361088 83 Linux
/dev/sda2 58558 60789 17916929 5 Extended
/dev/sda5 58558 60789 17916928 82 Linux swap / Solaris
So I took the huge 17G swap partition and reorganised it a bit into a fresh boot (now /dev/sda2), a small swap partition(/dev/sda3) and a new root (lvs). I got the diskusage down to about 3GB which is small enough and I copied that to a new root, which I created under LVM.
Currently we have
Device Boot Start End Blocks Id System
/dev/sda1 2048 940724223 470361088 83 Linux
/dev/sda2 * 940724224 941748223 512000 83 Linux
/dev/sda3 941748224 943845375 1048576 82 Linux swap / Solaris
/dev/sda4 943845376 976562175 16358400 8e Linux LVM
/dev/sda1 is the old boot partition and I want the machine to boot from /dev/sda2. The difference now is that I now want a separate /boot and / partition. The root partition is known under LVM as :
# lvscan
ACTIVE '/dev/server20/root' [10.00 GiB] inherit
The ultimate goal is that I want to bring /dev/sda1 under LVM control, but I have to boot the system in a way that it's not used. From there on, LVM will work.
In addition to the whole filesystem changes above, I did:
created logical volume:
pvcreate /dev/sda4
vgcreate server20 /dev/sda4
lvcreate -L 10G -n root server20
mkfs.ext4 /dev/server20/root
mounted it:
mount /dev/server20/root /mnt/root/
mount /dev/sda2 /mnt/root/boot/
(cd / ; find . -xdev -print0 | rsync -xavz . /mnt/root/)
for i in /dev /run /dev/pts /proc /sys; do sudo mount -B $i /mnt/root$i; done
update grub:
chroot /mnt/root
echo "dm-mod" >> /etc/initramfs-tools/modules
echo "dm-mod" >> /etc/modules
grub-mkconfig (verified config file visually)
update-grub (no errors/warnings)
Reviewed the created /boot/grub/grub.cfg I see most looks correct, especially stuff like:
insmod lvm
...
set root='(server20-root)'
search --no-floppy --fs-uuid --set=root 0bb92c24-8c02-4fa3-8f75-970076261b2f
...
menuentry 'Ubuntu, with Linux 3.2.0-38-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root='(hd0,msdos2)'
search --no-floppy --fs-uuid --set=root 891b3eaa-fb43-4a42-9789-a91c2a5ffb13
linux /vmlinuz-3.2.0-38-generic root=/dev/mapper/server20-root ro quiet
initrd /initrd.img-3.2.0-38-generic
}
...
Then, checking blkid's:
/dev/sda2: UUID="891b3eaa-fb43-4a42-9789-a91c2a5ffb13" SEC_TYPE="ext2" TYPE="ext3"
/dev/sda4: UUID="IyDrfU-TOYT-rFXO-JknG-rwEK-Sm2A-mfKcIe" TYPE="LVM2_member"
/dev/mapper/server20-root: UUID="0bb92c24-8c02-4fa3-8f75-970076261b2f" TYPE="ext4"
/dev/sda1: UUID="888c061a-1d51-4516-aced-4bb21042d2f4" TYPE="ext4"
/dev/sda3: UUID="19efc041-eccd-42c9-94aa-5b6c88ffd5bb" TYPE="swap"
So, I understand from this is: my boot partition will be msdos2, that would be /dev/sda2 . Also referenced in the search line by uuid, even though it says root, I compared it to other installs and that is meant as the boot uuid (correct assumption?) in case of a split root/boot.
I really assumed this would work to reboot using the additional disk layout, but it didn't. I set both /dev/sda1 and /dev/sda2 bootable flag active using fdisk. It booted the same old way as before, without a hiccup luckily.
My deeper questions are probably sparked in misunderstanding using chroot + update-grub. I actually am not sure what I need to do on the root/boot /dev/sda1 . Do I have to copy the grub.cfg from the chrooted version to the /boot subdir or not ?
Steps I took after the reboot now
switched off bootable flag on /dev/sda1
remounted everything again and performed all steps again plus an additional
grub-install /dev/sda (from the chroot)
Will this be enough to disregard /dev/sda1 ? I read about everything on grub I could find but I fail to get answers on how the boot process goes in case of 2 boot partitions on the same disk. (lots of other cases). Can someone visualize the grub flow in regards to using a chroot vs using something alike grub-install --boot-directory=/mnt/boot . How is this internally treated?
Feel free to suggest better titles for this question, I'm very bad at that.
Additionally , here's the MBR
dd if=/dev/sda of=mbr.bin bs=512 count=1
root@server20:/# file mbr.bin
mbr.bin: x86 boot sector;
partition 1: ID=0x83, starthead 32, startsector 2048, 940722176 sectors;
partition 2: ID=0x83, active, starthead 95, startsector 940724224, 1024000 sectors;
partition 3: ID=0x82, starthead 29, startsector 941748224, 2097152 sectors;
partition 4: ID=0x8e, starthead 167, startsector 943845376, 32716800 sectors, code offset 0x63
