Moving install from single disk to RAID 1

[keldek]

If you want a full run down as to WHY I want to do this, read here: webhostingtalk.com/showthread.php?t=899909

Basically, my ISP could not get my server running stable on a simple raid 1 (or raid 5) so what it came down to was having them install my system on a single disk. I don't exactly like this, main reason being, if the system (or HDD) crashes, I'll end up with another several hours of down time... So here is my proposal:

Please Note: This will have to be accomplished on a live System (full backups!) over ssh as I don't trust my ISP to do things right as described in my post above.

Current Setup:
CentOS 5.3 x86_64
Dual Xeon 5410
16GB RAM
4x 750GB HDDs

/boot - /dev/sda1 - 512MB (real 471MB) ext3
/ - /dev/sda2 - 50GB (real 46GB) ext3
/home - /dev/sda3 - remaining space (real 642GB) ext3

swap - /dev/sdb1 - 32GB
/backup - /dev/sdb2 - remaining space (real 659GB) ext3

/dev/md0 - /dev/sdc + /dev/sdd - raid 1 (NOTE: uses entire disk, no partitions!)

Proposed Solution:

vgcreate -s 64M vg0 /dev/md0

lvcreate -L 512M -n lvboot vg0
lvcreate -L 50G -n lvroot vg0
lvcreate -L 5G -n lvtmp vg0
lvcreate --extent 100%FREE -n lvhome vg0

mkfs -t ext3 -m 1 /dev/vg0/lvboot
mkfs -t ext3 -m 1 /dev/vg0/lvroot
mkfs -t ext3 -m 1 /dev/vg0/lvtmp
mkfs -t ext3 -m 1 /dev/vg0/lvhome

Now, I'd like to 'init 1' at this stage but I can't, so I won't (possible solutions?? Possible to umount the / partition??)

Assuming I'd have to do this on a fully live system, I'd disable all services that I can

/etc/init.d/sendmail stop
/etc/init.d/postfix stop
/etc/init.d/saslauthd stop
/etc/init.d/httpd stop
/etc/init.d/mysql stop
/etc/init.d/courier-authlib stop
/etc/init.d/courier-imap stop
/etc/init.d/amavisd stop
/etc/init.d/clamd stop
/etc/init.d/pure-ftpd stop
/etc/init.d/fail2ban stop
/etc/init.d/syslogd stop

Then we copy all of our data from the single partitions to the raid disks

mkdir /mnt/newroot
mkdir /mnt/newroot/boot
mkdir /mnt/newroot/tmp
mkdir /mnt/newroot/home

mount /dev/vg0/lvboot /mnt/newroot/boot
mount /dev/vg0/lvroot /mnt/newroot/root
mount /dev/vg0/lvtmp /mnt/newroot/tmp
mount /dev/vg0/lvhome /mnt/newroot/home

(I think I covered everything)

umount -l /dev/sda1 (/boot)
umount -l /dev/sda3 (/home)
cp -dpRx /* /mnt/newroot/
mount /dev/sda1 /boot
cp -dpRx /boot/* /mnt/newroot/boot/
mount /dev/sda3 /home
cp -dpRx /home/* /mnt/newroot/home/

Once we have everything copied, update /etc/fstab and /etc/mtab to reflect the changes we made:
vi /etc/fstab

LABEL=/home            /home                  ext3    defaults        0 3
LABEL=/                /                      ext3    defaults,usrquota,grpquota        1 1
LABEL=/boot            /boot                  ext3    defaults        1 2
tmpfs                  /dev/shm                tmpfs  defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                  /sys                    sysfs  defaults        0 0
proc                    /proc                  proc    defaults        0 0
LABEL=SWAP-sdb1        swap                    swap    defaults        0 0

To

/dev/vg0/lvhome  /home  ext3  defaults  0 3
/dev/vg0/lvroot  /  ext3  defaults,usrquota,grpquota  1 1
/dev/vg0/lvboot  /boot  ext3  defaults  1 2
tmpfs  /dev/shm  tmpfs  defaults  0 0
devpts  /dev/pts  devpts  gid=5,mode=620  0 0
sysfs  /sys  sysfs  defaults  0 0
proc  /proc  proc  defaults  0 0
LABEL=SWAP-sdb1  swap  swap  defaults  0 0
Moving on, we make a fail safe in the event this doesn't work out:
vi /boot/grub/menu.lst

find

default=0

add after

fallback=1

Then we find (in the same file):

title CentOS (2.6.18-164.el5)
        root (hd1,0)
        kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/vg0/vgroot
        initrd /initrd-2.6.18-164.el5.img

Add before:

title CentOS (2.6.18-164.el5)
        root (hd3,0)
        kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/sda2
        initrd /initrd-2.6.18-164.el5.img

Where (hd3,0) is /dev/sdc. If the system fails to boot to the raid then it'll auto boot to the single disk (/dev/sda)

then update my ramdisk:

mv /boot/initrd-`uname -r`.img /boot/initrd-`uname -r`.img_bak
mkinitrd /boot/initrd-`uname -r`.img `uname -r`

And now to set up grub...

grub
> root (hd0,0)
> setup (hd0)

we should see something like this:

Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.

Then

> root (hd3,0)
> setup (hd3)

Again, we should see something like this:

Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 15 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+15 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.

> quit

From here I think we're ready to reboot, can't see where I missed anything. If all goes well then I should see my volume groups listed in 'df- h'

Now, the big question is... have I missed anything?

Any and all input is greatly appreciated.

[Rubberman]

Personally, I don't like to use RAID for the system disc(s). I make regular bit image backups to an external drive which I can use to swap out the system disc in a couple of minutes (seconds because I have a removable system drive enclosure). Total down time for my RHEL/CentOS 5.4 system including boot time is 5-10 minutes at most. That said, in 2 years I've had 0 system drive failures. I use NAS RAID devices for my long-term archival storage, but not for daily runtime purposes.