Saturday, December 20, 2014

Virtualizing old Centos 5 server with software RAID disks

VMware Converter does decent job converting old physical servers to virtual machines, but it refuses to do anything to servers using software RAID. I really don't get why such arbitary limitation is in place. It really doesn't matter if physical server used RAID, software or not, because everything is copied by Converter on file lever rather than block level.


Source: CentOS 5.10 x64, two SATA disks (AHCI), mdraid mirror, no LVM, swap, /boot and / only, text only (no GUI)
Target: VMware ESXi 5.1 virtual machine, LSI SAS, single disk, Intel E1000

# Boot TARGET machine in rescue mode using CentOS 5.10 install ISO image ("linux rescue")
# Start networking and enter IP information when prompted
# Skip searching of existing installs
# You're now in bash shell

# Verify network connectivity to SOURCE server
ping 10.10.53.11
ssh root@10.10.53.11

# Make sure you disconnect that SSH test session so you don't destroy source server
# with following commands...

# Remember you have two ttys available, ALT+F1, ALT+F2

# Create new partitions on TARGET server
# /boot, swap, root
parted -s /dev/sda \
       mklabel msdos \
       mkpart primary 4MiB 200MiB \
       set 1 boot on \
       mkpart primary linux-swap 200MiB 6GiB \
       mkpart primary 6GiB 100% \
       print

# Format new filesystems and swap
mkfs.ext3 -L"boot" /dev/sda1
mkswap /dev/sda2
mkfs.ext3 -L"root" /dev/sda3

# Mount new filesystems
mkdir -p /newsys
mount /dev/sda3 /newsys
mkdir -p /newsys/boot
mount /dev/sda1 /newsys/boot

# On SOURCE: Before running rsync make sure you stop any services that may modify essential files
# If it's critical server and you need to minimize downtime do below rsync commands twice
# First to sync bulk of files and second (with SOURCE services down) to sync changes

# Rsync /boot from SOURCE to TARGET
# Be careful with use of trailing backslashes, must on source, never on target
rsync --progress -aAxXv -e ssh root@10.10.53.11:/boot/ /newsys/boot

# Rsync / from SOURCE to TARGET
# Since rsync is limited to single filesystem (lowercase x parameter)
# we don't need to exclude /proc, /sys, /dev etc.
rsync --progress -aAxXv -e ssh root@10.10.53.11:/ /newsys

# If you need to exclude some junk on old server try something like
# rsync --progress -aAxXv --exclude={"/trash/*","/nonpd/*"} -e ssh root@10.10.53.11:/ /newsys

# Before chrooting on TARGET we need few extra mountpoints
mount -t proc   proc /newsys/proc
mount -t sysfs  sys  /newsys/sys
mount -o bind   /dev /newsys/dev
mount -t devpts pts  /newsys/dev/pts

# mtab needs some mangling
cat /etc/mtab | grep /newsys | sed -e's|/newsys|/|g' -e's|//|/|g' > /newsys/etc/mtab

# chroot to new system
LANG=C chroot /newsys /bin/bash

# remove old mdraid disk mounts from TARGET /etc/fstab
# edit /etc/fstab so swap, /boot and / device names are correct
#
# old:
# /dev/md1      /       ext3  defaults   1 1
#
# new:
# /dev/sda3     /       ext3  defaults   1 1
#
# so root is /dev/sda3, /boot is /dev/sda1 and swap /dev/sda2
# watch for lines getting wrapped!
#

# fix grub parameters
# edit /etc/grub.conf and change old root=/dev/md1 to root=/dev/sda3

# edit /etc/sysconfig/network-scripts/ifcfg-eth0
# and remove "HWADDR" line entirely

# fix boot sector
/sbin/grub-install --recheck --root-directory=/ /dev/sda

# redo initramdisk
# use proper kernel version (i.e. same as SOURCE used)
# this is to ensure initrd has drivers for our disk controller
# kernel running on rescue mode probably doesn't match with one 
# in install we're migrating so no "uname -r" here
/sbin/mkinitrd --force-scsi-probe -f /boot/initrd-2.6.18-371.el5.img 2.6.18-371.el5

# exit chroot and reboot
exit
reboot

# Watch out for IP conflicts if you have both SOURCE and TARGET running!



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