I'm trying to migrate from physical machine to virtual machine GNU/Linux with KVM, continuing keeping running the physical machine during the virtualization (and thus minimization the downtime).
(still working in progress, but...)
Script to create the virtual disk with 2 partitions:
#!/bin/bash
set -e
if [ ! $UID -eq 0 ] ; then
echo "You are not root"
exit 1
fi
DEFAULT=5 # GB
ROOTSIZEGB=${1:-$DEFAULT}
ROOTSIZEB=$((ROOTSIZEGB * 1024 * 1024 * 1024 )) # bytes
ROOTSIZEs=$((ROOTSIZEB / 512 )) # sector
SWAPSIZEGB=4 # GB
SWAPSIZEB=$((SWAPSIZEGB * 1024 * 1024 * 1024 )) # bytes
SWAPSIZEs=$((SWAPSIZEB / 512 )) # sector
# 4K alignment:
#OFFSETKB=64 # KB
OFFSETKB=1024 # KB
OFFSETB=$((OFFSETKB * 1024 )) # bytes
OFFSETs=$((OFFSETB / 512 )) # sector
DEFAULT=1
N=${2:-$DEFAULT}
LOOP=/dev/loop$N
VDISK=disk-0$N.bin
LOGFILE=$VDISK.log
if [ -f $VDISK ] ; then
echo "$VDISK already exists!"
echo "usage: $0 GBsize LOOPdevice"
ls -lh $VDISK
mount | grep $LOOP
echo "# umount /mnt/$VDISK"
losetup -a
echo "# losetup -d $LOOP"
exit 1
fi
echo "Virtual file system : $VDISK : $ROOTSIZEGB GB / + $SWAPSIZEGB swap mounted on $LOOP"
echo "Ok? (CTRL-C to quit, ENTER to continue)"
read ANSWER
CMD="qemu-img create -f raw $VDISK $((OFFSETB + ROOTSIZEB + SWAPSIZEB))"
echo "--------" | tee -a $LOGFILE
echo $CMD | tee -a $LOGFILE
echo "--------" | tee -a $LOGFILE
$CMD
#CMD="$OFFSETs,$ROOTSIZEs,83\n$((OFFSETs + ROOTSIZEs)),$((SWAPSIZEs - OFFSETs)),82"
CMD="$OFFSETs,$ROOTSIZEs,83\n$((OFFSETs + ROOTSIZEs)),,82"
echo "--------" | tee -a $LOGFILE
echo -e "$CMD | sfdisk -S 32 -uS $VDISK" | tee -a $LOGFILE
echo "--------" | tee -a $LOGFILE
echo -e "$CMD" | sfdisk -S 32 -uS $VDISK > /dev/null 2>&1
# check:
echo "--------" | tee -a $LOGFILE
sfdisk -l -S 32 -uS $VDISK | tee -a $LOGFILE
echo "--------" | tee -a $LOGFILE
LOOPSWAP=/dev/loop7
CMD="losetup --offset $(( OFFSETB + ROOTSIZEB )) $LOOPSWAP $VDISK"
echo -e "--------\n$CMD\n--------" | tee -a $LOGFILE
$CMD
mkswap $LOOPSWAP
sleep 1
losetup -d $LOOPSWAP
mkdir -p /mnt/$VDISK
CMD="losetup --offset $OFFSETB $LOOP $VDISK"
echo -e "--------\n$CMD\n--------" | tee -a $LOGFILE
$CMD
CMD="mkfs.ext4 -O uninit_bg,filetype,extent,dir_index -L KVM $LOOP"
echo -e "--------\n$CMD\n--------" | tee -a $LOGFILE
$CMD > /dev/null 2>&1
CMD="mount $LOOP /mnt/$VDISK"
echo -e "--------\n$CMD\n--------" | tee -a $LOGFILE
$CMD
#grub-install --force --boot-directory=/mnt/test-sda/ --no-floppy $LOOP
echo "At the end...:"
echo "umount $LOOP ; losetup -d $LOOP" | tee -a $LOGFILE
Clone physical machine:
cd /mnt/$VDISK rsync -e ssh -au -numeric-ids --stats -h --exclude /proc --exclude /tmp --exclude /dev --exclude /sys root@REMOTEHOST:/ /mnt/$VDISK/
Chroot to VM:
mount --bind /dev/ /mnt/$VDISK/dev/ mount -t devpts pts /mnt/$VDISK/dev/pts/ mount -t tmpfs none /mnt/$VDISK/dev/shm/ mount -t proc none /mnt/$VDISK/proc/ mount -t sysfs sys /mnt/$VDISK/sys/ chroot /mnt/test/sda
Fix mtab and fstab:
vim /etc/mtab vim /etc/fstab
Rebuild initramdisk:
mkinitrd ...
Install grub:
grub-install $LOOP
Umounting virtual image:
exit cd .. umount /mnt/$VDISK/sys/ umount /mnt/$VDISK/proc/ umount /mnt/$VDISK/dev/shm umount /mnt/$VDISK/dev/pts umount /mnt/$VDISK/dev/ umount /mnt/$VDISK/ losetup -d $LOOP
Run virtual machine:
kvm -name VMclone -m 4096 -cpu kvm32 -monitor stdio -kernel boot/vmlinuz -append "root=/dev/sda1" -initrd initrd.img $VDISK
grub:
linux /boot/vmlinux... root=/dev/sda1 initrd /boot/initrd.... boot
