Creating a Virtual Machine from an Existing one Manually

Back to: Xen on Debian

Assuming an LVM setup, this is the command for allocating the required disk space (in this example 20Gb) for the main disk of the virtual machine. Another amount is required for the swap space.

lvcreate -L20G -n machine-name volumegroup-name lvcreate -L2G -n machine-name-swap volumegroup-name

where machine-name and volumegroup-name are specific to the specific setup.

The virtual units are formatted

mkfs.ext4 /dev/volumegroup-name/machine-name mkswap /dev/volumegroup-name/machine-name-swap

At this point the base filesystem should be copied. First mount the partition:

mount /dev/volumegroup-name/machine-name /mnt/some-directory

You must copy the existing machine filesystem except for the directories /proc and /dev. Sometimes you must skip /home or other diretories. First create a file with the list of the directories to skip:

File: ./ex

/proc
/sys

Then use rsync to copy the whole filesystem.

rsync -av --exclude-from ex 192.168.66.120:/ /mnt/some-directory/

After the file copy, it is necessary to edit some configuration files: securetty, inittab and fstab. First edit securetty

vi securetty

A line containing hvc0 should be in the file.

File: /etc/securetty

#...

# IBM iSeries/pSeries virtual console
hvc0
hvc1
#...

Then search inittab for a line with tty like the one below:

File: /etc/inittab

#c1:12345:respawn:/sbin/agetty 38400 tty1 linux

and edit it to:

File: /etc/inittab

c1:12345:respawn:/sbin/agetty 38400 hvc0 linux

Next, edit fstab to reflect the virtual drive configuration

File: /etc/fstab

/dev/xvda1               /                       ext3    defaults        1 1
/dev/xvda4               swap                    swap    defaults        0 0
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

It is important that in the moment the files were copied, the directories /proc and /dev had been left out. Now it is important to create those directories. With the partition mounted create the directories:

cd /mnt/some-directory mkdir proc dev

And then create the devices for the virtual machines

cd /mnt/some-directory/dev mknod xvc0 c 204 191 mknod hvc0 c 229 0 mknod xvda b 202 0 mknod xvda1 b 202 1