LXCize the KVM machine

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In order to make exsiting kvm based machine to be lxc container, following is the steps.
Refers to:
https://www.stgraber.org/2012/03/04/booting-an-ubuntu-12-04-virtual-machine-in-an-lxc-container/

Convert Disk Formats

First we want to convert the qcow2 format image to raw format, by following command:

$ qemu-img convert u12-debug-ui.qcow2 Contrail.raw

This will take a very long time, because qcow2 file will expand to a whole images, like mine, the Contrail.raw in fact expands to 100G size.

LXC the KVM

Since we have the raw image file, we could create a new configuration file for starting the machine:

 myvm.conf
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = br0
lxc.network.name = eth0
lxc.network.ipv4 = xxx.xxx.10.230/24
lxc.network.ipv4.gateway = xxx.xxx.0.176
#lxc.network.link = lxcbr0
lxc.utsname = myvminlxc

lxc.tty = 4
lxc.pts = 1024
lxc.rootfs = /dev/mapper/loop0p1
lxc.arch = amd64
lxc.cap.drop = sys_module mac_admin

lxc.cgroup.devices.deny = a
# Allow any mknod (but not using the node)
lxc.cgroup.devices.allow = c *:* m
lxc.cgroup.devices.allow = b *:* m
# /dev/null and zero
lxc.cgroup.devices.allow = c 1:3 rwm
lxc.cgroup.devices.allow = c 1:5 rwm
# consoles
lxc.cgroup.devices.allow = c 5:1 rwm
lxc.cgroup.devices.allow = c 5:0 rwm
#lxc.cgroup.devices.allow = c 4:0 rwm
#lxc.cgroup.devices.allow = c 4:1 rwm
# /dev/{,u}random
lxc.cgroup.devices.allow = c 1:9 rwm
lxc.cgroup.devices.allow = c 1:8 rwm
lxc.cgroup.devices.allow = c 136:* rwm
lxc.cgroup.devices.allow = c 5:2 rwm
# rtc
lxc.cgroup.devices.allow = c 254:0 rwm
#fuse
lxc.cgroup.devices.allow = c 10:229 rwm
#tun
lxc.cgroup.devices.allow = c 10:200 rwm
#full
lxc.cgroup.devices.allow = c 1:7 rwm
#hpet
lxc.cgroup.devices.allow = c 10:228 rwm
#kvm
lxc.cgroup.devices.allow = c 10:232 rwm

Now setup the image file via, this will use the /dev/mapper/loop0p1 as the root partition:

$ sudo kpartx -a Contrail.img

Now start the machine via:

$ sudo lxc-start -n myvminlxc -f ./myvm.conf

Your machine will boot into the lxc, and its behavior is the same as the kvm based machine.

TroubleShooting

The root could not login into the lxc, because of the selinux enabled in the Ubuntu Host, simply disable it in /etc/selinux/config by:

$ sudo vim /etc/selinux/config
#SELINUX=permissive
SELINUX=disabled

Added it into the startup file in /etc/rc.local, it’s ugly, and it will cause the first tty died. But, first use it:

kpartx -a /home/xxxxx/iso/Contrail.raw
lxc-start -n myvminlxc -f /home/xxxxx/iso/myvm.conf