Ubuntu 14.04 : use KVM within a container

Here are logs when using KVM within a container.

Host OS : Ubuntu 14.04

Container : Ubuntu 14.04

create a container.

# lxc-create -n ubuntu-cn1 -t ubuntu -- -r trusty

create /dev/kvm and /dev/net/tun character devices for the container so that the container can use KVM.

edit /var/lib/lxc/ubuntu-cn1/rootfs/etc/rc.local

Add three lines before ‘exit 0’

# grep -v ^# /var/lib/lxc/ubuntu-cn1/rootfs/etc/rc.local mkdir -p /dev/net || true mknod /dev/kvm c 10 232 mknod /dev/net/tun c 10 200 exit 0

start the container and install KVM within the container.

# lxc-start -n ubuntu-cn1 root@ubuntu-cn1:~# apt-get update root@ubuntu-cn1:~# apt-get install qemu-kvm libvirt-bin virtinst root@ubuntu-cn1:~# kvm-ok INFO: /dev/kvm exists KVM acceleration can be used

build a VM.

nnn, error.

the container can not mount loop devices.

root@ubuntu-cn1:/home/ubuntu# virt-install --connect qemu:///system -n ubuntu1404-vm1 -s 10 -r 512 -f /var/lib/libvirt/images/ubuntu1404-vm1.img --vcpus=1 --os-variant ubuntutrusty --nographics --lo cation ./ubuntu-14.04-server-amd64.iso  --extra-args='console=tty0 console=ttyS0,115200n8' --keymap ja Starting install... mount: Could not find any loop device. Maybe this kernel does not know       about the loop device? (If so, recompile or `modprobe loop'.) umount: /var/lib/libvirt/boot/virtinstmnt.1ZhSOK: not mounted ERROR    Error preparing install location Traceback (most recent call last):  File "/usr/lib/python2.7/dist-packages/virtinst/OSDistro.py", line 123, in _locationCheckWrapper    fetcher.prepareLocation()  File "/usr/lib/python2.7/dist-packages/virtinst/ImageFetcher.py", line 201, in prepareLocation    (self.location)) ValueError: Mounting location '/home/ubuntu/ubuntu-14.04-server-amd64.iso' failed ERROR    Invalid install location: Mounting location '/home/ubuntu/ubuntu-14.04-server-amd64.iso' failed Domain installation does not appear to have been successful. If it was, you can restart your domain by running:  virsh --connect qemu:///system start ubuntu1404-vm1 otherwise, please restart your installation.

There are loop devices in that container.

root@ubuntu-cn1:/home/ubuntu# ls /dev/loop* -l brw-rw---- 1 root disk 7, 0 Jan  7 16:07 /dev/loop0 brw-rw---- 1 root disk 7, 1 Jan  7 16:07 /dev/loop1 brw-rw---- 1 root disk 7, 2 Jan  7 16:07 /dev/loop2 brw-rw---- 1 root disk 7, 3 Jan  7 16:07 /dev/loop3 brw-rw---- 1 root disk 7, 4 Jan  7 16:07 /dev/loop4 brw-rw---- 1 root disk 7, 5 Jan  7 16:07 /dev/loop5 brw-rw---- 1 root disk 7, 6 Jan  7 16:07 /dev/loop6 brw-rw---- 1 root disk 7, 7 Jan  7 16:07 /dev/loop7

So the root cause on this error is .. LXC host does not allow containers to mount loop devices?

shutdown the container.

root@ubuntu-cn1:/home/ubuntu# init 0

edit /var/lib/lxc/ubuntu-cn1/config

allow the container to use /dev/loop, /dev/kvm and /dev/net/tun

root@ubuntu2-hat:~# grep -v ^# /var/lib/lxc/ubuntu-cn1/config lxc.include = /usr/share/lxc/config/ubuntu.common.conf lxc.mount.auto = cgroup lxc.aa_profile = lxc-container-default-with-nesting lxc.rootfs = /var/lib/lxc/ubuntu-cn1/rootfs lxc.mount = /var/lib/lxc/ubuntu-cn1/fstab lxc.utsname = ubuntu-cn1 lxc.arch = amd64 lxc.network.type = veth lxc.network.flags = up lxc.network.link = lxcbr0 lxc.network.hwaddr = lxc.cgroup.devices.allow = b 7:* rwm lxc.cgroup.devices.allow = c 10:230 rw lxc.cgroup.devices.allow = c 10:232 rw

start the container

# lxc-start -n ubuntu-cn1

build a VM.okay.

root@ubuntu-cn1:/home/ubuntu# virt-install --connect qemu:///system -n ubuntu1404-vm1 -s 10 -r 512 -f /var/lib/libvirt/images/ubuntu1404-vm1.img --vcpus=1 --os-variant ubuntutrusty --nographics --lo cation ./ubuntu-14.04-server-amd64.iso  --extra-args='console=tty0 console=ttyS0,115200n8' --keymap ja Starting install...

The VM “ubuntu1404-vm1” is running within the container “ubuntu-cn1”.

root@ubuntu-cn1:~# virsh list --all Id    Name                           State ---------------------------------------------------- 3     ubuntu1404-vm1                 running root@ubuntu-cn1:~# root@ubuntu-cn1:~# virsh console 3 Connected to domain ubuntu1404-vm1 Escape character is ^] hattori@ubuntu:~$