LXC

From Alpine Linux
Revision as of 17:20, 18 June 2014 by ScrumpyJack (talk | contribs)
Jump to: navigation, search

Linux Containers (LXC) provides containers similar BSD Jails, Linux VServer and Solaris Zones. It gives the impression of virtualization, but shares the kernel and resources with the "host".

Installation

Install the required packages:

apk add lxc lxc-templates bridge

Prepare network on host

Set up a bridge on the host. Example /etc/network/interfaces:

auto br0
iface br0 inet dhcp
    bridge-ports eth0

Create a network configuration template for the guests, /etc/lxc/lxc.conf:

lxc.network.type = veth
lxc.network.link = br0
lxc.network.flags = up

Create a guest

Alpine Template

lxc-create -n guest1 -f /etc/lxc/lxc.conf -t alpine

This will create a /var/lib/lxc/guest1 directory with a config file and a rootfs directory.

Note that by default alpine template does not have networking service on, you will need to add it using lxc-console


If running on x86_64 architecture, it is possible to create a 32bit guest:

lxc-create -n guest1 -f /etc/lxc/lxc.conf -t alpine -- --arch x86

Debian template

In order to create a debian template container you will need to install some packages:

apk add debootstrap rsync

Also you will need to turn off some grsecurity chroot options otherwise the debootstrap will fail:

echo 0 > /proc/sys/kernel/grsecurity/chroot_caps echo 0 > /proc/sys/kernel/grsecurity/chroot_deny_chroot echo 0 > /proc/sys/kernel/grsecurity/chroot_deny_mount echo 0 > /proc/sys/kernel/grsecurity/chroot_deny_mknod echo 0 > /proc/sys/kernel/grsecurity/chroot_deny_chmod

Please remember to turn them back on, or just simply reboot the system.


Now you can run:

SUITE=wheezy lxc-create -n guest1 -f /etc/lxc/lxc.conf -t debian

Starting/Stopping the guest

Create a symlink to the /etc/init.d/lxc script for your guest.

ln -s lxc /etc/init.d/lxc.guest1

You can start your guest with:

/etc/init.d/lxc.guest1 start

Stop it with:

/etc/init.d/lxc.guest1 stop

Make it autostart on boot up with:

rc-update add lxc.guest1

Connecting to the guest

By default sshd is not installed, so you will have to connect to a virtual console. This is done with:

lxc-console -n guest1

To disconnect from it, press Ctrl+a q

Deleting a guest

Make sure the guest is stopped and run:

lxc-destroy -n guest1

This will erase everything, without asking any questions. It is equivalent to:

rm -r /var/lib/lxc/guest1

Advanced

Creating a LXC container without modifying your network interfaces

The problem with bridging is that the interface you bridge gets replaced with your new bridge interface. That is to say that say you have an interface eth0 that you want to bridge, your eth0 interface gets replaced with the br0 interface that you create. It also means that the interface you use needs to be placed into promiscuous mode to catch all the traffic that could de destined to the other side of the bridge, which again may not be what you want.

The solution is to create a dummy network interface, bridge that, and set up NAT so that traffic out of your bridge interface gets pushed through the interface of your choice.

So, first, lets create that dummy interface

modprobe dummy

This will create a dummy interface called dummy0

Now we will create a bridge called br0

brctl addbr br0 brctl setfd br0 0

and then make that dummy interface one end

brctl addif br0 dummy0

Next, let's give that bridged interface a reason to exists

ip add add 192.168.1.1/24 dev br0

Create a file for your container, let's say /etc/lxc/bridgenat.conf, with the following settings.

lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = br0
lxc.network.name = eth1
lxc.network.ipv4 = 192.168.1.2/24

and build your container with that file

lxc-create -n alpine -f /etc/lxc/bridgenat.conf -t alpine


Using static IP

If you're using static IP, you need to configure this properly on guest's /etc/network/interfaces. To stay on the above example, modify /var/lib/lxc/guest1/rootfs/etc/network/interfaces

from

#auto lo
    iface lo inet loopback
auto eth0
    iface eth0 inet dhcp

to

#auto lo
    iface lo inet loopback
auto eth0
    iface eth0 inet static
    address <lxc-container-ip>   # IP which the lxc container should use
    gateway <gateway-ip>         # IP of gateway to use, mostly same as on lxc-host
    netmask <netmask>

mem and swap

vim /boot/extlinux.conf

APPEND initrd=initramfs-3.10.13-1-grsec root=UUID=7cd8789f-5659-40f8-9548-ae8f89c918ab modules=sd-mod,usb-storage,ext4 quiet cgroup_enable=memory swapaccount=1

checkconfig

lxc-checkconfig

Kernel configuration not found at /proc/config.gz; searching... Kernel configuration found at /boot/config-3.10.13-1-grsec --- Namespaces --- Namespaces: enabled Utsname namespace: enabled Ipc namespace: enabled Pid namespace: enabled User namespace: missing Network namespace: enabled Multiple /dev/pts instances: enabled --- Control groups --- Cgroup: enabled Cgroup clone_children flag: enabled Cgroup device: enabled Cgroup sched: enabled Cgroup cpu account: enabled Cgroup memory controller: missing Cgroup cpuset: enabled --- Misc --- Veth pair device: enabled Macvlan: enabled Vlan: enabled File capabilities: enabled Note : Before booting a new kernel, you can check its configuration usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig

VirtualBox

In order for network to work on containers you need to set "Promiscuous Mode" to "Allow All" in VirtualBox settings for the network adapter.

VirtualBoxNetworkAdapter.jpg

LXC 1.0 Additional information

Some info regarding new features in LXC 1.0

https://www.stgraber.org/2013/12/20/lxc-1-0-blog-post-series/