LXC on Ubuntu 10.10 for Minecraft Server

My family has all taken to Minecraft.  We got accounts for all six of us, two “grown ups”, two teens, and two little guys.  We quickly decided that we would run three different servers.  The grown up server is where we build things.  The teen server is where they grant themselves TNT and blow up everything.  And the little kid server is a kind of a combination of both.

Originally, I put them all on the same physical server and tried different port numbers.  That works, but wasn’t ideal.  We wanted our own IP addresses.  Less confusion, especially for the little guys.  I have enough hardware that we ran one instance on each server.  That was fine until I lost the grown up server due to hardware failure on the root partition.  I still can’t believe I didn’t use RAID.

Because of the desire for seperate IP addresses for each instance, and the desire to avoid total loss again, I decided to use Linux containers (LXC).  Here is my notes for getting minecraft servers up and running in a linux container.

I put the mincraft data into it’s own LVM partition because I’m going to use DRBD once I rebuild my other server.

(These are notes so they have very little explanation)

Get what we need installed
apt-get install lxc vlan bridge-utils python-software-properties screen libvirt-bin debootstrap

Create the partitions
lvcreate -L 2g -n minecraft1 datavg
mkfs.ext4 /dev/datavg/minecraft1

mkdir -p /data/minecraft1
vi /etc/fstab
/dev/datavg/minecraft1 /data/minecraft1 ext4 defaults 0 2
We need a root file system.  My main OS is 64bit.  Since the kernel in the LXC instances is the same as the host, I didn’t see a reason to get the 32bit root.

mkdir /data/images
cd /data/images
wget http://download.openvz.org/template/precreated/ubuntu-10.10-x86_64.tar.gz

mount /data/minecraft1
cd /data/minecraft1
mkdir roofs
cd rootfs
tar zxvf /data/images/ubuntu-10.10-x86_64.tar.gz .
cp /etc/resolv.conf ./etc
echo route add default gw 192.168.1.1 >> ./etc/rc.local
vi ./etc/rc.local (move the route to be above the 'exit' statement)
Update sources (http://repogen.simplylinux.ch/)
vi ./etc/apt/sources.list
deb http://us.archive.ubuntu.com/ubuntu/ maverick main restricted universe multiverse
deb http://us.archive.ubuntu.com/ubuntu/ maverick-security main restricted universe multiverse
deb http://us.archive.ubuntu.com/ubuntu/ maverick-updates main restricted universe multiverse
deb http://archive.canonical.com/ubuntu maverick partner

Chroot so we can update
chroot /data/minecraft1/rootfs /bin/bash

Get SSH up
update-rc.d ssh defaults
In the change root, you want to add your accounts and change the passwords you need to before the server comes up.
Install Sun JRE (to run minecraft server)
apt-get update
apt-get upgrade
apt-get install sun-java6-jre
exit

LXC config files
cd /data/minecraft1
vi fstabnone /data/minecraft1/rootfs/dev/pts devpts defaults 0 0
none /data/minecraft1/rootfs/proc    proc   defaults 0 0
none /data/minecraft1/rootfs/sys     sysfs  defaults 0 0
none /data/minecraft1/rootfs/dev/shm tmpfs  defaults 0 0
vi minecraft1.conf# Container with network virtualized using a pre-configured bridge named br0 and
# veth pair virtual network devices
lxc.utsname = minecraft1
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = br0
lxc.network.name = eth0
lxc.network.hwaddr = 4a:49:43:49:79:bf
lxc.network.ipv4 = 192.168.1.11/24
lxc.tty = 6
lxc.mount = /data/minecraft1/fstab
lxc.rootfs = /data/minecraft1/rootfs

Configure networking.  I have two interfaces.  I left eth0 alone and added eth1 to be the bridged interface.

vi /etc/network/interfacesauto br0
iface br0 inet static
address 192.168.1.10
netmask 255.255.255.0
broadcast 192.168.1.255
bridge_ports eth1
bridge_stp off
bridge_fd 0
bridge_maxwait 0
post-up /usr/sbin/brctl setfd br0 0
/etc/init.d/networking restart

Start the container

lxc-create -n minecraft1 -f /data/minecraft1/minecraft1.conf
lxc-ls
lxc-start -n minecraft1 init

The container has started.  SSH to it.

ssh 192.168.1.11
Minecraft server setup
This is how I get a vanilla multiplayer server running

mkdir -p /minecraft
cd /minecraft

vi update_minecraft_server.sh
#!/bin/bash
rm /minecraft/minecraft_server.jar
cd /minecraft
wget http://minecraft.net/download/minecraft_server.jar

chmod 755 update_minecraft_server.sh

vi start_minecraft_server.sh
#!/bin/bash
java -Xmx2048M -Xms2048M -jar minecraft_server.jar nogui

chmod 755 start_minecraft_server.sh
To start the server:

screen
cd /minecraft
./update_minecraft_server.sh
./start_minecraft_server.sh