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How to set up nodes via LXC

Debian Testing:

(refer to https://wiki.debian.org/LXC)

aptitude install lxc bridge-utils libvirt-bin debootstrap dnsmasq

Add this line to /etc/fstab:

cgroup  /sys/fs/cgroup  cgroup  defaults  0   0

Mount ze cgroup

mount /sys/fs/cgroup

Apply google and kernel parameters until checkconfig passes:

lxc-checkconfig

Create a VM or five

lxc-create -n n1 -t debian -- --release jessie
lxc-create -n n2 -t debian -- --release jessie
lxc-create -n n3 -t debian -- --release jessie
lxc-create -n n4 -t debian -- --release jessie
lxc-create -n n5 -t debian -- --release jessie

Fire up each VM:

lxc-start --name n1

And set your root password--I use root/root by default in Jepsen.

passwd

Copy your SSH key

cat ~/.ssh/id_rsa.pub

and add it to root's authorized_keys:

apt-get install -y sudo vim
mkdir ~/.ssh
chmod 700 ~/.ssh
touch ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys
vim ~/.ssh/authorized_keys

Enable password-based login for root (used by jsch):

sed  -i 's,^PermitRootLogin .*,PermitRootLogin yes,g' /etc/ssh/sshd_config
systemctl restart sshd

Shut each one down with poweroff so we can set up the network.

Drop entries in ~/.ssh/config for nodes:

Host n*
User root

Edit /var/lib/lxc/n1/config, changing the network hwaddr to something unique. I suggest using sequential mac addresses for n1, n2, n3, ....

# Template used to create this container: /usr/share/lxc/templates/lxc-debian
# Parameters passed to the template:
# For additional config options, please look at lxc.conf(5)

lxc.rootfs = /var/lib/lxc/n1/rootfs

# Common configuration
lxc.include = /usr/share/lxc/config/debian.common.conf

# Container specific configuration
lxc.mount = /var/lib/lxc/n1/fstab
lxc.utsname = n1
lxc.arch = amd64

# Stuff to add:
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = virbr0
lxc.network.ipv4 = 0.0.0.0/24
lxc.network.hwaddr = 00:1E:62:AA:AA:AA

Set up libvirt network, and assign MAC->IP bindings for the LXC node mac addrs

virsh net-edit default
<network>
  <name>default</name>
  <uuid>08063db9-38f4-4c9c-8887-08000f13ce80</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:8e:29:d2'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.11' end='192.168.122.100'/>
      <host mac='00:1E:62:AA:AA:AA' name='n1' ip='192.168.122.11'/>
      <host mac='00:1E:62:AA:AA:AB' name='n2' ip='192.168.122.12'/>
      <host mac='00:1E:62:AA:AA:AC' name='n3' ip='192.168.122.13'/>
      <host mac='00:1E:62:AA:AA:AD' name='n4' ip='192.168.122.14'/>
      <host mac='00:1E:62:AA:AA:AE' name='n5' ip='192.168.122.15'/>
    </dhcp>
  </ip>
</network>

Drop an entry in /etc/resolv.conf to read from the libvirt network dns:

nameserver 192.168.122.1  # Local libvirt dnsmasq
nameserver 192.168.1.1    # Regular network resolver

Kill the system default dnsmasq (if you have one), and start the network (which in turn will start a replacement dnsmasq with the LXC config. Then, start up all the nodes. I have this in a bash script called jepsen-start:

#!/bin/sh
sudo service dnsmasq stop
sudo virsh net-start default
sudo lxc-start -d -n n1
sudo lxc-start -d -n n2
sudo lxc-start -d -n n3
sudo lxc-start -d -n n4
sudo lxc-start -d -n n5
cssh n1 n2 n3 n4 n5

Store the host keys unencrypted so that jsch can use them:

for n in $(seq 1 5); do ssh-keyscan -t rsa n$n; done >> ~/.ssh/known_hosts

And that should mostly do it, I think.

Ubuntu 14.04 / trusty

Follow generally the same steps as for Debian, but the process is easier. Reference: https://help.ubuntu.com/lts/serverguide/lxc.html

  • right after you have installed LXC, create or open /etc/lxc/dnsmasq.conf and add the following contents:

dhcp-host=n1,10.0.3.101 dhcp-host=n2,10.0.3.102 dhcp-host=n3,10.0.3.103 dhcp-host=n4,10.0.3.104 dhcp-host=n5,10.0.3.105


10.0.3.* is LXC's default network. If you want others, go for it but you'll have to change it in the main configuration for lxc as well.

* you may not need to add cgroup to fstab and/or mount it. /sys/fs/cgroups may already be there.
* Then, go and run the lxc-create command, but...
* no need to edit /var/lib/lxc/*/config or set up a bridge, LXC does that for you.
* Fire up the boxes (lxc-start -n n{1,2,3,4,5} -d) and you should be able to ssh right into them.
* Follow the rest of the Debian tutorial, but make sure to use the correct ip addresses.