Node Installation

This guide intends to describe the process of creating a compute node based on Raspbian on a Raspberry Pi 3. You will need a microSD card with at least 4GB and preferably class 10 or better.

Warning

Please note that there are images ready to be dumped on a microSD card that will save you the trouble of this guide. This guide is only intended to show what is inside those images and for those who want to contribute and improve this process.

Note

  • Read Notes sections attached to some steps, before using the shell
  • Commands prefixed by “#” are meant to be run as root. Commands prefixed by “$” must be run as a normal user.
  • (...) in code snippets means that could be code before/after the modified lines. That portion of code need to stay unmodified.

1. Install Raspbian on the Raspberry Pi

You can check the steps here https://www.raspberrypi.org/documentation/installation/installing-images/.

1.1. Upgrade to stretch

Change repositories and upgrade system:

echo "deb http://archive.raspbian.org/raspbian/ stretch main contrib non-free rpi" > /etc/apt/sources.list
echo "deb http://archive.raspberrypi.org/debian/ stretch main ui" > /etc/apt/sources.list.d/raspi.list
apt update
apt upgrade

2. Install the required software

2.1. Install required packages

apt install snapd bridge-utils python-pip python-ws4py git ruby genisoimage
pip install idna==2.5
pip install pylxd==2.0.5
pip install isoparser

2.2. Disable apparmor service

Apparmor can cause problems when installing packages via snaps. You can stop it and disable it from automatic start by executing:

systemctl stop apparmor.service
systemctl disable apparmor.service

2.3. Install LXD as Snap

snap install lxd --channel=2.0/stable

Some apps like pylxd and LXDoNe will assume lxd is installed on /var/lib/lxd. Because we are using LXD through a snap, the installation folder is in another location, so we will create a symbolic link for compatibility with pylxd and LXDoNe.

ln -s /var/snap/lxd/common/lxd/ /var/lib/lxd

3. Initial Configurations

3.1. Configure network bridge

Now let us configure the bridge that will be used by all containers deployed. Configure it in /etc/network/interfaces. Your configuration should look something like this:

auto lo
iface lo inet loopback

#auto eth0
#iface eth0 inet dhcp

auto br0
iface br0 inet static
        address 10.8.2.38
        netmask 255.255.255.0
        gateway 10.8.2.1
        bridge_ports eth0
        bridge_fd 0
        bridge_maxwait 0

Reboot to apply changes:

reboot

3.2. Initialize LXD

If you never used snapd before, you’ll need to update your PATH for using lxd as root user:

echo "PATH=\"/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin\"" >> /etc/environment
source /etc/environment && export PATH

And for use it with sudo modify /etc/sudoers replacing:

(...)
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
(...)

by:

(...)
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games:/snap/bin"
(...)

Provide initial configuration for LXD:

lxd init

Press enter on the first two questions to select default value. On the third question, “Do you want to configure the LXD bridge?”, answer “no”. We won’t use that bridge, instead we will let OpenNebula to do this job.

3.2.1. Modify Network inside LXD default profile

Containers inherit properties from a profile. The default profile contains a network device, we’ll remove this one as it’s not managed by OpenNebula.

lxc profile device remove default eth0

4. Configure the RPi as a node for OpenNebula

4.1. Install OpenNebula node packages and dependencies

Download opennebula-common package and install it:

dpkg -i opennebula-common_5.2.1-1_all.deb

4.2. Configure oneadmin user to correctly use lxd

Assign sudo permission to oneadmin and add it to lxd group

echo "oneadmin ALL= NOPASSWD: ALL" >> /etc/sudoers
usermod -a -G lxd oneadmin

To use lxd as sudo with oneadmin user, in /etc/sudoers.d/opennebula replace

Defaults:oneadmin secure_path = /sbin:/bin:/usr/sbin:/usr/bin

by:

Defaults:oneadmin secure_path = /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games:/snap/bin

4.3. Configure Passwordless SSH

OpenNebula Front-end connects to the hypervisor Hosts using SSH. You must distribute the public key of oneadmin user from all machines to the file /var/lib/one/.ssh/authorized_keys in all the machines. There are many methods to achieve the distribution of the SSH keys, ultimately the administrator should choose a method (the recommendation is to use a configuration management system). In this guide we are going to manually scp the SSH keys.

When the package was installed in the Front-end, an SSH key was generated and the authorized_keys populated. We will sync the id_rsa, id_rsa.pub and authorized_keys from the Front-end to the nodes. Additionally we need to create a known_hosts file and sync it as well to the nodes. To create the known_hosts file, we have to execute this command as user oneadmin in the Front-end with all the node names and the Front-end name as parameters:

ssh-keyscan <frontend> <node1> <node2> <node3> ... >> /var/lib/one/.ssh/known_hosts

Now we need to copy the directory /var/lib/one/.ssh to all the nodes. The easiest way is to set a temporary password to oneadmin in all the hosts and copy the directory from the Front-end:

scp -rp /var/lib/one/.ssh <node1>:/var/lib/one/
scp -rp /var/lib/one/.ssh <node2>:/var/lib/one/
scp -rp /var/lib/one/.ssh <node3>:/var/lib/one/
...

You should verify that connecting from the Front-end, as user oneadmin, to the nodes and the Front-end itself, and from the nodes to the Front-end, does not ask password:

ssh <frontend>
exit
ssh <node1>
ssh <frontend>
exit
exit
ssh <node2>
ssh <frontend>
exit
exit
ssh <node3>
ssh <frontend>
exit
exit

4.4. Install VNC server

We compiled and provided it for Raspbian Stretch in our releases. Download it from the latest release and install the required dependencies from repositories.

sudo dpkg -i <path_to>/svncterm_1.2-1_armhf.deb

5. Connect

Now you are done and ready to connect the new node to your cloud. I know, I know, it’s easier to download a pre-made image from clox.org but it always feels better to do it yourself. Either that or you are feeling really annoyed knowing all the time you could have saved yourself with the pre-made image :)