Building a CoreOS Cluster

This guide takes you through building a CoreOS cluster on Brightbox. It assumes you have already signed up and configured the command line interface. If you haven’t, follow the Getting Started guide.

Everything here can also be achieved with the Brightbox Manager graphical user interface.

Setting up the firewall policy

First of all, let’s create a server group to put the new servers into:

$ brightbox groups create -n "coreos"

Creating a new server group

 id         server_count  name  
---------------------------------
 grp-cdl6h  0             coreos
---------------------------------

And then create a firewall policy for the group using its identifier:

$ brightbox firewall-policies create -n "coreos" grp-cdl6h

 id         server_group  name  
---------------------------------
 fwp-dw0n6  grp-cdl6h     coreos
---------------------------------

Firewall rules

Now let’s define the firewall rules for this new policy. First we’ll allow ssh access in from anywhere:

$ brightbox firewall-rules create --source any --protocol tcp --dport 22 fwp-dw0n6

 id         protocol  source  sport  destination  dport  icmp_type  description
--------------------------------------------------------------------------------
 fwr-i513z  tcp       any     -      -            22     -                     
--------------------------------------------------------------------------------

And then we’ll allow the CoreOS etcd ports 7001 and 4001, allowing access from only the other nodes in the group.

$ brightbox firewall-rules create --source grp-cdl6h --protocol tcp --dport 7001,4001 fwp-dw0n6

 id         protocol  source     sport  destination  dport      icmp_type  description
---------------------------------------------------------------------------------------
 fwr-xax48  tcp       grp-cdl6h  -      -            7001,4001  -                     
---------------------------------------------------------------------------------------

And then allow all outgoing access from the servers in the group:

$ brightbox firewall-rules create --destination any fwp-dw0n6

 id         protocol  source  sport  destination  dport  icmp_type  description
--------------------------------------------------------------------------------
 fwr-dtzim  -         -       -      any          -      -                     
--------------------------------------------------------------------------------

Find the CoreOS server image

At this stage, we could download the CoreOS OpenStack image (which works on Brightbox) and register it with the image libary which is pretty easy to do, but we’re currently providing a CoreOS image for testing with so you can just use that. You can find it by listing all images and grepping for CoreOS:

$ brightbox images list | grep CoreOS

 id         owner      type      created_on  status   size   name
 ---------------------------------------------------------------------------------------------------------
 img-9ogji  brightbox  official  2013-12-15  public   5442   CoreOS 147.0.1 (x86_64)

Build the servers

Before building the cluster, we need to generate a unique identifier for it, which is used by CoreOS to discover and identify nodes.

You can use any random string so we’ll use the uuid tool here to generate one:

$ TOKEN=`uuid`

$ echo $TOKEN
53cf11d4-3726-11e3-958f-939d4f7f9688

Then build three servers using the image, in the server group we created and specifying the token as the user data:

$ brightbox servers create -i 3 --type small --name "coreos" --user-data $TOKEN --server-groups grp-cdl6h img-9ogji

Creating 3 small (typ-8fych) servers with image CoreOS 94.0.0 (img-9ogji) in groups grp-cdl6h with 0.05k of user data

 id         status    type   zone   created_on  image_id   cloud_ip_ids  name  
--------------------------------------------------------------------------------
 srv-ko2sk  creating  small  gb1-a  2013-10-18  img-9ogji                coreos
 srv-vynng  creating  small  gb1-a  2013-10-18  img-9ogji                coreos
 srv-7tf5d  creating  small  gb1-a  2013-10-18  img-9ogji                coreos
--------------------------------------------------------------------------------

Accessing the cluster

Those servers should take just a minute to build and boot. They automatically install your Brightbox ssh key on bootup, so you can ssh in straight away as the core user.

If you’ve got ipv6 locally, you can ssh in directly:

$ ssh core@ipv6.srv-n8uak.gb1.brightbox.com
The authenticity of host 'ipv6.srv-n8uak.gb1.brightbox.com (2a02:1348:17c:423d:24:19ff:fef1:8f6)' can't be established.
RSA key fingerprint is 99:a5:13:60:07:5d:ac:eb:4b:f2:cb:c9:b2:ab:d7:21.
Are you sure you want to continue connecting (yes/no)? yes

Last login: Thu Oct 17 11:42:04 UTC 2013 from srv-4mhaz.gb1.brightbox.com on pts/0
   ______                ____  _____
  / ____/___  ________  / __ \/ ___/
 / /   / __ \/ ___/ _ \/ / / /\__ \
/ /___/ /_/ / /  /  __/ /_/ /___/ /
\____/\____/_/   \___/\____//____/
core@srv-n8uak:~$

If you don’t have ipv6, you’ll need to create and map a Cloud IP first.

Testing out etcd

The CoreOS guide takes you though playing with the etcd service:

$ curl -L http://127.0.0.1:4001/v1/keys/message -d value="Hello world"
{"action":"SET","key":"/message","prevValue":"Hello world","value":"Hello world","index":12}

$ curl -L http://127.0.0.1:4001/v1/keys/message
{"action":"GET","key":"/message","value":"Hello world","index":12}

Or you could kick off some docker containers:

$ docker run busybox /bin/echo hello world
Unable to find image     'busybox' (tag: latest) locally
Pulling repository busybox
e9aa60c60128: Download complete
hello world