Libvirt Hostname Resolution

22 Dec 2019

I use Vagrant when testing new machines and experimenting locally with clusters, and since moving (mostly) to Linux, I have been using the LibVirt Plugin to create the virtual machines. Not only is it significantly faster than Hyper-V was on windows, but it also means I don’t need to use Oracle products, so it’s win-win really.

The only configuration challenge I have had with it is setting up VM hostname resolution, and as I forget how to do it each time, I figured I should write about it.


First I install the plugin so Vagrant can talk to Libvirt.

vagrant plugin install vagrant-libvirt

I also created a single vagrantfile with two virtual machines defined in it, so that I can check that the machines can resolve each other, as well as the host being able to resolve the guests.

Vagrant.configure("2") do |config| = "elastic/ubuntu-16.04-x86_64"

 config.vm.define "one" do |n1|
 n1.vm.hostname = "one"

 config.vm.define "two" do |n1|
 n1.vm.hostname = "two"

Once running vagrant up has finished (either with --provider libvirt or setting ` VAGRANT_DEFAULT_PROVIDER=libvirt`), connect to one of the machines, and try to ping the other:

[email protected]$ vagrant ssh one
[email protected]$ ping two
ping: unknown host two
[email protected]$ exit

Now that we can see they can’t resolve each other let’s move on to fixing it.

Custom Domain

The solution is to configure the libvirt network to have a domain name, and then to set the host machine to send requests for that domain to the virtual network.

First, I picked a domain. It doesn’t matter what it is, but I gather using .local will cause problems with other services, so instead, I picked $, which is in this case.

Vagrant-libvirt by default creates a network called vagrant-libvirt, so we can edit it to include the domain name configuration by running the following command:

virsh net-edit --network vagrant-libvirt

And adding the ` line to the xml which is displayed:

<network ipv6='yes'>
 <forward mode='nat'/>
 <bridge name='virbr1' stp='on' delay='0'/>
 <mac address='52:54:00:a0:ae:fd'/>
+ <domain name='' localOnly='yes'/>
 <ip address='' netmask=''>
 <range start='' end=''/>

To make the changes take effect, we need to destroy and re-create the network, so first I destroy the vagrant machines, then destroy and restart the network:

vagrant destroy -f
virsh net-destroy --network vagrant-libvirt
virsh net-start --network vagrant-libvirt

Finally, we can re-create the machines, and log in to one to check that they can resolve each other:

[email protected]$ vagrant up
[email protected]$ vagrant ssh one
[email protected]$ ping two
PING ( 56(84) bytes of data.
[email protected]$ exit

You can also check that the host can resolve the machine names when querying the virtual network’s DNS server:

[email protected]$ dig @ +short one

Host DNS Forwarding

The host cant talk to the machines by name still, so we need to tweak the host’s DNS, which means fighting with SystemD. Luckily, we only need to forward requests to a DNS server running on port 53 - if it was on another port then replacing systemd-resolved like my post on Consul DNS forwarding would be necessary.

Edit /etc/systemd/resolved.conf on the host, to add two lines which instruct it to send DNS requests for the domain picked earlier to the DNS server run by libvirt (dnsmasq):


Lastly, restart systemd-resolved for the changes to take effect:

systemctl restart systemd-resolved

Now we can resolve the guest machines by hostname at the domain we picked earlier:

[email protected]$ ping
PING ( 56(84) bytes of data.


Nomad Good, Kubernetes Bad

21 Nov 2019

I will update this post as I learn more (both positive and negative), and is here to be linked to when people ask me why I don’t like Kubernetes, and why I would pick Nomad in most situations if I chose to use an orchestrator at all.

TLDR: I don’t like complexity, and Kubernetes has more complexity than benefits.

Operational Complexity

Operating Nomad is very straight forward. There are very few moving parts, so the number of things which can go wrong is significantly reduced. No external dependencies are required to run it, and there is only one binary to use. You run 3-5 copies in Server mode to manage the cluster and as many as you want running in Client mode to do the actual work. You can add Consul if you want service discovery, but it’s optional. More on that later.

Compare this to operating a Kubernetes cluster. There are multiple Kubernetes orchestration projects, tools, and companies to get clusters up and running, which should be an indication of the level of complexity involved. Once you have the cluster set up, you need to keep it running. There are so many moving parts (Controller Manager, Scheduler, API Server, Etcd, Kubelets) that it quickly becomes a full-time job to keep the cluster up and running. Use a cloud service to run Kubernetes, and if you must use your own infrastructure, pay someone else to manage it. It’s cheaper in the long run. Trust me.


Nomad, being a single binary, is easy to deploy. If you want to use Terraform to create a cluster, Hashicorp provides modules for both AWS and Azure. Alternatively, you can do everything yourself, as it’s just keeping one binary running on hosts, and a bit of network/DNS config to get them talking to each other.

By comparison, Kubernetes has a multitude of tools to help you deploy a cluster. Still, while it gives you a lot of flexibility in choice, you also have to hope that the tool continues to exist and that there is enough community/company/documentation about that specific tool to help you when something goes wrong.

Upgrading The Cluster

Upgrading Nomad involves doing a rolling deployment of the Servers and Clients. If you are using the Hashicorp Terraform module, you re-apply the module with the new AMI ID to use, and then delete nodes (gracefully!) from the cluster and let the AutoScaleGroup take care of bringing new nodes up. If you need to revert to an older version of Nomad, you follow the same process.

When it comes to Kubernetes, please pay someone else to do it. It’s not a fun process. The process will differ depending on which cluster management tool you are using, and you also need to think about updates to etcd and managing state in the process. There is a nice long document on how to upgrade etcd.

Debugging a Cluster

As mentioned earlier, Nomad has a small number of moving parts. There are three ports involved (HTTP, RPC and Gossip), so as long as those ports are open and reachable, Nomad should be operable. Then you need to keep the Nomad agents alive. That’s pretty much it.

Where to start for Kubernetes? As many Kubernetes Failure Stories point out: it’s always DNS. Or etcd. Or Istio. Or networking. Or Kubelets. Or all of these.

Local Development

To run Nomad locally, you use the same binary as the production clusters, but in dev mode: nomad agent -dev. To get a local cluster, you can spin up some Vagrant boxes instead. I use my Hashibox Vagrant box to do this when I do conference talks and don’t trust the wifi to work.

To run Kubernetes locally to test things, you need to install/deploy MiniKube, K3S, etc. The downside to this approach is that the environment is significantly different to your real Kubernetes cluster, and you can end up where a deployment works in one, but not the other, which makes debugging issues much harder.

Features & Choice

Nomad is relatively light on built-in features, which allows you the choice of what features to add, and what implementations of the features to use. For example, it is pretty popular to use Consul for service discovery, but if you would rather use Eureka, or Zookeeper, or even etcd, that is fine, but you lose out on the seamless integration with Nomad that other Hashicorp tools have. Nomad also supports Plugins if you want to add support for your favourite tool.

By comparison, Kubernetes does everything, but like the phrase “Jack of all trades, master of none”, often you will have to supplement the inbuilt features. The downside to this is that you can’t switch off Kubernetes features you are not using, or don’t want. So if you add Vault for secret management, the Kubernetes Secrets are still available, and you have to be careful that people don’t use them accidentally. The same goes for all other features, such as Load Balancing, Feature Toggles, Service Discovery, DNS, etc.

Secret Management

Nomad doesn’t provide a Secret Management solution out of the box, but it does have seamless Vault integration, and you are also free to use any other Secrets As A Service tool you like. If you do choose Vault, you can either use it directly from your tasks or use Nomad’s integration to provide the secrets to your application. It can even send a signal (e.g. SIGINT etc.) to your process when the secrets need re-reading.

Kubernetes, on the other hand, provides “Secrets”. I put the word “secrets” in quotes because they are not secrets at all. The values are stored encoded in base64 in etcd, so anyone who has access to the etcd cluster has access to all the secrets. The official documentation suggests making sure only administrators have access to the etcd cluster to solve this. Oh, and if you can deploy a container to the same namespace as a secret, you can reveal it by writing it to stdout.

Kubernetes secrets are not secret, just “slightly obscured.”

If you want real Secrets, you will almost certainly use Vault. You can either run it inside or outside of Kubernetes, and either use it directly from containers via it’s HTTPS API or use it to populate Kubernetes Secrets. I’d avoid populating Kubernetes Secrets if I were you.


If Nomad breaks, you can either use community support or if you are using the Enterprise version, you have Hashicorp’s support.

When Kubernetes breaks, you can either use community support or find and buy support from a Kubernetes management company.

The main difference here is “when Kubernetes breaks” vs “if Nomad breaks”. The level of complexity in Kubernetes makes it far more likely to break, and that much harder to debug.

Creating a Vault instance with a TLS Consul Cluster

06 Oct 2019

So we want to set up a Vault instance, and have it’s storage be a TLS based Consul cluster. The problem is that the Consul cluster needs Vault to create the certificates for TLS, which is quite the catch-22. Luckily for us, quite easy to solve:

  1. Start a temporary Vault instance as an intermediate ca
  2. Launch Consul cluster, using Vault to generate certificates
  3. Destroy temporary Vault instance
  4. Start a permanent Vault instance, with Consul as the store
  5. Reprovision the Consul cluster with certificates from the new Vault instance

Sequence diagram of the previous numbered list

There is a repository on Github with all the scripts used, and a few more details on some options.


The Host machine needs the following software available in your PATH:

You have a TLS Certificate you can use to create an intermediate CA with. See this blog post for How to create a local CA


The script will do all of this for you, but an explanation of the steps is below:

  1. Start a Temporary Vault instance

     echo '
     storage "inmem" {}
     listener "tcp" {
       address = ""
       tls_disable = 1
     }' > "vault/temp_vault.hcl"
     vault server -config="vault/temp_vault.hcl" &
     echo "$!" >
     export VAULT_TOKEN=$(./ | tail -n 1)
  2. Generate a Vault token for the Consul machines to use to authenticate with Vault

     export CONSUL_VAULT_TOKEN=$(vault write -field=token -force auth/token/create)
  3. Launch 3 Consul nodes (uses the CONSUL_VAULT_TOKEN variable)

     vagrant up

    The vagrantfile just declares 3 identical machines:

     Vagrant.configure(2) do |config| = "pondidum/hashibox"
       config.vm.provision "consul",
         type: "shell",
         path: "./",
         env: {
       config.vm.define "c1" do |c1|
         c1.vm.hostname = "consul1"
       config.vm.define "c2" do |c2|
         c2.vm.hostname = "consul2"
       config.vm.define "c3" do |c3|
         c3.vm.hostname = "consul3"

    The provisioning script just reads a certificate from Vault, and writes out pretty much the same configuration as in the last post on creating a TLS enabled Consul Cluster, but you can view it in the repository for this demo too.

  4. Create a local Consul server to communicate with the cluster:


    This is done so that the Vault instance can always communicate with the Consul cluster, no matter which Consul node we are reprovisioning later. In a production environment, you would have this Consul server running on each machine that Vault is running on.

  5. Stop the temporary Vault instance now that all nodes have a certificate

    kill $(cat
  6. Start the persistent Vault instance, using the local Consul agent

     echo '
     storage "consul" {
       address = "localhost:8501"
       scheme = "https"
     listener "tcp" {
       address = ""
       tls_disable = 1
     }' > "$config_dir/persistent_vault.hcl"
     vault server -config="$config_dir/persistent_vault.hcl" > /dev/null &
     echo "$!" >
     export VAULT_TOKEN=$(./ | tail -n 1)
  7. Generate a new Vault token for the Consul machines to use to authenticate with Vault (same as step 2)

     export CONSUL_VAULT_TOKEN=$(vault write -field=token -force auth/token/create)
  8. Reprovision the Consul nodes with new certificates

     vagrant provision c1 --provision-with consul
     vagrant provision c2 --provision-with consul
     vagrant provision c3 --provision-with consul
  9. Profit

    To clean up the host’s copy of Vault and Consul, you can run this:

     kill $(cat
     kill $(cat

Summary & Further Actions

Luckily, this is the kind of thing that should only need doing once (or once per isolated environment). When running in a real environment, you will also want to set up:

  • ACL in Consul which locks down the KV storage Vault uses to only be visible/writeable by Vault
  • Provisioning the VAULT_TOKEN to the machines in a secure fashion
  • Periodic refresh of the Certificates uses in the Consul cluster

Consul DNS Fowarding in Ubuntu, revisited

24 Sep 2019

I was recently using my Hashibox for a test, and I noticed the DNS resolution didn’t seem to work. This was a bit worrying, as I have written about how to do DNS resolution with Consul forwarding in Ubuntu, and apparently something is wrong with how I do it. Interestingly, the Alpine version works fine, so it appears there is something not quite working with how I am configuring Systemd-resolved.

So this post is how I figured out what was wrong, and how to do DNS resolution with Consul forwarding on Ubuntu properly!

The Problem

If Consul is running on the host, I can only resolve .consul domains, and if Consul is not running, I can resolve anything else. Clearly I have configured something wrong!

To summarise, I want to be able to resolve 3 kinds of address:

  • *.consul addresses should be handled by the local Consul instance
  • $ should be handled by the Hyper-V DNS server (running on the Host machine)
  • public DNS should be resolved properly


To make sure that hostname resolution even works by default, I create a blank Ubuntu box in Hyper-V, using Vagrant.

Vagrant.configure(2) do |config| = "bento/ubuntu-16.04"
  config.vm.hostname = "test"

I set the hostname so that I can test that dns resolution works from the host machine to the guest machines too. I next bring up the machine, SSH into it, and try to dig my hostmachine’s DNS name (

> vagrant up
> vagrant ssh
> dig

; <<>> DiG 9.10.3-P4-Ubuntu <<>>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12333
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;            IN      A

;; ANSWER SECTION:     0       IN      A

;; Query time: 0 msec
;; WHEN: Mon Sep 23 21:57:26 UTC 2019
;; MSG SIZE  rcvd: 70

> exit
> vagrant destroy -f

As you can see, the host machine’s DNS server responds with the right address. Now that I know that this should work, we can tweak the Vagrantfile to start an instance of my Hashibox:

Vagrant.configure(2) do |config| = "pondidum/hashibox"
  config.vm.hostname = "test"

When I run the same command sin this box, I get a slighty different response:

; <<>> DiG 9.10.3-P4-Ubuntu <<>>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 57216
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

; EDNS: version: 0, flags:; udp: 4096
;            IN      A

consul.                 0       IN      SOA     ns.consul. hostmaster.consul. 1569276784 3600 600 86400 0

;; Query time: 1 msec
;; WHEN: Mon Sep 23 22:13:04 UTC 2019
;; MSG SIZE  rcvd: 103

As intended, the DNS server on localhost responded…but it looks like Consul answered, not the inbuilt dns server (systemd-resolved), as I intended.

The reason for this is that I am running Consul’s DNS endpoint on 8600, and Systemd-Resolved cannot send requests to anything other than port 53, so I use iptables to redirect the traffic from port 53 to 8600, which means any local use of DNS will always be sent to Consul.

The reason it works when Consul is not running is that we have both specified as a nameserver, and a fallback set to be the eth0’s Gateway, so when Consul doesn’t respond, the request hits the default DNS instead.

The Solution: Dnsmasq.

Basically, stop using systemd-resolved and use something that has a more flexible configuration. Enter Dnsmasq.

Starting from the blank Ubuntu box, I install dnsmasq, and disable systemd-resolved. Doing this might prevent any DNS resolutio working for a while…

sudo apt-get install -yq dnsmasq
sudo systemctl disable systemd-resolved.service

If you would rather not disable systemd-resolved entirely, you can use these two lines instead to just switch off the local DNS stub:

echo "DNSStubListener=no" | sudo tee --append /etc/systemd/resolved.conf
sudo systemctl restart systemd-resolved

Next I update /etc/resolv.conf to not be managed by Systemd, and point to where dnsmasq will be running:

sudo rm /etc/resolv.conf
echo "nameserver" | sudo tee /etc/resolv.conf

The reason for deleting the file is that it was symlinked to the Systemd-Resolved managed file, so that link needed to be broken first to prevent Systemd interfering.

Lastly a minimal configuration for dnsmasq:

echo '
' | sudo tee /etc/dnsmasq.d/default

sudo systemctl restart dnsmasq

This config does a few things, the two most important lines are:

  • resolv-file=/var/run/dnsmasq/resolv.conf which is pointing to the default resolv.conf written by dnsmasq. This file contains the default nameserver supplied by the default network connection, and I want to use this as a fallback for anything dnsmasq cannot resolve directly (which will be everything, except .consul). In my case, the content of this file is just nameserver

  • server=/consul/ specifies that any address ending in .consul should be forwarded to Consul, running at on port 8600. No more iptables rules!


Now that I have a (probably) working DNS system, let’s look at testing it properly this time. There are 3 kinds of address I want to test:

  • Consul resolution, e.g. consul.service.consul should return the current Consul instance address.
  • Hostname resolution, e.g. should resolve to the machine hosting the VM.
  • Public resolution, e.g. should resolve to…reddit.

I also want to test that the latter two cases work when Consul is not running too.

So let’s write a simple script to make sure these all work. This way I can reuse the same script on other machines, and also with other VM providers to check DNS works as it should. The entire script is here:


consul agent -dev -client -bind '{{ GetInterfaceIP "eth0" }}' > /dev/null &
sleep 1

consul_ip=$(dig consul.service.consul +short)
self_ip=$(dig $HOSTNAME.$local_domain +short | tail -n 1)
host_ip=$(dig $host_machine.$local_domain +short | tail -n 1)
reddit_ip=$(dig +short | tail -n 1)

kill %1

[ "$consul_ip" == "" ] && echo "Didn't get consul ip" >&2 && exit 1
[ "$self_ip" == "" ] && echo "Didn't get self ip" >&2 && exit 1
[ "$host_ip" == "" ] && echo "Didn't get host ip" >&2 && exit 1
[ "$reddit_ip" == "" ] && echo "Didn't get reddit ip" >&2 && exit 1

echo "==> Consul Running: Success!"

consul_ip=$(dig consul.service.consul +short | tail -n 1)
self_ip=$(dig $HOSTNAME.$local_domain +short | tail -n 1)
host_ip=$(dig $host_machine.$local_domain +short | tail -n 1)
reddit_ip=$(dig +short | tail -n 1)

[[ "$consul_ip" != *";; connection timed out;"* ]] && echo "Got a consul ip ($consul_ip)" >&2 && exit 1
[ "$self_ip" == "" ] && echo "Didn't get self ip" >&2 && exit 1
[ "$host_ip" == "" ] && echo "Didn't get host ip" >&2 && exit 1
[ "$reddit_ip" == "" ] && echo "Didn't get reddit ip" >&2 && exit 1

echo "==> Consul Stopped: Success!"

exit 0

What this does is:

  1. Read two command line arguments, or use defaults if not specified
  2. Start Consul as a background job
  3. Query 4 domains, storing the results
  4. Stop Consul (kill %1)
  5. Check an IP address came back for each domain
  6. Query the same 4 domains, storing the results
  7. Check that a timeout was received for consul.service.consul
  8. Check an IP address came back for the other domains

To further prove that dnsmasq is forwarding requests correctly, I can include two more lines to /etc/dnsmasq.d/default to enable logging, and restart dnsmasq

echo "log-queries" | sudo tee /etc/dnsmasq.d/default
echo "log-facility=/var/log/dnsmasq.log" | sudo tee /etc/dnsmasq.d/default
sudo systemctl restart dnsmasq
dig consul.service.consul

Now I can view the log file and check that it received the DNS query and did the right thing. In this case, it recieved the consul.service.consul query, and forwarded it to the local Consul instance:

Sep 24 06:30:50 dnsmasq[13635]: query[A] consul.service.consul from
Sep 24 06:30:50 dnsmasq[13635]: forwarded consul.service.consul to
Sep 24 06:30:50 dnsmasq[13635]: reply consul.service.consul is

I don’t tend to keep DNS logging on in my Hashibox as the log files can grow very quickly.

Wrapping Up

Now that I have proven my DNS resolution works (I think), I have rolled it back into my Hashibox, and can now use machine names for setting up clusters, rather than having to specify IP addresses initially.

Creating a TLS enabled Consul cluster

14 Sep 2019

This post is going to go through how to set up a Consul cluster to communicate over TLS. I will be using Vagrant to create three machines locally, which will form my cluster, and in the provisioning step will use Vault to generate the certificates needed.

How to securely communicate with Vault to get the TLS certificates is out of scope for this post.

Host Configuration

Unless you already have Vault running somewhere on your network, or have another mechanism to generate TLS certificates for each machine, you’ll need to start and configure Vault on the Host machine. I am using my Vault Dev Intermediate CA script from my previous post.

To set this up, all I need to do is run this on the host machine, which starts Vault in a docker container, and configures it as an intermediate certificate authority:


I also have DNS on my network setup for the domain so will be using that to test with.

Consul Machine Configuration

The Vagrantfile is very minimal - I am using my Hashibox (be aware the libvirt provider for this might not work, for some reason vagrant package with libvirt produces a non-bootable box).

Vagrant.configure(2) do |config| = "pondidum/hashibox"
  config.vm.provision "consul", type: "shell", path: "./"

  config.vm.define "c1" do |c1|
    c1.vm.hostname = "consul1"

  config.vm.define "c2" do |c2|
    c2.vm.hostname = "consul2"

  config.vm.define "c3" do |c3|
    c3.vm.hostname = "consul3"

The hashibox script already has all the tools we’ll need installed already: Consul, Vault, and jq.

First up, we request a certificate from Vault to use for Consul - How you get this certificate in a secure manner in a production environment is up to you. There is a catch-22 here for me, in that in a production environment I use Vault with Consul as it’s backing store…but Consul needs Vault to start! I’ll go over how I get around this in a future post.

export VAULT_ADDR=""
export VAULT_TOKEN="vault"

response=$(vault write pki/issue/cert -format=json common_name=$ alt_names="server.dc1.consul")

The first thing to note is that we have specified an alt_names for the certificate - you must have a SAN of server.$DC.$DOMAIN so either server.dc1.consul or, and the server prefix is required!.

Next, we need to take all the certificates from the response and write them to the filesystem.

mkdir -p "$config_dir/ca"

for (( i=0; i<$(echo "$response" | jq '.data.ca_chain | length'); i++ )); do
  cert=$(echo "$response" | jq -r ".data.ca_chain[$i]")
  name=$(echo "$cert" | openssl x509 -noout -subject -nameopt multiline | sed -n 's/ *commonName *= //p' | sed 's/\s//g')

  echo "$cert" > "$config_dir/ca/$name.pem"

echo "$response" | jq -r .data.private_key > $config_dir/consul.key
echo "$response" | jq -r .data.certificate > $config_dir/consul.crt
echo "$response" | jq -r .data.issuing_ca >> $config_dir/consul.crt

The for loop iterates through all of the certificates returned in the ca_chain and writes them into a ca directory. We use openssl to get the name of the certificate, so the files are named nicely!

Finally, it writes the private_key for the node’s certificate to consul.key, and both the certificate and issuing_ca to the consul.crt file.

Now for the consul.json. To setup a secure cluster, first of all we need to add the certificate configuration, pointing to the files we wrote earlier:

"ca_path": "$config_dir/ca/",
"cert_file": "$config_dir/consul.crt",
"key_file": "$config_dir/consul.key",

We will also disable the HTTP port, and enable the HTTPS port:

"ports": {
    "http": -1,
    "https": 8501

Finally, we need to add some security settings. First is encrypt, which sets that the key that all Consul nodes will use to encrypt their communications. It must match on all nodes. The easiest way to generate this is just run consul keygen and use the value that produces.

  • "encrypt": "oNMJiPZRlaP8RnQiQo9p8MMK5RSJ+dXA2u+GjFm1qx8=":

    The key the cluster will use to encrypt all it’s traffic. It must be the same on all nodes, and the easiest way to generate the value is to use the output of consul keygen.

  • "verify_outgoing": true:

    All the traffic leaving this node will be encrypted with the TLS certificates. However, the node will still accept non-TLS traffic.

  • "verify_incoming_rpc": true:

    All the gossip traffic arriving at this node must be signed with an authority in the ca_path.

  • "verify_incoming_https": false:

    We are going to use the Consul Web UI, so we want to allow traffic to hit the API without a client certificate. If you are using the UI from a non-server node, you can set this to true.

  • "verify_server_hostname": true:

    Set Consul to verify outgoing connections have a hostname in the format of server.<datacenter>.<domain>. From the docs: “This setting is critical to prevent a compromised client from being restarted as a server and having all cluster state including all ACL tokens and Connect CA root keys replicated to it”

The complete config we will use is listed here:

cat <<-EOF
    "bootstrap_expect": 3,
    "client_addr": "",
    "data_dir": "/var/consul",
    "leave_on_terminate": true,
    "rejoin_after_leave": true,
    "retry_join": ["consul1", "consul2", "consul3"],
    "server": true,
    "ui": true,
    "encrypt": "oNMJiPZRlaP8RnQiQo9p8MMK5RSJ+dXA2u+GjFm1qx8=",
    "verify_incoming_rpc": true,
    "verify_incoming_https": false,
    "verify_outgoing": true,
    "verify_server_hostname": true,
    "ca_path": "$config_dir/ca/",
    "cert_file": "$config_dir/consul.crt",
    "key_file": "$config_dir/consul.key",
    "ports": {
        "http": -1,
        "https": 8501
) | sudo tee $config_dir/consul.json

Lastly, we’ll make a systemd service unit to start consul:

cat <<-EOF
Description=consul agent

ExecStart=/usr/bin/consul agent -config-file=$config_dir/consul.json -bind '{{ GetInterfaceIP "eth0" }}'
ExecReload=/bin/kill -HUP $MAINPID

) | sudo tee /etc/systemd/system/consul.service

sudo systemctl daemon-reload
sudo systemctl enable consul.service
sudo systemctl start consul

As the machines we are starting also have docker networks (and potentially others), our startup line specifies to bind to the eth0 network, using a Consul Template.


First, we need to run our intermediate CA, then provision our three machines:

vagrant up

After a few moments, you should be able to curl the consul ui (curl or open in your browser.

Note, however, the if your root CA is self-signed, like mine is, some browsers (such as FireFox) won’t trust it, as they won’t use your machine’s Trusted Certificate Store, but their own in built store. You can either accept the warning or add your root certificate to the browser’s store.


Now that we have our cluster seemingly running with TLS, what happens if we try to connect a Consul client without TLS to it? On the host machine, I just run a single node, and tell it to connect to one of the cluster nodes:

consul agent \
  -join \
  -bind '{{ GetInterfaceIP "eth0" }}' \
  -data-dir /tmp/consul

The result of this is a refusal to connect, as the cluster has TLS configured, but this instance does not:

==> Starting Consul agent...
==> Log data will now stream in as it occurs:
==> Joining cluster...
==> 1 error occurred:
  * Failed to join Remote state is encrypted and encryption is not configured


In the next post, I’ll go through how we can set up a Vault cluster which stores its data in Consul, but also provision that same Consul cluster with certificates from the Vault instance!