A private container registry stores your container images within the premises of your data center. It's secure and quick even for 10GB+ images.

Harbor is an open-source registry for cloud-native platforms.

You can set up a fully-fledged private container registry with Harbor.

A container registry is an essential part of your CI/CD pipeline.

When deploying a Workload, the Kubernetes control plane schedules Pods into nodes in the cluster. Then, each node pulls the required container images from a container registry as specified by the Workload manifest.

DockerHub is a well-known container registry available as a service via the Internet. While a container registry as-a-service is convenient, there are certain use cases for a private container registry.

Why use a private container registry

A private container registry inside your data center is the best solution for these problems.

Networking requirements for a private container registry

You can deploy a private container registry with Harbor in either an on-premise data center or a VPC in a public cloud.

To pull the container images, Harbor must be accessible via HTTPS to all nodes in your Kubernetes clusters. You may have to configure routing and firewall rules in your data center to allow access to Harbor from the nodes.

If a particular node cannot access Harbor, the Pods scheduled in that node will fail to start.

What we are going to build

We are going to install Harbor on an Ubuntu 18.04 host. Then, we will build the number-crunch application on the development workstation, push the images to Harbor, and create a Kubernetes Deployment.

Harbor registry and K8s cluster Harbor registry and K8s cluster

Harbor is a containerized application and can be installed either on Docker or Kubernetes. Let’s use Docker for this setup.

To keep things simple we will not implement high availability here. But, you must definitely consider high availability in a production setup.

Here are the steps we have to go through.

  1. Prerequisites
  2. Create SSL certificates
  3. Install Harbor
  4. Create a project in Harbor
  5. Push images to Harbor
  6. Create Kubernetes Deployment

Let’s get started.

#1 Prerequisites

Set up networking

Make sure all nodes in your Kubernetes cluster can reach the Harbor host via HTTPS by configuring routing and firewall rules.

Install Docker

Install Docker and Docker Compose on Harbor host.

sudo apt update
sudo apt install docker
sudo apt install docker-compose

Install Docker Desktop on the Developer Workstation for building container images.

Configure DNS

We use registry.cloudqubes.com as the FQDN of Harbor. The developer workstation as well as the Kubernetes nodes must resolve this FQDN to the IP address of the Harbor host.

So, configure registry.cloudqubes.com in your local DNS server.

If you do not have a local DNS server, you can configure the hosts file in the developer workstation and in each node of the cluster to resolve registry.cloudqubes.com to the Harbor host IP address.

#2 Create SSL certificates

We need an SSL certificate to enable HTTPS access to Harbor.

We can either get a signed certificate from a CA or create a self-signed certificate. Let’s use a self-signed certificate for this setup.

We’ll use registry.cloudqubes.com as the FQDN of our Harbor host.

You can create these certificates on any Linux host.

Create the private key for the CA certificate.

openssl genrsa -out ca.key 4096

Create the CA certificate - valid for 10 years. If you continue to use this in production, make sure to renew it in 10 years from today.

openssl req -x509 -new -nodes -sha512 -days 3650 \
 -subj "/C=US/ST=Delaware/L=Lewes/O=CloudQubes/OU=IT/CN=registry.cloudqubes.com" \
 -key ca.key \
 -out ca.crt

Create private key.

openssl genrsa -out registry.cloudqubes.com.key 4096

Create certificate signing request.

openssl req -sha512 -new \
    -subj "/C=CN/ST=Beijing/L=Beijing/O=example/OU=Personal/CN=registry.cloudqubes.com" \
    -key registry.cloudqubes.com.key \
    -out registry.cloudqubes.com.csr

Create X509 v3 extension file.

cat > v3.ext <<-EOF
authorityKeyIdentifier=keyid,issuer
basicConstraints=CA:FALSE
keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names

[alt_names]
DNS.1=registry.cloudqubes.com
DNS.2=cloudqubes.com
DNS.3=registry
EOF

Create certificate for Harbor host.

openssl x509 -req -sha512 -days 3650 \
    -extfile v3.ext \
    -CA ca.crt -CAkey ca.key -CAcreateserial \
    -in registry.cloudqubes.com.csr \
    -out registry.cloudqubes.com.crt

Copy the certificates to Harbor host

Copy the server certificate and key to the certificate folder in Harbor host.

sudo cp registry.cloudqubes.com.crt /data/cert/
sudo cp registry.cloudqubes.com.key /data/cert/

Convert registry.cloudqubes.com.crt to .cert file.

openssl x509 -inform PEM -in registry.cloudqubes.com.crt -out registry.cloudqubes.com.cert

Copy the certificate file to Docker certificates folder.

cp registry.cloudqubes.com.cert /etc/docker/certs.d/registry.cloudqubes.com/
cp registry.cloudqubes.com.key /etc/docker/certs.d/registry.cloudqubes.com/
cp ca.crt /etc/docker/certs.d/registry.cloudqubes.com/

Restart Docker.

sudo systemctl restart docker

Copy the CA certificate to all Kubernetes nodes

Since we are using a self-signed certificate in Harbor we need to tell each node in the Kubernetes cluster to trust it. Copy the CA certificate ca.crt from the Harbor host to all nodes in the Kubernetes cluster.

Login to each node and run the following commands.

sudo cp ca.crt /usr/local/share/ca-certificates
sudo update-ca-certificates
sudo systemctl restart containerd.service

Remember to do the same for any new nodes you add to the cluster. If not, the Pods scheduled on the particular nodes will fail.

#3 Install Harbor

Harbor has two installation methods.

Download the offline installer to the development workstation from the Harbor releases page and copy it to the Harbor host.

Extract the installer.

tar xzvf harbor-offline-installer-v2.8.3.tgz 

The installer will be extracted to harbor directory in the current path. Go in and create harbor.yml by making a copy of harbor.yml.tmpl.

cd harbor
cp harbor.yml.tmpl harbor.yml

The harbor.yml sets the initial parameters for the Harbor installation.

Let’s update the certificate and private_key parameters to set the path to the certificate and key files we created.

# https related config
https:
  # https port for harbor, default is 443
  port: 443
  # The path of cert and key files for nginx
  certificate: /etc/docker/certs.d/registry.cloudqubes.com/registry.cloudqubes.com.cert
  private_key: /etc/docker/certs.d/registry.cloudqubes.com/registry.cloudqubes.com.key

Run the installation script.

sudo ./install.sh 

Check the running containers.

sudo docker container ls

Make sure all containers are up and running.

CONTAINER ID   IMAGE                                COMMAND                  CREATED      STATUS                             PORTS                                                                            NAMES
1f54cb0ae6d2   goharbor/nginx-photon:v2.8.3         "nginx -g 'daemon of…"   4 days ago   Up 10 seconds (health: starting)   0.0.0.0:80->8080/tcp, :::80->8080/tcp, 0.0.0.0:443->8443/tcp, :::443->8443/tcp   nginx
fa40611eb108   goharbor/harbor-jobservice:v2.8.3    "/harbor/entrypoint.…"   4 days ago   Restarting (2) 48 seconds ago                                                                                       harbor-jobservice
f7bd16f4d374   goharbor/harbor-core:v2.8.3          "/harbor/entrypoint.…"   4 days ago   Up 33 seconds (healthy)                                                                                             harbor-core
bc44f1a8f744   goharbor/harbor-registryctl:v2.8.3   "/home/harbor/start.…"   4 days ago   Up 10 seconds (health: starting)                                                                                    registryctl
7657237ed9e7   goharbor/harbor-db:v2.8.3            "/docker-entrypoint.…"   4 days ago   Up 10 seconds (health: starting)                                                                                    harbor-db
f2e8f5b6a88f   goharbor/harbor-portal:v2.8.3        "nginx -g 'daemon of…"   4 days ago   Up 11 minutes (healthy)                                                                                             harbor-portal
3ce34722713b   goharbor/registry-photon:v2.8.3      "/home/harbor/entryp…"   4 days ago   Up 10 seconds (health: starting)                                                                                    registry
d0980474a980   goharbor/redis-photon:v2.8.3         "redis-server /etc/r…"   4 days ago   Up 11 minutes (healthy)                                                                                             redis
303bd115d130   goharbor/harbor-log:v2.8.3           "/bin/sh -c /usr/loc…"   4 days ago   Up 11 minutes (healthy)            127.0.0.1:1514->10514/tcp                                                        harbor-log
ubuntu@k8s1:~/harbor$ history

If you happen to restart Docker Service for some reason, all the containers belonging to Harbor may not start. In such situations go to the installation directory and use docker-compose to start the containers again.

sudo docker-compose up -d

Login to Harbor web UI

Configure the hosts file in the development workstation to resolve registry.cloudqubes.com to the IP address of the Harbor host and go to https://registry.cloudqubes.com to log in to the Harbor UI.

Harbor creates an admin account at the installation with the password set in the harbor_admin_password directive in harbor.yml. Login to Harbor UI with this password.

#4 Create a project in Harbor

On the Harbor web UI home page, click on New Project.

Enter the name number-crunch, tick the checkbox Public, and click OK to create the project.

Harbor Web UI - Project list Harbor Web UI - Project list

Click on the project name number-crunch to access the project details.

number-crunch repositories number-crunch repositories

There are no repositories, as we have not yet published any container images to this project.

#5 Push images to Harbor

In the developer workstation, clone the repository number-crunch and build container images.

git clone git@github.com:cloudqubes/number-crunch.git
docker build -t registry.cloudqubes.com/number-crunch/number-crunch-app:1.0.0 .

Our image name is starting with registry.cloudqubes.com. This is the FQDN of the Harbor host. This name is required for Kubernetes to locate the container registry.

Login to Harbor container registry from Docker CLI in the developer workstation.

sudo docker login -u admin registry.cloudqubes.com

When prompted, type in the password of the Harbor admin user. Since we have not changed it, the password is the same as we used to login to the Harbor UI.

Push the image to Harbor.

sudo docker push registry.cloudqubes.com/number-crunch/number-crunch-app:1.0.0

#6 Create Kubernetes Deployment

Create a Kubernetes secret to store Harbor login information.

kubectl create secret docker-registry harbor-registry-secret --docker-server="https://registry.cloudqubes.com" --docker-username="admin" --docker-password="Harbor12345"

Create the manifest number-crunch.yml.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: number-crunch-app
spec:
  selector:
    matchLabels:
      app: number-crunch
  replicas: 2 
  template:
    metadata:
      labels:
        app: number-crunch
    spec:
      containers:
      - name: number-crunch
        image: registry.cloudqubes.com/number-crunch/number-crunch-app:1.0.0
        imagePullPolicy: Always
        ports:
        - containerPort: 8080
      imagePullSecrets:
      - name: harbor-registry

Note the image name starting with registry.cloudqubes.com which is the FQDN of our container registry.

Use kubectl to create the Deployment.

kubectl apply -f number-crunch.yml

Check whether all Pods are running.

kubectl get pods
NAME                                READY   STATUS    RESTARTS       AGE
number-crunch-app-5dc7b48bb-4pw7r   1/1     Running   0              118m
number-crunch-app-5dc7b48bb-85xql   1/1     Running   0              118m

If any node cannot pull images from Harbor, the Pods scheduled on that node will fail to start. You can use kubectl describe pod to check the reason for failure.

kubectl describe pod <pod-name>

If any Pod fails to start, one of these are likely to be the reason.

Troubleshooting along these points will lead you to a solution.

Harbor shows you the number of pulls for each image. This is also useful to ascertain whether Kubernetes can successfully pull images from this registry.

Number of pulls for a repository in Harbor project Number of Pulls

Wrapping up

If you have a good reason for a private container registry, Harbor is definitely for you.

It’s a CNCF graduated, open-source project. It’s easy to get started and includes all the features for a secure private registry.

So, give it a try in your VPC or data center.

And let me know if something goes wrong while you are setting up Harbor.

Post your problem in comments here or reach me via Twitter @cloudqubes for any help.