Installing and Using Nexus Repository for Artifact Storage

In software development, "artifact" is a component of a developed software product. Artifacts include executable and binary files, software packages, and more.

As the product's architecture and functionality increase, the number of artifacts grows exponentially, and you need a reliable storage solution that can manage large volumes of artifacts efficiently. 

One such solution is Nexus Repository by Sonatype. 

Nexus supports over 15 artifact formats, including APT, Docker, Go, Helm, Maven, npm, PyPi, and more. 

There are two versions of Nexus Repository:

• Free version – Includes essential repository management features.
• Commercial version – Offers customer support and a broader range of supported artifact types.

In this guide, we will install the free version of Nexus Repository.

Prerequisites

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You can install Nexus Repository on a Linux, Windows, or MacOS machine.

In this guide, we will use a Hostman cloud server running Ubuntu.

The server must meet the following minimum requirements:

• 4-core CPU. 8-core or higher is recommended.
• 8 GB RAM 
• 50 GB of free disk space (excluding OS and other installed software). If there is insufficient space, Nexus will not start.

The official Sonatype website provides recommended system requirements based on the number of repositories and stored artifacts.

Installing Nexus Repository

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Step 1: Install Java

First, update the package list:

sudo apt update

Then, install Java 8 using OpenJDK:

sudo apt -y install openjdk-8-jre-headless

After installation, verify Java's version:

java -version

If you have multiple Java versions installed, switch to Java 8:

sudo update-alternatives --config java

Select the correct version using the TAB key and confirm with Enter.

Step 2: Download and Extract Nexus

We will install Nexus in the /opt directory.

Download the latest Nexus archive:

sudo wget https://download.sonatype.com/nexus/3/latest-unix.tar.gz

Extract the archive to /opt:

sudo tar -zxvf latest-unix.tar.gz -C /opt

Rename the extracted directory (for easier management):

sudo mv /opt/nexus-3.61.0-02 /opt/nexus

Make sure to specify the correct version number in your case. 

Step 3: Create a Dedicated User for Nexus

Create a new user named nexus:

sudo adduser nexus

Disable direct login for this user:

sudo usermod nexus -s

Set the correct ownership for Nexus directories:

sudo chown -R nexus:nexus /opt/nexus /opt/sonatype-work

Step 4: Configure Nexus

Edit the Nexus configuration file:

sudo nano /opt/nexus/bin/nexus.rc

Uncomment (remove #) and set the user as nexus:

run_as_user="nexus"

Save and exit the file.

Step 5: Create a Systemd Service for Nexus

Create a new service file:

sudo nano /etc/systemd/system/nexus.service

Add the following content:

[Unit]
Description=Nexus Repository Manager
After=network.target

[Service]
Type=forking
LimitNOFILE=65536
ExecStart=/opt/nexus/bin/nexus start
ExecStop=/opt/nexus/bin/nexus stop
User=nexus
Restart=on-abort

[Install]
WantedBy=multi-user.target

Save and exit the file.

Step 6: Start and Enable Nexus

Start Nexus:

sudo systemctl start nexus

Check Nexus status:

systemctl status nexus

If the status is active, Nexus is running successfully.

Enable Nexus to start on boot:

sudo systemctl enable nexus

Step 7: Verify Nexus Startup

Nexus takes 2-3 minutes to fully start. To check the logs:

tail -f /opt/sonatype-work/nexus3/log/nexus.log

Once you see:

Started Sonatype Nexus OSS

Nexus is ready.

By default, the Nexus web interface is accessible on port 8081:

http://your-server-ip:8081

Initial Setup of Nexus Repository

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Step 1: Log into Nexus

1. Open the Nexus web interface.
2. Click the Sign in button (top-right corner).
3. Retrieve the default admin password by running:

cat /opt/sonatype-work/nexus3/admin.password

4. Use this password to log in as admin.

Step 2: Initial Configuration

1. Set a new password for the admin user.

2. Enable or disable anonymous access:
   • Enabled: Any user with the repository URL can browse/download artifacts without authentication.
   • Disabled: Authentication (login/password) is required.

Nexus is now ready to use.

Creating a Docker Repository in Nexus

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Step 1: Create a Docker Repository

1. Log in as admin.
2. Go to Server Administration and Configuration (gear icon).

3. In the left menu, select Repositories.
4. Click Create repository.
5. Choose docker (hosted).

Step 2: Configure the Repository

Nexus supports three types of repositories:

• Hosted: Stores artifacts directly in Nexus.
• Proxy: Fetches artifacts from remote repositories (e.g., APT).
• Group: Combines multiple repositories into one unified endpoint.

For a Docker repository:

1. Set a repository name, e.g., docker-images.
2. Enable HTTP access (check the box).
3. Assign a port number (e.g., 8083).
4. Save the settings.

Step 3: Configure Docker to Work with Nexus

By default, Docker does not allow HTTP connections. To enable HTTP access:

1. Edit or create the Docker daemon configuration file:

sudo nano /etc/docker/daemon.json

2. Add the following configuration:

{
  "insecure-registries": ["166.1.227.189:8083"]
}

(Replace 166.1.227.189:8083 with your Nexus server IP and port.)

3. Save and exit the file.

4. Restart the Docker service:

sudo systemctl restart docker

Step 4: Push a Docker Image to Nexus

1. Log in to Nexus via Docker:

docker login 166.1.227.189:8083

You can use the admin username and the password you set earlier.

2. Tag an image (e.g., alpine):

docker tag alpine:latest 166.1.227.189:8083/alpine-test

3. Verify the new tag:

docker images

4. Push the image to Nexus:

docker push 166.1.227.189:8083/alpine-test

5. Confirm the upload:

• • Open the Nexus web interface.
  • Go to the docker-images repository.
  • The alpine-test image should be listed.

Your Nexus repository is now set up for Docker image storage!

HTTPS Configuration

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The correct approach when working with Docker repositories is to use the HTTPS protocol. To configure HTTPS in Nexus, follow these steps:

1. Navigate to the /opt/nexus/etc/ssl directory:

cd /opt/nexus/etc/ssl

2. Use keytool to generate a self-signed certificate:

sudo keytool -genkeypair -keystore keystore.jks -storepass test12345 -keypass test12345 -alias jetty -keyalg RSA -keysize 2048 -validity 1000 -dname "CN=*.${NEXUS_DOMAIN}, OU=test, O=test1, L=Unspecified, ST=Unspecified, C=RU" -ext "SAN=DNS:nexus-repo.com,IP:166.1.227.189" -ext "BC=ca:true"

Replace the following values with your own:

• -keystore keystore.jks — Name of the file where the key will be stored, using the .jks format.
• -storepass test12345 — Password for accessing the key store.
• -keypass test12345 — Password for accessing the private key.
• -ext "SAN=DNS:nexus-repo.com,IP:166.1.227.189" — Specifies your Nexus server's domain name and IP address.

If a local domain is used, it must be added to the /etc/hosts file (for Linux) or C:\Windows\System32\drivers\etc\hosts in Windows.

3. Next, extract the server certificate from the generated keystore.jks file using the following command:

sudo keytool -export -alias jetty -keystore keystore.jks -rfc -file nexus.cert

The output will be a certificate file named nexus.cert.

4. Now, edit the Nexus configuration file nexus-default.properties located in /opt/nexus/etc:

sudo nano /opt/nexus/etc/nexus-default.properties

5. Find the section with the comment # Jetty section, and add the following parameter:

application-port-ssl=8443

This specifies the port where HTTPS will be available.

6. In the same section, add this line:

nexus-args=${jetty.etc}/jetty.xml,${jetty.etc}/jetty-http.xml,${jetty.etc}/jetty-https.xml,${jetty.etc}/jetty-requestlog.xml

7. Next, edit the jetty-https.xml file located in /opt/nexus/etc/jetty:

sudo nano /opt/nexus/etc/jetty/jetty-https.xml

• • Locate the block named sslContextFactory.
  • In the fields KeyStorePassword, KeyManagerPassword, TrustStorePassword, enter the password used during certificate generation. In this example, the password is test12345.
  • In the parameters KeyStorePath and TrustStorePath, specify the name of the generated certificate.

8. After making these changes, restart the Nexus service:

sudo systemctl restart nexus

Installing the Certificate on Linux

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In Linux, we must install the certificate at the OS level. Otherwise, when trying to authenticate to the repository using the docker login command, the following error may occur:

x509: certificate signed by unknown authority

To install the certificate on Ubuntu/Debian, follow these steps:

1. Install the ca-certificates package:

sudo apt -y install ca-certificates

2. The certificate must be in .crt format, as other formats are not supported. Since the certificate was generated as .cert, rename it to .crt:

sudo mv nexus.cert nexus.crt

3. Copy the certificate to /usr/local/share/ca-certificates:

sudo cp nexus.crt /usr/local/share/ca-certificates

4. Install the certificate using the following command:

sudo update-ca-certificates

Configuring HTTPS in the Nexus Repository

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To configure HTTPS in the repository:

1. Open the Nexus web interface and log in as an administrator.
2. Navigate to the Server Administration and Configuration section (gear icon).
3. In the left menu, select Repositories, find the required repository, check the box next to HTTPS, and specify a port that is not already in use on the server, such as 8344.

1. 4 Save the changes.
2. On the server, run the docker login command, specifying the repository address and HTTPS port:

docker login nexus-repo.com:8344

You can log in using the admin account.

Pushing an Image to the Repository

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To test pushing an image, let's use nginx:

1. Assign a tag to the image. The format for Docker image tags is as follows:

image:tag registry_address:repository_port/image_name

Example:

docker tag nginx:latest nexus-repo.com:8344/nginx-test

2. Verify that the new image exists:

docker images

3. Push the image to the repository:

docker push nexus-repo.com:8344/nginx-test

4. Open the Nexus web interface, navigate to the repository, and confirm that the image was successfully uploaded.

Conclusion

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Nexus Repository is an excellent solution for storing and managing artifacts. Supporting a wide range of artifact formats, it is suitable for both small development teams and larger enterprises.