For enquiries call:



HomeBlogDevOpsDocker Secrets - A Detailed Beginners Guide

Docker Secrets - A Detailed Beginners Guide

05th Sep, 2023
view count loader
Read it in
9 Mins
In this article
    Docker Secrets - A Detailed Beginners Guide

    Even if you've used Docker before for smaller or locally produced applications, it can be difficult to use for more sophisticated tasks. This is especially true when it comes to secret management and sharing, which are aspects that are sometimes disregarded when working with containerized apps.  There is no standard method for getting and managing secrets in containers, resulting in haphazard or ineffective solutions better suited to more static Docker secrets environment variables. Docker secrets, fortunately, are a terrific solution provided by the Docker community. 

    System administrators and developers can both gain from using Docker. To use Docker, consider the following factors: 

    • Docker enables hassle-free software installation and operation without concern for setup or dependencies. 
    • To avoid machine issues, developers utilize Docker. In order to run and manage apps in isolated containers with higher computing densities, operators utilize Docker. 
    • To deploy new application features more quickly and securely, businesses utilize Docker to build secure agile software delivery pipelines.  
    • Docker is a terrific platform for development in addition to being used for deployment, so we can effectively raise client happiness. 

    You’ll learn how to use Docker secrets in your development workflow in this blog. If you want to dig deep into DevOps, you can go through thicourse on DevOps. 

    What Are Docker Secrets?  

    Docker secrets are offered by Docker as part of its secrets management service. A secret in Docker is any record that should not be saved unencrypted in simple textual content files, such as passwords, SSH non-public credentials, certificates, or API keys. Docker secrets streamline the securing of this information. 

    Docker Architecture  

    The Docker client, Docker host, and Docker Registry are the three primary components of the Docker client-server architecture. 

    1. Docker Client  

    Commands and REST APIs are utilized by the Docker consumer to talk with the Docker daemon (server). When a consumer makes use of the Docker consumer terminal to run a Docker command, the instructions are added to the Docker daemon through the consumer terminal. The Docker daemon receives these directions from the secrets Docker compose consumer in the form of instructions and REST API queries. 

    The commands below are executed using the Docker client's Command-Line Interface (CLI): 

    • docker run secrets 
    • docker build secrets 
    • docker pull 

    2. Docker Host

    The Docker host is a platform for executing and running apps. The Docker storage, networks, containers, images, and daemon are all included in this package. 

    3. Docker Registry 

    The Docker Registry is the place where Docker images are managed and stored. In Docker, there are two types of registries: private registry and Docker Hub. 

    You can learn more about Docker at KnowledgeHut to find more information regarding Docker certification and courses. 

    Docker Objects

    Docker Images

    Docker images are binary templates that are read-only and are used to make Docker containers. They use a private container registry for internal sharing and a public container registry for external sharing. 

    Docker Containers 

    Containers are Docker's structural units, and they are used to keep the complete bundle required to run an application. Containers have the advantage of requiring extraordinarily few resources. 

    Docker Features 

    1. Security Administration: We can pick which secrets to grant services access to by storing them in the swarm itself. It contains certain crucial engine instructions, such as ones for secret creation and inspection. 
    2. Swarm: A swarm acts as a clustering and scheduling application for Docker containers. Swarm mode's front end, the Docker API, allows us to manipulate swarms using a variety of tools. Controlling a group of Docker hosts as a single virtual host also helps. The ability to self-organize a group of engines enables pluggable backends. A self-organizing group of engines enables pluggable backends. 
    3. Simple and Quick Configuration: This is a crucial aspect of Docker that makes it simpler and quicker for us to configure the system. We can deploy our code with less work and time. The needs of the infrastructure and the environment of the application are no longer connected because Docker may be utilized in a wide range of contexts. 
    4. Increasing Output: By facilitating technical configuration and quick application deployment, Docker undoubtedly increases productivity. Docker can reduce the resources required while also assisting in isolating and running applications. 
    5. Mesh Routing: It sends inbound requests for open ports on accessible nodes to running containers. Even if there are no tasks running on a node, this functionality makes it possible to connect. 

    How to Set UDocker [Step-by-Step]  

    Your operating system will determine how Docker is installed. However, it's straightforward everywhere. 

    All three major operating systems—macOS, Windows, and Linux—run Docker smoothly. We'll begin with installation on macOS because that is the simplest of the three. 

    1. Installing Docker on macOS   

    All you have to do to download Docker on a Mac is go to the official download page and select the Download for Mac (stable) option. 

    A standard-looking Apple Disk Image file with the application inside will be delivered to you. You only need to drag the file into your Applications directory. 

    By just double-clicking the application icon, Docker can be launched. The Docker symbol will show up on your menu bar as soon as the application launches.  

    To check that the installation was successful, launch the terminal and type docker —version and docker-compose —version. 

    2. Installing Docker on Windows   

    With just a few extra steps, the process is nearly identical on Windows. The installation procedure is as follows: 

    1. For assistance in installing WSL2 on Windows 10, visit this page and adhere to the instructions. 
    2. Next, access the official download website and select Download for Windows (stable). 
    3. The installer should be double-clicked, and the installation should proceed with the default settings. 

    Start Docker Desktop after it has finished installing, either from your desktop or the start menu. Your taskbar ought to contain the Docker icon. 

    Now, launch Ubuntu or whichever distribution you installed from the Microsoft Store. Run the commands docker —version and docker-compose —version to verify that the installation was successful. 

    3. Installing Docker on Linux 

    It's a little bit different to install Docker on Linux, and the procedure may differ even more depending on the distribution you're using. However, the installation is actually just as simple—if not simpler—than the other two platforms. A selection of technologies including Docker Compose, Docker Dashboard, Docker Engine, Kubernetes, and a few other goodies are included in the Docker Desktop bundle for Windows or Mac. 

    On Linux, though, there isn't a bundle like that. Instead, you manually install all the required tools. The following is the installation process for several distributions:  

    • If you're using Ubuntu, you can refer to the official documentation's Install Docker Engine on Ubuntu article. In the official documentation, installation instructions for each distribution are available.  
    • Docker Engine installation on Debian Fedora installation of Docker Engine CentOS Docker Engine installation 

    Instead, you could refer to the Install Docker Engine from Binaries tutorial if your distribution isn't one that is mentioned in the documentation.  

    • No matter the technique that you choose, you'll need to complete some crucial Linux post-installation activities.  
    • Following the completion of the Docker installation, you must install the Docker Compose tool. You can follow the official documentation's instructions for installing Docker Compose.  

    Open a terminal and type docker —version and docker-compose —version to verify the installation was successful after it is complete. 

    Docker Swarm  

    Docker Swarm is a container orchestration device that enables the control of containers throughout more than one host machine. It works through clustering a collection of machines together; as soon as they are in a group, you can run Docker instructions as you usually would. 

    If you want to use secrets with your Docker container and through Docker Compose secrets, you may want to ensure that you are running your Docker Engine in swarm mode. 

    Secrets Management  

    Secrets management is an essential element of container protection for any utility that deals with configuration variables, API tokens, passwords, SSH keys, non-public certificates, or other records that shouldn’t be available to anybody outside of your organization. 

    Secrets can be used to authenticate and grant access to applications and services while also proving the identity of a user. You must keep, synchronize, and rotate all secrets whenever you begin running several instances of your containerized apps. 

    In a microservice architecture, sharing a known secure key or token to authenticate communication between services is another typical use case. Both involve the persistence and pre-population of sensitive data in our containers (for instance, database credentials that might change between environments). 

    How to Enable Swarm Mode 

    Because swarm mode is not activated (docker secrets without swarm) by default, you will need to run the following command to initialize your machine: 

    docker swarm init 

    When you run this command, your local system becomes a swarm manager. 

    How to Create Your First Secret 

    openssl rand -base64 128 | docker secret create secure-key - 
    docker service create --secret="secure-key" redis:alpine 

    To use the secret, your application must read its contents from the temporary filesystem established under /run/secrets/secure-key, which is stored in memory: 

    > cat /run/secrets/secure-key  

    Swarm and Secrets  

    According to the documentation, there are a couple of extra points to consider while utilizing Docker Swarm for secrets: 

    • Secret Docker access granted to a service may be terminated at any time.  
    • A service that has just been started or that is already active can be given access to a secret, after which the decrypted secret is mounted into the container as part of an in-memory file system. 
    • Only nodes that are serving as swarm managers or carrying out service duties that have been given access to a secret are permitted access to secrets. 
    • When a container job terminates, the decrypted secrets shared with it are unmounted from the filesystem of that container and removed from the node's memory. 

    How to Use Secrets with Compose  

       image: mysql:latest 
        - db_data:/var/lib/mysql 
        MYSQL_ROOT_PASSWORD_FILE: /run/secrets/db_root_password 
        MYSQL_DATABASE: wordpress 
        MYSQL_USER: wordpress 
        MYSQL_PASSWORD_FILE: /run/secrets/db_password 
        - db_root_password 
        - db_password 
        - db 
       image: wordpress:latest 
        - "8000:80" 
        WORDPRESS_DB_HOST: db:3306 
        WORDPRESS_DB_USER: wordpress 
        WORDPRESS_DB_PASSWORD_FILE: /run/secrets/db_password 
        - db_password 
       file: db_password.txt 
       file: db_root_password.txt 

    Let's dissect the aforementioned file. What's happening is as follows: 

    • You can inject Docker secrets into a particular container by specifying them in the secrets line under each service. 
    • The variables dB password and dB root password, as well as the file that should be used to set their values, are described in the main secrets segment. 
    • When a container is deployed, Docker makes a temporary filesystem mount under /run/secrets/secret name> with its unique values. 

    In contrast to the other techniques, this ensures that secrets are only accessible to the services to which access has been explicitly allowed and that secrets reside only in memory while that service is active. 


    You should now be aware of some of the most typical errors programmers make when developing containerized applications that include confidential or sensitive data. You can maintain the security of your applications by being aware of and avoiding these errors. Also, take a look at our Docker Kubernetes certification. 

    Frequently Asked Questions (FAQs)

    1What do you mean by secrets in Docker?

    Docker secrets are offered by Docker as a part of its secrets management service. 

    2How can I get a Docker secret’s value?

    By using the docker secret inspect command. 

    3What is a secret file?

    Secrets are Kubernetes objects that are used to encrypt and store private information such as user names and passwords.

    4Can Docker images be encrypted?

    Using the —layer flag, you can encrypt only particular image layers.


    Geetika Mathur


    Geetika Mathur is a recent Graduate with specialization in Computer Science Engineering having a keen interest in exploring entirety around. She have a strong passion for reading novels, writing and building web apps. She has published one review and one research paper in International Journal. She has also been declared as a topper in NPTEL examination by IIT – Kharagpur.

    Share This Article
    Ready to Master the Skills that Drive Your Career?

    Avail your free 1:1 mentorship session.

    Your Message (Optional)

    Upcoming DevOps Batches & Dates

    NameDateFeeKnow more
    Course advisor icon
    Course Advisor
    Whatsapp/Chat icon