Tips and best practices for Docker

• Numerous packaging & delivering applications are available in the global market, and out of all,
Docker has created its prominent reputation amongst countless organizations around the globe,
especially for cloud-based applications.
• Docker is a widely used platform to develop & run apps quickly by allowing users to keep them
separate from the infrastructure. Docker’s testing & deploying methodologies help to mitigate the
delays between writing codes & running them.
• Docker provides phenomenal benefits such as the cluster of containers, scalability, & rapid
deployment with any dependencies. In this blog, we will walk you through the best practices of
Docker in detail that will help you maximize the benefits of Docker by implementing them.
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Tips and best practices for Docker

Version Images
• Docker users employ the latest tags for images, which are also the default tag. Using these tags will
eliminate the possibility of identifying the running version code based on the image tag.
• It makes it straightforward to overwrite it. However, it leads to severe complications while doing
rollbacks. Please avoid using the latest tag, especially for primary images, as it could lead to
deploying a new code version.
• The best practice is using descriptors such as timestamps, semantic versions, or Docker Image IDs as
tags. You can easily tie the tag to the code with the relevant tagging.
Docker Best Practices for Image Building

Imaging Linting
• Inspection of the source for any programmatic error that can cause issues is called Linting, which
helps to ensure that the Dockerfiles comply with the correct practices. You can follow this process in
images to determine any root-level vulnerabilities.
Signing & Validating Images
• There are scenarios when tampering with the images can occur due to human errors while running
the production code. Using Docker Content Trust, you can sign & validate the images to determine
whether they have been tampered with. You need to set up the DOCKER_CONTENT_TRUST=1
environment variable.

Using .dockerignore File
• .dockerignore file helps to define the required build context. The user needs to specify the files &
folders before image building that should be excluded from the initial build context, which is sent to
the Docker Daemon with the help of the .dockerignore file. The entire project’s root is sent to the
Docker Daemon before evaluating the COPY or ADD command.
• If the Docker Daemon and Docker CLI are on different machines, then the .dockerignore file should
be added to the local development file, build logs, or temporary files. It will boost the build process,
minimize the risk of secret leaks, and reduce Docker image size.

Avoid secrets storage in Images
• Confidential data and secrets, such as passwords, TLS certificates, SSH keys, and other highly
sensitive information, must be avoided storing in images without encryption as it can lead to easy
extraction and exploitation of confidential information. These situations can occur when images are
pushed into a public registry.
• The best practice is injecting confidential information through environment variables, orchestration
tools, and build-time arguments. You can also store sensitive information in the .dockerignore file.
Also, ensure being specific about the files that must be copied over the image.

• Environment Variables are primarily employed to keep the application secured & flexible. It can also
be used to pass on highly sensitive information and secrets. However, this information will still be
visible in linked containers, docker inspect, logs, and child processes. We recommend encrypting the
secrets if they need to be shared in a shared volume.
Multi-Stage Builds
• You can divide Dockerfiles into numerous stages via Multi-Stage Builds. With this break-up, you can
easily discard the tools & dependencies of application building in the final stage. In addition, Multi-
Stage Builds lead to lean, modular, low-size, and secure images, thereby helping you save time &
cost.
Dockerfiles Best Practices

Reducing Layers Number
• The image size increases with every layer due to caching. The best practice is to keep the image size
minimal. You can reduce the number of layers by combining related commands wherever feasible.
• Apart from this, you can eliminate unwanted files in the RUN setup. Also, you can minimize the run
apt-get update to achieve this task. However, reduce the number of layers whenever possible and
not forcefully, as it can lead to irrelevant issues.

Small Docker Base Images
• The best practice for building, pushing, and pulling images is to ensure their size is as small as
possible, which will fasten up the process and keep it safer. Also, ensure that only the essential
dependencies & libraries are included to run the application.

Using a single container for one process
• Running only one process per container is always advisable, even though an app stack can run
multiple functions in a single container. It is one of the best practices for Dockerfiles as it makes the
following services straightforward:
 Scalability
You can manage traffic by horizontally scaling the services with a single container.
 Portability
With a single container, there are fewer processes to work on, making security patches plain sailing.
 Reusability
You can employ the same database container when another service requires a containerized database.

Dockerfile Command Order
• Dockerfile commands play a pivotal role in its efficiency. Docker caches every layer in a specific
Dockerfile to improve the builds. During any change in a step, the entire cache will become null for
further steps, which is a highly inefficient practice in a Docker container.
• Instead of randomly putting files, the correct practice is to place frequently updated files at the end
of the Dockerfile. You can also put layers with a higher possibility of lower changes in the Dockerfile
and turn off cache in a Docker build wherever necessary by adding a “–no-cache=True flag.”

Using COPY instead of ADD
• Many users perceive that both COPY & ADD commands have the same purpose and nature as they
are used to copy files from one location to a Docker image. However, there are differences between
both. COPY helps to copy local files from the Docker host to the image.
• ADD also does the same, but it can also download external files & unpacking the contents of any
compressed file in a desired location. The primary preferred command should be COPY over ADD.
However, you can use ADD if you want the additional functionality of the ADD command.

CI/CD for Testing & Deployment
• When a pull request is created, Docker experts recommend employing Docker Hub or any other
CI/CD pipeline to develop & tag a Docker image. Also, the images must be signed by development,
testing, and security teams before pushing them to production to ensure they are constantly tested
for top-notch quality.
Best Practices of Docker Development
Updating Docker
• Always update Docker to the latest version before starting to work on a Docker project, as you will
have the latest features and updates. You can utilize security features and others to protect your
project from attacks and threats.

Different Environments
• One of the best practices of Docker Development is to create different environments for
development & testing. It helps developers to keep Dockerfiles isolated & run them without affecting
the final build post-testing.
APIs & Network Configuration
• One of the biggest security threats for Docker is inappropriately configured API, which hackers can
target. Ensure to configure API securely with practices like certificate-based authentication to keep
containers secured from being exposed publicly.
Best Practices for Docker Security

Limit Container Capabilities
• Docker comes with a default configuration where users will see the capabilities that wouldn’t be
required to perform certain services. These unnecessary capabilities and benefits can be a doorway
to hackers.
• The best practice to avoid these security breaches is to limit container capabilities by employing only
those which are required by Docker containers to run apps.

Restrict System Resource Usage
• Each Docker container can use different infrastructure resources, such as CPU, network bandwidth,
and memory.
• Limiting the system resource usage for each container ensures that no container employs excessive
infrastructure resources than required. It will promote efficient use of resources, and no services will
be disrupted.
Using Trusted Images
• Using images from any source will adversely impact Docker’s security. Hence, ensure to use Docker
images only from trusted sources and configure them correctly. Also, make sure to get them signed
by the Docker Content Trust.

Limit Access to Container Files
• Transitory container files are accessed more frequently, and they need constant bug fixes & upgrades
to secure them from getting exposed.
• You can solve this issue by maintaining container logs outside containers. It will limit the access to
container files and keep them secured from getting accessed frequently.

Cloud Deployment
• While deploying a Docker container to a cloud, we recommend deploying the Kubernetes cluster. We
recommend creating a standard virtual machine by the admins to deploy a single Docker container.
The next step is securing the socket shell and installing Docker. After installation, admins can deploy
applications on the cloud.
Best Practices of Docker Container
Single Manager Node
• One of the most common Docker container practices is backing up a single manager node frequently,
helping admins in restoration. Docker Swarm & Universal Control Plane are part of every node.
Hence, backing up a single manager node gets the job done for the admins.

Load Balancer
• Load Balancer helps admins get firm control over Docker containers, and they can foster containers
to become highly scalable and available.
• A Load Balancer supports numerous balancing methods & specific applications, rate limiting, and
static & dynamic caching. If you want to install a Load Balancer on Docker, contact us, and our
proficient & highly professional Docker experts will assist you with it.

Dedicated Logging Container
• We recommend having a dedicated container for logging to eliminate dependencies on host
machines, which will be accountable for log file management within the Docker environment.
• A Dedicated Logging Container will cumulate logs from other containers. It will automatically monitor
& analyze them. Also, it will forward the log files to a desired location. You can deploy more
containers whenever needed with this Docker Logging practice.
Best Practices for Docker Logging

Application Logging
• This practice involves directly logging from the application, and applications within the container
manage to log via the framework. The developers will have firm control over the logging.
Applications remain independent from containers with this practice.
Sidecar Method
• Sidecar Method is one of the best practices for managing microservices architecture, as it runs the
sidecars simultaneously with the parent application, sharing the same network & volume. Shared
resources allow expanding the app functionalities & eliminate the installation need for extra
configurations.

Drivers Logging
• Logging Drivers help read data by the stdout or stderr streams of the Docker container, as they are
specifically configured to achieve this task. After this, the host machine stores log files, including
preliminary data.
• Logging drivers help to centralize log files to a single desired location and are primarily used because
being native to Docker.

Running Compose on a Single Server
• You can employ compose for deploying an app to a remote Docker after setting up DOCKER_HOST,
DOCKER_TLS_VERIFY, and DOCKER_CERT_PATH Environment Variables.
• After these variables are set up, the Docker compose commands will perform as desired without
requiring additional configuration.
Best Practices for Docker Compose

Adjusting Compose File for Production
• Making specific changes such as enhancing additional services, different setups for Environment
Variables, binding multiple ports on the host machine, and eliminating volume bindings are critical
for production.
• The best practice for achieving this task is defining a new compose file for specifying the desired
configuration and only adding the required changes you want from the original compose file.
• For a new configuration, you can apply a new compose file over docker-compose.yml and direct
compose to use the 2nd configuration file with the -f option.

Conclusion
• After reading the blog, you will have a firm comprehension of the Best Practices of Docker Image Building,
Dockerfiles, Docker Development, Docker Security, Docker Container, Docker Logging, and Docker Compose.
• By implementing these practices or even half of the mentioned practices in the blog, you will experience excellent
results and enjoy significant benefits. However, if you have any questions or need more tips, feel free to contact us.
• At Calidad Infotech, we utilize Docker tools as part of our DevOps services, and our Docker experts have assisted
numerous organizations in availing significant advantages of Docker in the short and long run.
• For a quotation of our Docker Tools, DevOps services, or application testing services, contact us at +91-
9909922871 or email at hello@calidadinfotech.com.

hello@calidadinfotech.com
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