Docker vs. Singularity: Which Fits Your Workflow Better?

This article provides a clear comparison of Docker vs. Singularity for containerized workloads. It highlights each platform's architectural differences, use cases, and performance considerations. You’ll discover which solution aligns best with your cloud-native or high-performance computing needs.

Are you using the right container for your cloud and HPC workloads?

As more teams rely on containers for everything from development to research, choosing the right tool has become harder. Docker is popular in cloud-native apps and DevOps. Conversely, Singularity works better for high-performance computing, where security and reproducibility matter most.

Each tool solves different problems, but which one fits your needs?

This article on Docker vs Singularity breaks down the key differences in design, performance, and use cases. Whether building microservices or running scientific models, you’ll get the clarity you need to make the right choice.

Keep reading.

What is the difference between Singularity and Docker?

Docker and Singularity are container runtimes, but they serve different communities and operate on distinct architectural models.

Origin and Purpose

• Docker was launched in 2013 to deploy general-purpose software. It’s the go-to for developers building microservices and cloud apps.

• Singularity was created in 2015 specifically for scientific computing and HPC clusters. It is designed to work without root access and be secure in multi-user environments.

Architecture & Security

Feature	Docker	Singularity
Requires daemon?	Yes (docker daemon)	No
Runs as root?	Yes, potentially risky in HPC	No, respects same user execution
Suitable for HPC?	No, most clusters prohibit it	Yes, built for HPC workloads
Security model	Requires tight control over user groups	User privileges are preserved

Docker containers run through a background service, the Docker daemon, which requires root privileges. This raises security concerns in multi-user environments like HPC clusters. In contrast, Singularity containers run under the user inside the system. There’s no background daemon, reducing risks significantly.

Can Singularity run Docker containers?

Yes. One of Singularity’s strengths is that it can pull and run Docker containers without installing Docker.

1singularity pull docker://ubuntu

The following command downloads the Docker image and converts it into a Singularity image file (.sif). The image is stored locally, can be run securely, and requires no daemon.

This compatibility is a huge advantage: it lets researchers leverage the extensive ecosystem of Docker container images hosted on the Docker Hub while operating safely in HPC environments.

Why Singularity is Favored in HPC?

Singularity aligns well with the strict requirements of high-performance computing:

• Runs without root privileges

• Integrates with schedulers like SLURM, PBS, and Torque

• Supports MPI, GPUs, and InfiniBand

• Preserves user identity, making it ideal for shared systems

Furthermore, Singularity emphasizes reproducibility. Every container is a single file, built via a definition file that includes the OS, environment variables, and the software stack.

Example build process:

1sudo singularity build my_container.sif my_def.def

The sif (singularity image format) makes sharing and auditing much easier, especially in collaborative scientific computing projects.

Docker in Development and Cloud Workflows

On the other hand, Docker remains unmatched in the cloud-native and DevOps ecosystems:

• Rich CLI and GUI tooling

• CI/CD integration

• Built-in orchestration via Swarm and compatibility with Kubernetes

• Access to a vast public registry through Docker Hub

• Ideal for production environments where container orchestration matters

The following command builds a Docker image:

1docker build -t myapp .

And to run it:

1docker run myapp

These commands are streamlined for developer workflows. Docker containers are highly portable but may require special configuration to run efficiently in HPC environments.

Singularity’s Strength: Portability, Security, and Reproducibility

The singularity image format (.sif) encapsulates everything needed to run the container:

• Operating system base

• Application binaries

• Configuration files

• Dependencies

This single, immutable file eliminates the need to manage layered container images or worry about mismatched environments.

Another key advantage: Singularity shell. This gives direct, interactive bash shell access inside the container:

1singularity shell my_container.sif

Unlike Docker, where the user might gain root-like access inside the container, Singularity shell maintains the same user identity, increasing security and predictability across systems.

Compatibility & Integration

Feature	Docker	Singularity
Image registry	Docker registry, Docker Hub	Singularity Hub, Docker registry compatible
Image formats	.tar, .img, layered OCI	.sif (singularity image format)
Run containers?	docker run	singularity run
Shell access?	docker exec -it	singularity shell

Both support container images, but Singularity packages them into a single file, simplifying transport and version control. Thanks to its support for the Open Container Initiative standards, you can also build images from Docker sources.

When to Use Which?

Choose Docker if:

• You’re working in cloud or production environments

• You rely on microservices or modern web frameworks

• You use Kubernetes or need dynamic scaling

• You want access to the Docker Hub and its massive image library

Choose Singularity if:

• You work in HPC clusters or multi-user environments

• Your job involves scientific computing

• You need precise reproducibility and user-level security

• You require MPI, GPU access, or node-level hardware control

Summary Table: Key Differences

Aspect	Docker	Singularity
Daemon needed?	Yes	No
Root required?	Yes	No
Ideal for	Cloud, DevOps, Web apps	HPC, Research, Academic
Default image type	Docker image	Singularity image format
Build tool	Dockerfile	Definition file
Registry support	Docker Hub, private registries	Singularity Hub, Docker registry
Shell access	docker exec	singularity shell
User privileges	Escalated (needs control)	Preserved (runs as same user)

Choose Containers that Fit Your Workload Strategy

Selecting Docker or Singularity depends on your environment, performance goals, and how your teams collaborate across systems.

Docker works well for DevOps and cloud deployments. Singularity supports high-performance computing with strong security and reproducibility.

Your container choice shapes long-term flexibility and project stability as demands grow.

Start by reviewing your current needs and future goals. Then, pick the container platform—or combination—that supports your direction. Make the right move in the Docker vs. Singularity decision before technical debt slows your progress.