Singularity VS Docker

Docker is a software platform that helps users by simplifying the process of running, distributing, building, and managing applications. Though Docker is one of the well-known containerization systems in the market it is not good for data processing. Access to the file system which includes using correct UIDs is also not possible in docker since it was not designed for this use case. Many containers are there in the market that are more efficient than Docker, Singularity is one such! It was explicitly designed to process the data efficiently. Singularity is also similar to Docker but it begins from a different place. Unlike Docker, it does not support isolation but favours integration. This article will help you to understand the difference between Docker & Singularity!

What is Docker?

Docker is a platform that is open source that allows its users to build, update, run, and deploy applications easily. It also helps in managing the containers efficiently. The concept of containers has now become very popular as all the organisations have started shifting development to cloud native. Docker makes the process of containerization faster and also safer.  It works by providing a standard mechanism to run the code.  Docker consist of the following elements

  • Daemon
  • High-level API ( Application Programming Interface)
  • CLI (Command Line Interface)

To sum up, a Docker container is a collection of all the dependencies and application libraries that are prebuilt and can be executed anytime. The only reason for all the companies to migrate to containers is it’s extremely simple and easy to maintain. 

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What is Singularity?

Singularity is a type of container platform similar to Docker. It allows the users to create and run the containers in a way that all the software pieces of the package can be reproduced. The user can build a container using the laptop and then run it on HPC clusters. Here, a container is a single file and there is no need to worry about installing the software needed on each operating system. The primary reason for creating singularity was to run complex applications. It is also an open-source project that has a good community of users and developers across the globe. Singularly is on a spree of expansion as the user base is increasing. 

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Difference Between Both (Singularity Vs Docker)

Primary Focus:

The primary focus of Docker is to automate the process of deploying applications inside the software containers. It also helps in automating the process of containerization that is supported on Linux. A docker is lightweight compared to other containers in the market. It also boosts in seconds.

While singularity's primary focus is to run all the complex applications on high-performance computing (HPC) clusters in a very portable, simple, and reproducible method. Reproducible means the ability of the containers to move the applications from one system to another. 

Portability:

Portability is one of the main features of using containers and docker. In docker, the user can spin up an application on a public cloud or on-site environment in a couple of minutes. This is possible because storage technology is implemented as a layer known as a “copy on write” to store the data in a file system which is used by docker itself. 

The primary reason for developing singularity was for portability and reproducibility features. It bases the design philosophy on the files. In singularity, everything is a file. The user can not only manipulate but also interact easily with both the persistent filesystem overlay ( this can be either file or a directory) and the immutable singularity image. 

Performance:

Dockers containers are not very fast. Though docker is comparatively faster than the virtual machine, it still cannot beat the speed of the bare metal machine. Many performance measures overheads that are associated with containers due to communication problems between containers and the host systems, networking, and many more. 

Singularity containers help to improve ease of use and reproducibility in the analysis of computation image workflows Thus the performance of singularity is better than docker.

Security:

One of the major challenges of running the applications in a virtual environment is security. Thus securing a docker container is important. The user will have to secure it everywhere from the host to the network. When compared to traditional machines, docker has a safe environment. It splits up the application into small components. These components are then isolated from one other thereby reducing the chance of attacks. It is difficult to breach security and attacks as hackers are prevented so that the computer systems are not exploited.

In singularity the root file system of the container can be encrypted therefore everything which is inside the container becomes inaccessible without having a passphrase or the correct key. The content remains private in the container even if the SIF file is shared with the public.

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Container build-up: 

Following steps should be followed for building the container in Docker and Singularity

Docker 

  • First, figure out the Docker specification file.
  • Build an interactive container, then use docker commit.
  • Then, pull all the existing images from the repository which can be either docker store, docker hub, or a private repository.       

Singularity

  • The first step is to create a def file in singularity. All the packaged dependencies are analyzed and also incorporated into the images automatically.
  • By leveraging the sudo singularity shell the user needs to expand the existing images.
  • Now, import or convert a docker image by using a singularity import into an image.
  • Then, share the prebuilt singularity images.

Deployment: 

The following steps are followed for the deployment of the two:

Docker: 

  • Docker can be deployed using a single package installation
  • Then, run the daemon service and containers in docker with root privileges to prevent all the possible vulnerabilities.
  • The user then can utilise it in batches.

Singularity

The first step is to build a Singularity container on your local system where you have root or sudo access i.e personal computer where singularity is installed. The user can also build the container from scratch using a recipe file, or you can also convert containers from one to another. Then, your containers need to be spawned with an interactive shell session. Then, execute a command inside the container. Transfer your containers to the High-Performance Computing system where you want to run them. Finally, run the singularity containers on the system.

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Pros and Cons of Singularity and Docker

Docker

Pros :

  • Docker ensures that the applications that run on the containers are segregated and isolated to prevent them from hacker’s attacks
  • It is simple and gives its users the flexibility of faster configuration
  • It facilitates the users with continuous integration. It works well with various tools such as Wercker, Jenkins, and Travis.
  • It helps in rapid deployment i.e it can decrease a deployment to seconds

Cons:

  • Many features such as self-inspecting, copying the files, and self-registration are missing in Docker.
  • If compared to the traditional virtual machines Docker has fewer overheads but not zero.
  • If an application is designed to run Docker on windows, it won't run on Linux. It becomes less attractive in places that are composed of Linux and Windows servers.
Singularity

Pros :

  • Branching and copying the entire container is easy and simple in a single file imager.
  • Large-scale performance is efficient.
  • It allows integration, unlike Docker.
  • Singularity was designed to solve complex problems using HPC systems

Cons:

  • To run a singularity container locally, a user will have to install a lot of dependencies such as virtual box, vagrant, Bash, and Git.
  • Since Singularity has less user base it might be challenging for the new learners to build applications using it.
Conclusion

Hope you have now understood the basic concept of both Docker & singularity. Though both are designed for the containerization process each has its purpose. Docker is one of the preferred choices of all the developers across the globe. It has both Windows and Mac integration and various other tools to support it. But, if you want to process a batch then singularity is a better tool as compared to Docker. If you have any queries you can comment in the section below. 

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Srivalli
Srivalli
Research Analyst
As a senior technical content writer for HRK tainings, srivalli patchava has a greater understanding of today's data-driven environment, which includes key aspects of data management and IT organizations. She manages the task of creating great content in the areas of software testing, DevOps, Robotic process automation. Connects with her on Linkedin and Twitter.

Yes, Singularity uses Docker for its images. This is because most developers around the world prefer using Docker.

No, Singularity is not a popular tool. The ecosystem of Docker is much bigger than Singularity. It is supported by both Windows and Mac integration. But, in the case of singularity, it only has beta mac support and not windows.

Singularity containers are stored in a default cache directory.

No, Docker is not a good choice to containerize HPC workloads.