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!
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
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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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.
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 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.
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.
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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Following steps should be followed for building the container in Docker and Singularity
The following steps are followed for the deployment of the two:
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.
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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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.