====== Container Technology ======

Building more complex processing and analysis pipelines within a container can offer several advantages:

   * The container fully encapsulates the job and all software dependencies
   * Software dependencies do not need to be installed on the HPC facility
   * Your workflow can easily be replicated or moved between other systems
   * You can run //pre-built// job containers which application developers publish
   * You can build //your own// containers to move between systems, or share with your group

The **Comet** HPC facility supports the following container tools:

   * [[#docker|Docker]]
   * [[#apptainer|Apptainer]]
   * [[#apptainer|Singularity]] - Now //deprecated// and replaced by [[#apptainer|Apptainer]]
   * [[#podman|Podman]] - RedHat Linux specific container toolset, largely compatible with Docker

Unlike Rocket, Comet is design to be __fully native container aware__ - all tools are configured to allow the running of container jobs under Slurm from the above technologies, enabling the community to take advantage of the increased number of ready-built container images available to them from various software developers.

Please note that we __do not__ have support for Kubernetes at this time.

<WRAP todo round>
**This section is incomplete**

This documentation section on //Container Technology// is still being written and will not be complete until the **Comet** HPC facility is fully commissioned.
</WRAP>
===== Docker =====

   * [[:advanced:docker|Docker help guide]]

----
===== Apptainer =====

If you have used Singularity previously, then [[https://apptainer.org/|Apptainer]] is a 100%, like-for-like replacement. You can create container images which exist in a single file and are easy to transport between different systems and provide a consistent environment for your software, reducing the need for the installation of additional libraries and other dependencies.

You can use Apptainer to **build** and **run** container images on the Comet login nodes, as well as **run** container images on any of the available compute nodes. 

Please read our full guide on using Apptainer on Comet, which is linked below, or can be accessed from the [[:advanced:software|Advanced Software Topics]] section of the wiki:

   * [[:advanced:apptainer|Apptainer help guide]]

----
===== Singularity =====

Singularity is now deprecated and the community have largely moved to Apptainer instead - an alternative version of Singularity now exists named SingularityCE; we __do not__ support SingularityCE.

== Singularity CE ==

SingularityCE is the 'free' version maintained by a commercial entity (Sylabs). This software __is not installed on Comet__ and we __do not__ support it.

== Apptainer ==

Apptainer is a like-for-like, drop-in replacement for Singularity, is open-source and supported by the Linux foundation. We have this tool installed on Comet and we //provide support// for it.

If you have previously used Singularity, then you can start using Apptainer by simply changing any call to ''singularity'' to ''apptainer'' instead. Historically we //did// have Singularity on our previous **Rocket** HPC facility, but it was not advertised and was very much a "use at your own risk" capability.

You are encouraged to read our [[:advanced:apptainer|Apptainer help guide]] to be aware of any specification configuration or limitations with the use of the technology on Comet.

----
===== Podman =====

[[https://podman.io/|Podman]] is a container technology tool somewhat similar to Docker, but has a slightly different implementation making it easier to integrate into existing systems; it is often preferred to Docker due to being easier to run by a non-admin user. From a user perspective it has much of the same rich functionality as Docker and is more suited to expert users than something like Apptainer.

Using Podman to **build** or **run** containers on the Comet login nodes as well as **run** containers on the Comet compute nodes is fully supported.

Please read our Podman help guide for a walk-through of how to use Podman on Comet.

   * [[:advanced:podman|Podman help guide]]

----

[[advanced:index|Back to Advanced Topics]]