.. _containers-page:

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Containers
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Linux containers
================

What are containers?
---------------------

A Container can be seen as a **minimal virtual environment** that can be used in any Linux-compatible machine (and beyond).

Using containers is time- and resource-saving as they allow:

* Controlling for software installation and dependencies.
* Reproducibility of the analysis.

Containers allow us to use **precisely the identical versions of the tools**.

Virtual machines or containers?
----------------------------------

=====================================================  =====================================================
Virtualisation                                         Containerisation (aka lightweight virtualisation)
=====================================================  =====================================================
Abstraction of physical hardware                       Abstraction of application layer
Depends on hypervisor (software)                       Depends on host kernel (OS)
Do not confuse with hardware emulator                  Application and dependencies bundled all together
Enable virtual machines                                Every virtual machine with an OS (Operating System)
=====================================================  =====================================================

.. image:: images/vms-containers.png
  :width: 800

`Source <https://dockerlabs.collabnix.com/beginners/difference-docker-vm.html>`__


**Pros and cons**

===== ===================================================== =====================================================
ADV   Virtualisation                                        Containerisation
===== ===================================================== =====================================================
PROS. * Very similar to an entire OS.     		     * No need for complete OS installation (less space).
      * High OS diversity.       			     * Better portability.
      							     * Faster than virtual machines.
							     * Easier automation.
							     * Easier distribution of recipes.


CONS. * Need more space and resources.                       * Some cases might be different from an entire OS.
      * Slower than containers.                              * Still less OS diversity, even with current solutions.
      * Not that good automation.
===== ===================================================== =====================================================