:original_name: cce_10_0462.html

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Container Engine
================

Introduction to Container Engines
---------------------------------

Container engines, one of the most important components of Kubernetes, manage the lifecycle of images and containers. The kubelet interacts with a container runtime through the Container Runtime Interface (CRI).

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Mapping between Node OSs and Container Engines
----------------------------------------------

.. table:: **Table 1** Node OSs and container engines in CCE clusters

   +-------------+----------------+-------------------------------------------------+-----------------------------------------------------+-------------------+
   | OS          | Kernel Version | Container Engine                                | Container Storage Rootfs                            | Container Runtime |
   +=============+================+=================================================+=====================================================+===================+
   | CentOS 7.x  | 3.x            | Docker                                          | Clusters of v1.19.16 and earlier use Device Mapper. | runC              |
   |             |                |                                                 |                                                     |                   |
   |             |                | Clusters of v1.23 and later support containerd. | Clusters of v1.19.16 and later use OverlayFS.       |                   |
   +-------------+----------------+-------------------------------------------------+-----------------------------------------------------+-------------------+
   | EulerOS 2.5 | 3.x            | Docker                                          | Device Mapper                                       | runC              |
   +-------------+----------------+-------------------------------------------------+-----------------------------------------------------+-------------------+
   | EulerOS 2.9 | 4.x            | Docker                                          | OverlayFS                                           | runC              |
   |             |                |                                                 |                                                     |                   |
   |             |                | Clusters of v1.23 and later support containerd. |                                                     |                   |
   +-------------+----------------+-------------------------------------------------+-----------------------------------------------------+-------------------+

.. table:: **Table 2** Node OSs and container engines in CCE Turbo clusters

   +-----------------------------------------+-------------+----------------+------------------+--------------------------+-------------------+
   | Node Type                               | OS          | Kernel Version | Container Engine | Container Storage Rootfs | Container Runtime |
   +=========================================+=============+================+==================+==========================+===================+
   | Elastic Cloud Server (VM)               | CentOS 7.x  | 3.x            | Docker           | OverlayFS                | runC              |
   |                                         |             |                |                  |                          |                   |
   |                                         | EulerOS 2.9 |                |                  |                          |                   |
   +-----------------------------------------+-------------+----------------+------------------+--------------------------+-------------------+
   | Elastic Cloud Server (physical machine) | EulerOS 2.9 | 4.x            | containerd       | Device Mapper            | Kata              |
   +-----------------------------------------+-------------+----------------+------------------+--------------------------+-------------------+

Differences in Tracing
----------------------

-  Docker (Kubernetes 1.23 and earlier versions):

   kubelet --> docker shim (in the kubelet process) --> docker --> containerd

-  Docker (community solution for Kubernetes v1.24 or later):

   kubelet --> cri-dockerd (kubelet uses CRI to connect to cri-dockerd) --> docker--> containerd

-  containerd:

   kubelet --> cri plugin (in the containerd process) --> containerd

Although Docker has added functions such as swarm cluster, docker build, and Docker APIs, it also introduces bugs. Compared with containerd, Docker has one more layer of calling. **Therefore, containerd is more resource-saving and secure.**

Container Engine Version Description
------------------------------------

-  Docker

   -  EulerOS/CentOS: docker-engine 18.9.0, a Docker version customized for CCE. Security vulnerabilities will be fixed in a timely manner.

-  containerd: 1.4.1