Kuber­netes vs. Docker - What’s the dif­fer­ence?

Docker is a platform for creating, packaging, and running ap­plic­a­tions in con­tain­ers, while Kuber­netes is an or­ches­tra­tion system that manages and scales those con­tain­ers. In other words, Docker handles the con­tain­er­iz­a­tion of ap­plic­a­tions, and Kuber­netes takes care of auto­mat­ic­ally deploying, or­gan­iz­ing, and scaling them.

What are the dif­fer­ences? Kuber­netes vs. Docker

Docker has achieved a small re­volu­tion with the de­vel­op­ment of container tech­no­logy. For work in software de­vel­op­ment, vir­tu­al­iz­a­tion with self-contained packages (the con­tain­ers) offers com­pletely new pos­sib­il­it­ies. De­velopers can easily bundle ap­plic­a­tions and their de­pend­en­cies in con­tain­ers, ensuring that vir­tu­al­iz­a­tion can occur at the process level. Although there are a number of Docker al­tern­at­ives, the open-source solution Docker remains the most popular platform for creating con­tain­ers.

Kuber­netes, on the other hand, is an ap­plic­a­tion for or­ches­tra­tion (that is, man­age­ment) of con­tain­ers; the program itself does not create the con­tain­ers. The or­ches­tra­tion software accesses the existing container tools and in­teg­rates them into its own workflow. Thus, con­tain­ers created with Docker or another tool are easily in­teg­rated into Kuber­netes. Then, you use or­ches­tra­tion to manage, scale, and move the con­tain­ers. Kuber­netes ensures everything runs as desired and also provides re­place­ments if a node fails.

Use cases for Docker and Kuber­netes

In the com­par­is­on of Docker vs. Kuber­netes, it is no­tice­able that the two tools differ in their use cases but work hand in hand. To un­der­stand the different functions of Docker and Kuber­netes, let’s look at an example.

Most ap­plic­a­tions today are organized with mi­croservice ar­chi­tec­tures because this ar­chi­tec­tur­al style allows for better scalab­il­ity, flex­ib­il­ity, and main­tain­ab­il­ity by breaking down complex systems into smaller, in­de­pend­ent services.

Step 1: Program mi­croservices and create con­tain­ers

In the first step, the ap­plic­a­tion must be pro­grammed; the team develops the in­di­vidu­al mi­croservices that make up the app. Each mi­croservice is written as a stan­dalone unit and has a defined API for com­mu­nic­a­tion with other services. Once the de­vel­op­ment of a mi­croservice is completed, it is con­tain­er­ized with Docker. Docker allows mi­croservices to be packaged into small, isolated con­tain­ers that contain all necessary de­pend­en­cies and con­fig­ur­a­tions. These con­tain­ers can then be run in any en­vir­on­ment without com­plic­a­tions arising from different system con­fig­ur­a­tions.

Step 2: Configure or­ches­tra­tion with Kuber­netes

After the mi­croservices have been suc­cess­fully con­tain­er­ized, Kuber­netes comes into play. In the next step, the team creates Kuber­netes con­fig­ur­a­tion files that specify how the con­tain­ers (in Kuber­netes lingo, these are also called Pods) should be deployed across different servers. The files include details such as how many instances of a par­tic­u­lar pod should be run, what network settings are required, and how com­mu­nic­a­tion between the mi­croservices works.

Kuber­netes takes care of the automatic man­age­ment of these con­tain­ers. If a mi­croservice fails or a container crashes, Kuber­netes ensures that the container is auto­mat­ic­ally restarted, allowing the ap­plic­a­tion to continue func­tion­ing without system outages. Ad­di­tion­ally, Kuber­netes can perform the function of a load balancer and dis­trib­ute con­tain­ers across multiple servers to ensure better util­iz­a­tion and scalab­il­ity. If traffic for the ap­plic­a­tion increases, Kuber­netes can auto­mat­ic­ally start new pods.

Step 3: Updates

With Kuber­netes, not only is the de­ploy­ment of con­tain­ers sim­pli­fied, but also the man­age­ment of updates. If the de­velopers want to bring new code into pro­duc­tion, Kuber­netes can gradually replace the con­tain­ers with the new version without causing downtime. This ensures the ap­plic­a­tion remains con­stantly available while new features or bug fixes are im­ple­men­ted.

Direct com­par­is­on of Kuber­netes vs. Docker

Docker Swarm, the Kuber­netes al­tern­at­ive

Even though Kuber­netes and Docker work won­der­fully together, there is still a com­pet­it­or for the or­ches­tra­tion tool: Docker Swarm combined with Docker Compose. While Docker can handle both solutions and even switch between the two, Docker Swarm and Kuber­netes cannot be combined. Therefore, users often face the question of whether to rely on the very popular Kuber­netes or to use Swarm, which is part of Docker.

The structure of the two tools is es­sen­tially very similar – only the names of the in­di­vidu­al aspects change. The purpose is also identical, which is to manage con­tain­ers ef­fi­ciently and ensure the most eco­nom­ic­al use of resources through in­tel­li­gent scaling.

Swarm reveals ad­vant­ages in in­stall­a­tion: Since the tool is an integral part of Docker, the trans­ition is very easy. While you have to set up or­ches­tra­tion with Kuber­netes first—which ad­mit­tedly isn’t very complex—everything is already there with Swarm. Since you are most likely already working with Docker in practice, you don’t need to fa­mil­i­ar­ize yourself with the specifics of a new program.

Kuber­netes shines with its own GUI: The ac­com­pa­ny­ing dashboard provides not only an excellent overview of all aspects of the project but also enables the com­ple­tion of numerous tasks. Docker Swarm, on the other hand, offers such con­veni­ence only through ad­di­tion­al programs. Kuber­netes also stands out in terms of func­tion­al­ity: unlike Swarm, which needs extra resources for mon­it­or­ing and logging, Kuber­netes includes these cap­ab­il­it­ies by default as part of its core features.

The main benefit of both programs lies in scaling and ensuring avail­ab­il­ity. It is said that Docker Swarm is generally better in terms of scalab­il­ity. This is due to the com­plex­ity of Kuber­netes, which leads to a certain slug­gish­ness. However, the complex system ensures that automatic scaling with Kuber­netes is better. Ad­di­tion­ally, a sig­ni­fic­ant advantage of Kuber­netes is that it con­tinu­ously monitors the state of the con­tain­ers and directly com­pensates for any failures.

Swarm has an edge in load balancing as it provides even dis­tri­bu­tion right out of the box. With Kuber­netes, achieving load balancing requires an extra step—de­ploy­ments need to be converted into services before traffic can be evenly dis­trib­uted.