All Flashcards
What is the main problem that containers promise to solve?
Using virtual machines results in a non-efficient use of resources, need of multiple guest OS.
And run applications in their own isolated environments.
What does each line of a docker image mean?
Each line creates a new filesystem layer on top of the previous ones
What are Dockerfiles used for?
Used to build docker images
What is the difference between a docker container and a docker image?
They are the same but Docker containers have an additional Read/Write layer
What is the benefit of having multiple containers with a very similar base structure?
Some containers will be able to reuse layers that other containers are using (efficient)
What is a container registry?
Registry or hub of container images - Docker hub
Can a single image generate multiple containers?
Yes, it can generate multiple containers on many different Docker hosts.
What do you use docker files for?
To build Docker container
Are containers portable?
Yes
Mention 3 characteristics/benefits of using containers
Portable.
Lightweight - layers can be reused by multiple containers.
They always run as intended
What do you need to do to allow outside access to the container?
Expose ports
Mention a benefit related to scalability and isolation:
Containers can be used to isolate different tiers of an application or to scale determined services (parts of the application)
What does ECS generally do?
It accepts containers and instructions.
It orchestrates where and how to run those containers.
Where do containers run (in ECS)?
In clusters
In which modes can you use ECS?
EC2 mode and fargate mode
Describe the ECS EC2 mode
where EC2 is the container host running the ECS software
Describe the Fargate mode
AWS manages the container host part and allows you to architect and define your environment using containers
Which registries can be used by ECS?
ECR (elastic container registry - integrated with AWS) and DockerHub.
What is a container definition in ECS?
A container definition gives ECS just enough info about the single container:
- Where the container is
- Pointer to which image to use and ports to be exposed
What does a Task definition do?
Stores the resources used by the task - represents a self contained application
What is defined in a Task definition?
- One container or many
- Resources used by the task - CPU/memory
- Task role - which allows the task to access other AWS resources
Are tasks HA by itself?
No. That is covered by ECS services
What do you need to configure an ECS service?
A service definition
What can you set up in a service definition?
- It can add capacity and resilience
- Can provides a level of scality and high availability