Why resource limits matter in Docker - See It in Action

Why resource limits matter

📖 Scenario: You are managing a small web application running inside Docker containers. Sometimes, the app uses too much memory or CPU, which slows down your computer and other apps. To keep everything running smoothly, you want to set limits on how much memory and CPU each container can use.

🎯 Goal: Learn how to set resource limits on Docker containers to prevent them from using too much memory or CPU. This helps keep your system stable and responsive.

📋 What You'll Learn

Create a Docker container running the official nginx image

Add memory and CPU limits to the container configuration

Run the container with these resource limits

Verify the container is running with the limits set

💡 Why This Matters

🌍 Real World

In real life, resource limits prevent one container from slowing down your whole system or crashing other apps.

💼 Career

Knowing how to set resource limits is important for DevOps roles to ensure applications run reliably in shared environments.

1

Create a Docker container running nginx

Write the Docker command to run a container named mynginx using the nginx image in detached mode.

Docker

# Write the docker run command to start nginx container named mynginx in detached mode
# Your code here

Need a hint?

Use docker run with -d for detached mode and --name mynginx to name the container.

2

Add memory and CPU limits variables

Create two variables: MEMORY_LIMIT set to 100m and CPU_LIMIT set to 0.5 to hold the memory and CPU limits for the container.

Docker

docker run -d --name mynginx nginx
# Define MEMORY_LIMIT and CPU_LIMIT variables below
# Your code here

Need a hint?

Use simple shell variable assignment like MEMORY_LIMIT=100m.

3

Run the container with resource limits

Write a Docker command to run the container named mynginx using the nginx image in detached mode, applying the memory limit from $MEMORY_LIMIT and CPU limit from $CPU_LIMIT.

Docker

MEMORY_LIMIT=100m
CPU_LIMIT=0.5
docker run -d --name mynginx nginx
# Run the container with --memory and --cpus options using the variables
# Your code here

Need a hint?

Use --memory $MEMORY_LIMIT and --cpus $CPU_LIMIT options in the docker run command.

4

Check the container is running with limits

Write the Docker command to show the running containers and verify that mynginx is running.

Docker

MEMORY_LIMIT=100m
CPU_LIMIT=0.5
docker run -d --name mynginx --memory $MEMORY_LIMIT --cpus $CPU_LIMIT nginx
# Write the command to list running containers
# Your code here

Need a hint?

Use docker ps to list running containers.