Container resource usage stats in Docker - Commands & Configuration

Introduction

Sometimes containers use too much memory or CPU and slow down your system. Checking resource usage helps you find which container is causing the problem and fix it quickly.

When your server feels slow and you want to see if a container is using too much CPU.

When you want to monitor memory use of a container running a database to avoid crashes.

When you need to check network traffic of a container to troubleshoot slow responses.

When you want to track resource use over time to plan for scaling your app.

When you want to confirm that resource limits you set on containers are working.

Commands

This command lists all running containers so you can see their names and IDs before checking their stats.

Terminal

docker ps

Expected Output

CONTAINER ID   IMAGE          COMMAND                  CREATED       STATUS       PORTS                    NAMES

b1c2d3e4f5g6   nginx:1.23     "/docker-entrypoint.…"   2 hours ago   Up 2 hours   0.0.0.0:8080->80/tcp     my-nginx

7h8i9j0k1l2m   redis:7.0      "docker-entrypoint.s…"   3 hours ago   Up 3 hours   6379/tcp                 my-redis

This command shows the current CPU, memory, and network usage of the container named 'my-nginx'. The --no-stream flag makes it show the stats once and then stop.

Terminal

docker stats my-nginx --no-stream

Expected Output

CONTAINER ID   NAME      CPU %     MEM USAGE / LIMIT     MEM %     NET I/O           BLOCK I/O         PIDS

b1c2d3e4f5g6   my-nginx  0.15%     12.3MiB / 1GiB        1.20%     1.2MB / 1.1MB     0B / 0B           5

→

--no-stream - Show stats only once instead of continuously updating

This command shows live resource usage stats for all running containers, updating every second until you stop it with Ctrl+C.

Terminal

docker stats

Expected Output

CONTAINER ID   NAME      CPU %     MEM USAGE / LIMIT     MEM %     NET I/O           BLOCK I/O         PIDS

b1c2d3e4f5g6   my-nginx  0.20%     12.5MiB / 1GiB        1.22%     1.3MB / 1.2MB     0B / 0B           5

7h8i9j0k1l2m   my-redis  0.05%     8.7MiB / 512MiB       1.70%     0.5MB / 0.4MB     0B / 0B           3

Key Concept

If you remember nothing else from this pattern, remember: docker stats shows real-time resource use of containers to help you monitor and troubleshoot performance.

Common Mistakes

Running 'docker stats' without specifying --no-stream when you only want a single snapshot.

The command keeps running and updating, which can be confusing if you expect just one output.

Add the --no-stream flag to get a one-time snapshot of container stats.

Trying to check stats of a container that is not running.

Docker stats only works for running containers and will show an error or no output.

Use 'docker ps' first to confirm the container is running before checking stats.

Summary

Use 'docker ps' to list running containers and find their names or IDs.

Use 'docker stats container-name --no-stream' to get a one-time snapshot of resource usage.

Use 'docker stats' to watch live resource usage of all running containers until you stop it.