Here’s a complete tutorial on docker ps, covering how it works, common options, examples, and a list of use cases.

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What is docker ps?

docker ps is a Docker command used to list containers. By default, it shows only the running containers, but with additional options, you can view stopped, exited, or all containers.

Key Features:

• List all running containers.
• Filter by status, name, image, and ports.
• Helps in monitoring and managing containers.
• Use it to find container IDs for subsequent commands.

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Basic Syntax

docker ps [OPTIONS]

Common Options:

• -a → Show all containers (including stopped and exited ones).
• -q → Show only container IDs (useful for scripting).
• -l → Show the last created container (even if stopped).
• -n <number> → Show n most recent containers.
• --filter → Filter containers based on criteria (status, name, label, etc.).
• --format → Format the output using Go templates.
• --no-trunc → Don’t truncate the container’s output (show full IDs and names).

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Examples of docker ps

1. List All Running Containers

docker ps

This shows only the containers that are currently running.

Example Output:

CONTAINER ID   IMAGE       COMMAND      CREATED       STATUS       PORTS       NAMES
a1b2c3d4e5f6   nginx       "nginx -g…"  5 minutes ago Up 5 minutes 80/tcp     my_nginx

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2. List All Containers (Running, Stopped, and Exited)

docker ps -a

This shows all containers, including those that are stopped or exited.

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3. Show Only Container IDs

docker ps -q

Example Output:

a1b2c3d4e5f6
b2c3d4e5f678

This is useful in scripts to perform operations on multiple containers.

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4. Show the Last Created Container

docker ps -l

Displays the most recently created container, even if it has exited.

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5. Show the 3 Most Recently Created Containers

docker ps -n 3

Lists the last three created containers.

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6. Filter Containers by Status

docker ps --filter "status=exited"

This shows only containers that have exited.

Other possible status values:

• running
• paused
• restarting
• exited

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7. Filter Containers by Name

docker ps --filter "name=my_nginx"

Lists containers with names that match my_nginx.

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8. Filter Containers by Image

docker ps --filter "ancestor=nginx"

Lists all containers created from the nginx image.

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9. Display Containers with Specific Ports

docker ps --filter "publish=8080"

Lists containers that expose port 8080 on the host.

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10. Show Full Container IDs and Names

docker ps --no-trunc

Prevents truncation, showing full container IDs and names.

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11. Format the Output (--format)

docker ps --format "table {{.ID}}\t{{.Names}}\t{{.Status}}"

This customizes the output to show only container ID, name, and status in a table format.

Example Output:

CONTAINER ID   NAMES       STATUS
a1b2c3d4e5f6   my_nginx    Up 5 minutes

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12. List Containers Created in the Last 24 Hours

docker ps --filter "since=24h"

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13. Combine Filters

docker ps --filter "status=exited" --filter "ancestor=nginx"

This lists exited containers created from the nginx image.

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14. Use docker ps in a Script to Stop All Running Containers

docker stop $(docker ps -q)

This stops all currently running containers.

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15. Use docker ps to Remove All Exited Containers

docker rm $(docker ps -aq --filter "status=exited")

This removes all containers that have exited.

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Use Cases for docker ps

1. Monitoring Container Status

• Check which containers are running and their uptime.
• Ensure that critical services are active.

2. Managing Resources

• Find stopped containers and remove them to free up disk space.
• Identify paused or stuck containers for debugging.

3. Automation and Scripting

• Combine docker ps with other Docker commands (stop, rm, logs, etc.) to automate maintenance tasks.

4. Debugging and Troubleshooting

• Filter by exited containers to find failed services.
• Use --no-trunc to get detailed information about containers for in-depth analysis.

5. Security and Auditing

• Audit all running containers to ensure they are up-to-date and secure.
• Monitor containers for unauthorized or unexpected behavior.

6. Multi-Service Applications

• Quickly check the status of multiple services running in containers.
• Use docker ps to verify that each service is running on its assigned port.

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List of Common docker ps Commands

Command	Description
docker ps	List running containers
docker ps -a	List all containers
docker ps -q	Show only container IDs
docker ps -l	Show the last created container
docker ps -n 5	Show the last 5 created containers
docker ps --filter "status=running"	Show only running containers
docker ps --filter "ancestor=nginx"	List containers created from the nginx image
docker ps --no-trunc	Show full container IDs and names
docker ps --format "table {{.ID}}\t{{.Names}}"	Customize the output format

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Best Practices for Using docker ps:

1. Filter and format output for better readability and automation.
2. Monitor container status regularly to ensure services are healthy.
3. Use docker ps -q for scripting and batch operations.
4. Combine with docker logs and docker inspect for detailed troubleshooting.
5. Clean up unused containers (docker ps -a helps identify them).

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Common Errors and Solutions

1. “No such container”
   → The container may have stopped. Use docker ps -a to find it.
2. “Error response from daemon: Invalid filter”
   → Ensure the filter is valid. Check available filters with docker ps --help.
3. Command returns no output
   → There may be no running containers. Use docker ps -a to see stopped ones.

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