docker run

Definition

The most common Docker CLI command. It creates a brand new container from a specified image and immediately starts it.

Explain Like I'm New

The magic button to start an app. It tells Docker: 'Take this blueprint, build a box from it, and turn the box on.'

Real World Example

Typing `docker run -p 8080:80 nginx`. Docker instantly spins up a live NGINX web server on your computer, accessible on port 8080.

Common Use Cases

•Starting applications
•Testing images

Crucial `docker run` Flags

Flag	Example	Description
-d	`docker run -d nginx`	Detached mode. Runs the container safely in the background instead of freezing your terminal.
-p	`docker run -p 8080:80 nginx`	Port mapping. Maps Port 8080 on your laptop to Port 80 inside the container.
-v	`docker run -v /data:/app db`	Volume mounting. Maps a folder on your laptop's hard drive directly into the container.
--name	`docker run --name web nginx`	Assigns a custom, human-readable name to the container instead of a random hash.
-e	`docker run -e DB_PASS=123 db`	Environment variables. Passes secret passwords or configs directly into the running container.

Interview Questions

basic

What does the `-d` flag do when using `docker run`?

intermediate

What is the difference between `docker create` and `docker run`?

Flash Cards

Question

What does -d do?

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Answer

Detached mode. It starts the container running silently in the background, giving you your terminal prompt back. (Without it, the container's logs take over your screen).

Question

Create vs Run?

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Answer

`docker create` prepares the container but leaves it dormant (Stopped). `docker run` creates the container AND instantly starts it. (`docker run` = `create` + `start`).