Running Your First Containers with Docker

Example 1: Whalesay Container

1. Run the Whalesay container: Execute the following command in your terminal or command prompt:

docker run docker/whalesay cowsay "Hey Team! 👋"

This command will pull the public whalesay image from Docker Hub, download it, and run a container with the custom command provided.

2. View the output: After the container finishes running, you should see an ASCII art output with the custom phrase "Hey Team! 👋".

 ________________
< Hey Team! 👋 >
 ----------------
    \
     \
      \
                    ##        .
              ## ## ##       ==
           ## ## ## ##      ===
       /""""""""""""""""___/ ===
  ~~~ {~~ ~~~~ ~~~ ~~~~ ~~ ~ /  ===- ~~~
       \______ o          __/
        \    \        __/
          \____\______/

Example 2: Postgres Container

1. Run the Postgres container: Execute the following command in your terminal or command prompt:

docker run -e POSTGRES_PASSWORD=foobarbaz -p 5432:5432 postgres:15.1-alpine

This command will:

• Set the POSTGRES_PASSWORD environment variable (required for the container to start)
• Publish port 5432 on your localhost and connect it to port 5432 inside the container
• Pull the postgres:15.1-alpine image from Docker Hub, if it's not already available locally
• Start the container, creating a running Postgres 15.1 instance on the Alpine operating system

2. Verify the Postgres container is running: Open a PostgreSQL client such as pgAdmin and connect to the database by adding a new server with the following information:

   - Host: localhost
   - Port: 5432
   - User: postgres
   - Password: foobarbaz

3. Execute a query: Run a sample query to confirm the connection and access to the database inside the container. For example:

SELECT * FROM information_schema.tables;

This query will return all the tables from the information schema within the database running inside the container.