Run Command When Container Starts

Create Dockerfile

You can use ENTRYPOINT and CMD to run a command when a container starts. ENTRYPOINT defines the program to run while CMD defines the argument to pass. Note that if ENTRYPOINT is not defined, CMD will send commands to /bin/sh -c

# Build from base image
FROM ubuntu:latest

# Maintainer label
LABEL maintainer="[email protected]"

# Ping Google.com five times
ENTRYPOINT ["/bin/echo"]
CMD ["Hello", "World"]

Build Image From Dockerfile

Build the Dockerfile (docker build) in the current directory (.) and call the image chrisalbon/ubuntu:hello-world (--tag chrisalbon/ubuntu:hello-world).

docker build --tag chrisalbon/ubuntu:hello-world .
Sending build context to Docker daemon  2.048kB
Step 1/4 : FROM ubuntu:latest
 ---> 1e4467b07108
Step 2/4 : LABEL maintainer="[email protected]"
 ---> Using cache
 ---> 74a6f636b9c1
Step 3/4 : ENTRYPOINT ["/bin/echo"]
 ---> Running in d43915bb2075
Removing intermediate container d43915bb2075
 ---> b7c93aeb23d0
Step 4/4 : CMD ["Hello", "World"]
 ---> Running in 9dc2e4b32004
Removing intermediate container 9dc2e4b32004
 ---> b1ef4c66453f
Successfully built b1ef4c66453f
Successfully tagged chrisalbon/ubuntu:hello-world

Run Docker Container From Image

Start and create (docker run) an interative (-it) Docker container from the image called chrisalbon/ubuntu:hello-world. Remove the container after it stops (-rm)

docker run --rm -it chrisalbon/ubuntu:hello-world
Hello World