06 Run commands inside a container

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Goal

Change the page nginx serves so curl localhost:8080 answers <h1>Hello from inside</h1>.

docker exec <container> <command> runs a command inside a running container — to look around, check a config file or debug a problem.

To use redirection or several commands, run them through a shell: docker exec web sh -c '…'. Without sh -c, the > would be handled by your shell, on the host.

Changes made this way live in the container's writable layer. They're gone when the container is removed — which is exactly what the next chapter is about.

Try it

Rewrite the page nginx serves, then curl it.

Go to the terminal

Hint

nginx serves /usr/share/nginx/html/index.html. docker exec web sh -c 'echo "<h1>Hello from inside</h1>" > /usr/share/nginx/html/index.html'.

Show a solution

curl localhost:8080
docker exec web sh -c 'echo "<h1>Hello from inside</h1>" > /usr/share/nginx/html/index.html'
curl localhost:8080

This interactive environment needs JavaScript. Everything you need to read is on this page, and the solution works the same way for real.

Docker

Starting Docker…