When containers run, the Build layers are Read Only but there’s a Writable layer that gets written to. This is done via the Union File System using Copy on Write.
Note: container does not contain a kernel. It uses the host’s kernel.
Lifecycle like a VM.
Modernize traditional apps: lift and shift small part of existing app first
Ephemeral (don’t hang around for years) and immutable (we don’t login and fix).
docker container run -it alpine sh
To exit shell,
Ctrl p q
Note: if you’d like Docker to automatically clean up the container and remove the file system when the container exits, you can add the
docker container stop <first few digits of id>
Re first few digits: we should need enough to be unique.
Note: Docker gives the container 10 seconds to clean up before stopping it.
To see container, we can use:
docker container ls or
(and use the
-a flag to see stopped containers).
docker container start <first few digits of id>
Default processes for new containers
CMD: run-time arguments override CMD instructions
ENTRYPOINT: run-time arguments are appended to ENTRYPOINT