chapter 2:

• docker run IMAGE
  • starts a container from an application package
  • if it cannot find the package locally it will download it
  • it will also run the application in the container it started
• image: a container package
• rerunning the same container will often result in it having different names and ip's
• container
  • an isolated box within the same computer
  • isolated in the sense that it has its own virtual env like hostname ip and disk
  • this virtual env is managed by docker
• density: running as many apps on a machine as possible to fully utilize its resources
• density conflicts with isolation
• VM's (container's predecessor) were also boxes
  • they were bulkier boxes each VM instance having its own OS
• Containers use the machines' OS instead of having their own, they end up being leaner and more efficient
• docker run --interactive --tty IMAGE
  • interactive: set up a connection to a container
  • tty: connect to a terminal session inside the container
• docker container ls
  • lists running containers
  • container ID should match the machine's hostname
  • --all shows all containers even stopped and exited ones
    • exited container don't use up memory or cpu but do use up disk space, they don't get removed unless you remove them
• docker container top CONTAINERID: same as top when connected to a machine (shows whats runnning in the continer)
• docker container logs CONTAINER-ID
• docker container inspect - details of a container, usefull for debugging
• containers are exited once the application procss ends they don't keep running by themselves
• docker run --detach --publish 8088:80 IMAGE
  • run a container in the background
  • container's port 80 goes to your machines port 8088
• how containers' IP work:
  • Docker creates and manages a virtual network
  • it injects itself into the computer's network layer
  • nothing besides docker can directly access this virtual network
  • publishing it a port makes it acciessible
• docker container states CONTAINER-ID - shows cpu, memory, network I/O
• docker container rm --force - remove any containers even if they are running
• docker container rm --force $(docker container ls --all --quiet) - tidy up and close any container still running at eod
• docker cli -> docker api -> docker engine -> containerd -> OS
  • the api isn't always your machine, could be a remote machine
  • containerd: open source component overseen by the CNCF and OCI
• CNCF: cloud native computing foundation
• OCI: open container initiative

Lab:

• can't use interactive mode with web app containers
• docker container exec CONT-ID ls PATH - runs ls on the path inside the container
• docker container cp LOCAL-FILE-NAME CONT-ID:/PATH/FILE-NAME - copies a local file into the running container