NOTES

NOTES

Notes for my blog post

Things Docker does right!
- When you modify a script that is run Docker realises it is different
  and will rewind its state back to the point where the ADD command for that
  script occurred and then re-run from there. This is important!

- Put all the long running, annoying, downloads at the beginning.

- Add lots of little script files.
- Add script files ONE AT A TIME. This way if you have add a new one then
  it won't force a rebuild.

- The original build script had to do things like check whether something
  was installed or not. Sanity checks basically. You no longer need to do this!
  You know EXACTLY what state it's going to be in.

  You can "docker run -it <image> bash" to have a look at the state at any
  point of the install process.

- Unfortunately, docker can't know ... really it can't ... whether
  adding an "ADD ..." command somewhere in the middle of a list of already
  performed commands will affect those later on or not. It has to assume it
  will. This is why you have to build the Dockerfile incrementally in a
  somewhat careful way.