Docker, and why containers exist at all
By the end of today you can explain what a container actually is, write a Dockerfile that is not wasteful, and say why a container is not a virtual machine.
YesterdayOn Day 9 you isolated Python packages so two projects could not interfere. A container isolates everything else too.
TomorrowTomorrow, the pipeline that builds and ships those containers automatically.
Why this matters
Containers are how nearly all software is shipped now. The isolation idea is the same one you met with virtual environments on Day 9, applied to the entire operating environment.
- Containers
- Images and layers
- Dockerfiles
- Containers against VMs
Learn it
80 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
4 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
50 minContainerise your API. Write a Dockerfile with the instructions deliberately in a bad order, build it, change one line of application code and rebuild, timing it. Then reorder so dependencies are installed before code is copied, and rebuild after another code change. Compare the times.
Recall it
20 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
5 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01A container is a restricted process, not a small virtual machine
- 02An image is the template; a container is the running instance
- 03Layer order decides whether a code change reinstalls your dependencies
- 04Anything written inside disappears unless it is in a volume
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.