The learning environment — questions

Every item costs minutes now and hours if skipped, because after the partition table has changed some of them can no longer be done at all.

The order within the list matters as much as the list itself. The recovery key comes first because it is the only item that cannot be produced afterwards — once a boot change has triggered a BitLocker prompt, there is no way back to it.

Points the answer must contain:

Because WSL2 sits on top of Windows and therefore inherits everything that is wrong with the Windows installation underneath it: BIOS virtualisation that is switched off, Hyper-V features disabled by a game or a VPN client, an antivirus that intercepts filesystem calls, corporate policies. Every one of those turns into a WSL2 problem that looks like a Docker problem.

The second reason is what happens when it breaks. On the native partition, Windows and Ubuntu are two independent systems: if one is broken, the other one still boots and you can keep working and hand in. With WSL2 there is only one system, and when it is broken there is no fallback left.

The goal is isolation, not Linux for its own sake: one clean identical partition instead of twenty differently misconfigured Windows installations, so that "works on my machine" stops being a category of error. macOS gives the same isolation and is equally fine. A virtual machine is a stopgap — its disk and memory overhead shows up exactly when Docker does.

Points the answer must contain:

Idempotent means: running the thing again produces the same end state as running it once. Running it a second time is not an error, and running it after a crash continues rather than breaking what already succeeded.

setup-tools.sh needs this because of arithmetic, not elegance. The first run takes over fifteen minutes and crosses a dozen independent failure sources — the network, an apt lock held by an update, a download that aborts, a mirror that is down, a full disk. Over a whole class, the run will fail somewhere. A script that could only be run from zero would then require an uninstall step nobody wrote.

So every step first asks whether the tool is already there:

The same idea returns twice more in this course, which is why it is worth learning under its name here: a Dockerfile describes a target state and is rebuilt to reach it, and Kubernetes takes a desired state and reconciles the cluster towards it. All three are the same principle — describe the end state, not the steps.

Points the answer must contain:

Because they are two different kinds of thing.

A machine state can be reached again; an identity cannot be "installed twice". Mixed into one script you get the worst of both: it asks questions in the middle of a fifteen-minute unattended run, and because of those questions nobody dares to run it a second time — which destroys exactly the idempotence the tool half depends on.

The separation also keeps the boundary around credentials clean. No credential belongs in a repository; the private SSH key is generated on the machine and never leaves it. Only the public key is uploaded to GitHub.

Points the answer must contain:

Read the error first. Almost all of them fall into three groups: the network was gone, apt was locked by a background update (Could not get lock /var/lib/dpkg/lock-frontend), or the disk is full. Each has an obvious remedy, and none of them is "start over".

Then look at what is missing and run the script again:

It continues instead of restarting, because that is what idempotent means — the steps that succeeded are detected and skipped.

Note what the run does not do: stop at the first failure. A failed step is recorded and the rest continues, so one broken download does not cost you the other eleven tools. What stayed open is listed under == Bilanz at the end, and the exit code is non-zero — read that list rather than scrolling back through fifteen minutes of output.

Two things not to do. Do not reinstall the system: an aborted script run is not a broken system. And do not put sudo in front of the whole script — it asks for elevation exactly where it needs it, and running the lot as root leaves root-owned files in your home directory, which is a second, worse problem to debug.

Points the answer must contain: