While developing my first package definition to be contributed to GNU
Guix, I followed 14.1 („Building from Git”) and 14.2 („Running
Guix Before It Is Installed”) of the manual.

14.1 suggests using a Guix environment via `guix environment guix`. I
thought it would be even better to do `guix environment --pure guix`,
and thus obtain some higher level of isolation.

I decided to continue with the environment in 14.2. Issuing

   sudo -E ./pre-inst-env guix-daemon --build-users-group=guixbuild

resulted in some error related to UID/GID. Outside the environment, it
worked, though. Inside the environment, I issued the next line from the
manual:

   ./pre-inst-env guix build hello

A massive build of various packages, including gcc, linux-libre…,
began. After a while, “sed not found” and other “not founds”
started to appear in other terminal windows (tmux panels in my case),
unrelated to the described process, and the system got impossible to
work with. After a reset, instead of the OS, I got landed in the Guile
interpreter (in kind of a debug mode, as far as I could say). It looks
like the build wiped out the store, and tomorrow’s going to be a
re-installation and reconfiguration day.

Could somebody, please, help me understand what kind of mistake I made
and what actually happened? Don’t you think it would be desirable
to mark with `[env]` the commands that should be issued inside an
environment in the manual? I find 14.2 rather confusing in this regard.
Perhaps, it would be also worthwhile to include a warning in order to
spare other newcomers a similar experience.

WŻ