# rm -rf /
rm: it is dangerous to operate recursively on '/'
rm: use --no-preserve-root to override this failsafe
There's still lots of ways to screw up a rm, like "rm -rf /*" or deleting your entire home directory, but a space after the initial / was apparently common enough that they eventually put a big failsafe for that in the GNU version.
I don't recall which one it is (u for unset perhaps?) but I cover this by starting every (bash, E and pipefail are not POSIX) script with `set -eEuo pipefail`. All should be the default IMO, I don't understand - other than back-compat - why you wouldn't want them.
You can also prevent this by never using $VAR, and instead always using ${VAR:?} to exit with error if VAR is unset (or use one of the other options to provide a default).
