nix-super/nix.conf.example

### Option `gc-keep-outputs'
#
# If `true', the garbage collector will keep the outputs of
# non-garbage derivations.  If `false' (default), outputs will be
# deleted unless they are GC roots themselves (or reachable from other
# roots).
# 
# In general, outputs must be registered as roots separately.
# However, even if the output of a derivation is registered as a root,
# the collector will still delete store paths that are used only at
# build time (e.g., the C compiler, or source tarballs downloaded from
# the network).  To prevent it from doing so, set this option to
# `true'.
gc-keep-outputs = false


### Option `gc-keep-derivations'
#
# If `true' (default), the garbage collector will keep the derivations
# from which non-garbage store paths were built.  If `false', they
# will be deleted unless explicitly registered as a root (or reachable
# from other roots).
#
# Keeping derivation around is useful for querying and traceability
# (e.g., it allows you to ask with what dependencies or options a
# store path was built), so by default this option is on.  Turn it off
# to safe a bit of disk space (or a lot if `gc-keep-outputs' is also
# turned on).
gc-keep-derivations = true


### Option `env-keep-derivations'
#
# If `false' (default), derivations are not stored in Nix user
# environments.  That is, the derivation any build-time-only
# dependencies may be garbage-collected.
#
# If `true', when you add a Nix derivation to a user environment, the
# path of the derivation is stored in the user environment.  Thus, the
# derivation will not be garbage-collected until the user environment
# generation is deleted (`nix-env --delete-generations').  To prevent
# build-time-only dependencies from being collected, you should also
# turn on `gc-keep-outputs'.
#
# The difference between this option and `gc-keep-derivations' is that
# this one is `sticky': it applies to any user environment created
# while this option was enabled, while `gc-keep-derivations' only
# applies at the moment the garbage collector is run.
env-keep-derivations = false