nix/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 `gc-reserved-space'
#
# This option specifies how much space should be reserved in normal
# use so that the garbage collector can run succesfully.  Since the
# garbage collector must perform Berkeley DB transactions, it needs
# some disk space for itself.  However, when the disk is full, this
# space is not available, so the collector would not be able to run
# precisely when it is most needed.
#
# For this reason, when Nix is run, it allocates a file
# /nix/var/nix/db/reserved of the size specified by this option.  When
# the garbage collector is run, this file is deleted before the
# Berkeley DB environment is opened.  This should give it enough room
# to proceed.
#
# The default is "1048576" (1 MiB).
#gc-reserved-space = 1048576


### 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


### Option `build-max-jobs'
#
# This option defines the maximum number of jobs that Nix will try to
# build in parallel.  The default is 1.  You should generally set it
# to the number of CPUs in your system (e.g., 2 on a Athlon 64 X2).
# It can be overriden using the `--max-jobs' / `-j' command line
# switch.
#build-max-jobs = 1


### Option `build-allow-root'
#
# This option controls Nix's behaviour when it is invoked under the
# `root' user (or setuid-root).  If `true' (default), builds are
# performed under the `root' user.  If `false', builds are performed
# under one of the users listed in the `build-users' option (see
# below).
#build-allow-root = true


### Option `build-users'
#
# This option is only applicable if `build-allow-root' is `false' and
# Nix is invoked under the `root' user (or setuid-root).  It contains
# a list of user names under which Nix can execute builds.  Builds
# cannot be performed by root since that would allow users to take
# over the system by supplying specially crafted builders; and they
# cannot be performed by the calling user since that would allow
# him/her to influence the build result.
#
# Thus this list should contain a number of `special' user accounts
# created specifically for Nix, e.g., `nix-builder-1',
# `nix-builder-2', and so on.  The more users the better, since at
# most a number of builds equal to the number of build users can be
# started.
#
# Example:
#   build-users = nix-builder-1 nix-builder-2 nix-builder-3
#build-users =


### Option `system'
#
# This option specifies the canonical Nix system name of the current
# installation, such as `i686-linux' or `powerpc-darwin'.  Nix can
# only build derivations whose `system' attribute equals the value
# specified here.  In general, it never makes sense to modify this
# value from its default, since you can use it to `lie' about the
# platform you are building on (e.g., perform a Mac OS build on a
# Linux machine; the result would obviously be wrong).  It only makes
# sense if the Nix binaries can run on multiple platforms, e.g.,
# `universal binaries' that run on `powerpc-darwin' and `i686-darwin'.
#
# It defaults to the canonical Nix system name detected by `configure'
# at build time.
#
# Example:
#   system = i686-darwin
#system =