Common Environment Variables
Most Nix commands interpret the following environment variables:
Indicator that tells if the current environment was set up by
nix-shell. It can have the values
A colon-separated list of directories used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e.,
/home/eelco/Dev:/etc/nixos. It can be extended using the
NIX_PATHis not set at all, Nix will fall back to the following list in impure and unrestricted evaluation mode:
NIX_PATHis set to an empty string, resolving search paths will always fail. For example, attempting to use
error: file 'nixpkgs' was not found in the Nix search path
Normally, the Nix store directory (typically
/nix/store) is not allowed to contain any symlink components. This is to prevent “impure” builds. Builders sometimes “canonicalise” paths by resolving all symlink components. Thus, builds on different machines (with
/nix/storeresolving to different locations) could yield different results. This is generally not a problem, except when builds are deployed to machines where
/nix/storeresolves differently. If you are sure that you’re not going to do that, you can set
Note that if you’re symlinking the Nix store so that you can put it on another file system than the root file system, on Linux you’re better off using
bindmount points, e.g.,
$ mkdir /nix $ mount -o bind /mnt/otherdisk/nix /nix
Consult the mount 8 manual page for details.
Overrides the location of the Nix store (default
Overrides the location of the Nix static data directory (default
Overrides the location of the Nix log directory (default
Overrides the location of the Nix state directory (default
Overrides the location of the system Nix configuration directory (default
Applies settings from Nix configuration from the environment. The content is treated as if it was read from a Nix configuration file. Settings are separated by the newline character.
Overrides the location of the Nix user configuration files to load from.
The default are the locations according to the XDG Base Directory Specification. See the XDG Base Directories sub-section for details.
The variable is treated as a list separated by the
Use the specified directory to store temporary files. In particular, this includes temporary build directories; these can take up substantial amounts of disk space. The default is
This variable should be set to
daemonif you want to use the Nix daemon to execute Nix operations. This is necessary in multi-user Nix installations. If the Nix daemon's Unix socket is at some non-standard path, this variable should be set to
unix://path/to/socket. Otherwise, it should be left unset.
If set to
1, Nix will print some evaluation statistics, such as the number of values allocated.
If set to
1, Nix will print how often functions were called during Nix expression evaluation. This is useful for profiling your Nix expressions.
If Nix has been configured to use the Boehm garbage collector, this variable sets the initial size of the heap in bytes. It defaults to 384 MiB. Setting it to a low value reduces memory consumption, but will increase runtime due to the overhead of garbage collection.
XDG Base Directories
Nix follows the XDG Base Directory Specification.
For backwards compatibility, Nix commands will follow the standard only when
use-xdg-base-directories is enabled.
New Nix commands (experimental) conform to the standard by default.
The following environment variables are used to determine locations of various state and configuration files: