This program is experimental and its interface is subject to change.
nix flake check - check whether the flake evaluates and run its tests
nix flake check [option...] flake-url
Evaluate the flake in the current directory, and build its checks:
# nix flake check
Verify that the
patchelfflake evaluates, but don't build its checks:
# nix flake check --no-build github:NixOS/patchelf
This command verifies that the flake specified by flake reference
flake-url can be evaluated successfully (as detailed below), and
that the derivations specified by the flake's
checks output can be
keep-going option is set to
true, Nix will keep evaluating as much
as it can and report the errors as it encounters them. Otherwise it will stop
at the first error.
The following flake output attributes must be derivations:
The following flake output attributes must be app definitions:
The following flake output attributes must be template definitions:
The following flake output attributes must be Nixpkgs overlays:
The following flake output attributes must be NixOS modules:
The following flake output attributes must be bundlers:
In addition, the
hydraJobs output is evaluated in the same way as
hydra-eval-jobs (i.e. as a arbitrarily deeply nested
attribute set of derivations). Similarly, the
legacyPackages.system output is evaluated like
nix-env --query --available .
Pass the value expr as the argument name to Nix functions.
Pass the string string as the argument name to Nix functions.
Start an interactive environment if evaluation fails.
The URL of the Nix store to use for evaluation, i.e. to store derivations (
.drvfiles) and inputs referenced by them.
Allow access to mutable paths and repositories.
Add path to the Nix search path. The Nix search path is initialized from the colon-separated
NIX_PATHenvironment variable, and is used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e.,
For instance, passing
-I /home/eelco/Dev -I /etc/nixos
will cause Nix to look for paths relative to
/etc/nixos, in that order. This is equivalent to setting the
NIX_PATHenvironment variable to
It is also possible to match paths against a prefix. For example, passing
-I nixpkgs=/home/eelco/Dev/nixpkgs-branch -I /etc/nixos
will cause Nix to search for
If a path in the Nix search path starts with
https://, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must consist of a single top-level directory. For example, passing
tells Nix to download and use the current contents of the
masterbranch in the
The URLs of the tarballs from the official
nixos.orgchannels (see the manual page for
nix-channel) can be abbreviated as
channel:<channel-name>. For instance, the following two flags are equivalent:
-I nixpkgs=channel:nixos-21.05 -I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz
You can also fetch source trees using flake URLs and add them to the search path. For instance,
specifies that the prefix
nixpkgsshall refer to the source tree downloaded from the
nixpkgsentry in the flake registry. Similarly,
<nixpkgs>refer to a particular branch of the
NixOS/nixpkgsrepository on GitHub.
Override the flake registries, redirecting original-ref to resolved-ref.
Commit changes to the flake's lock file.
Use the inputs of the specified flake as registry entries.
Don't allow lookups in the flake registries. This option is deprecated; use
Do not allow any updates to the flake's lock file.
Do not write the flake's newly generated lock file.
Write the given lock file instead of
flake.lockwithin the top-level flake.
Override a specific flake input (e.g.
dwarffs/nixpkgs). This implies
Recreate the flake's lock file from scratch.
Read the given lock file instead of
flake.lockwithin the top-level flake.
Update a specific flake input (ignoring its previous entry in the lock file).
Set the logging verbosity level to 'debug'.
Set the format of log output; one of
Print full build logs on standard error.
Decrease the logging verbosity level.
Increase the logging verbosity level.
Show usage information.
Disable substituters and consider all previously downloaded files up-to-date.
Set the Nix configuration setting name to value (overriding
Consider all previously downloaded files out-of-date.
During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.
Show version information.
man nix.conffor overriding configuration settings with command line flags.