Warning
This program is experimental and its interface is subject to change.

Name

nix help-stores - show help about store types and their settings

Synopsis

nix help-stores [option...]

Nix supports different types of stores:

Store URL format

Stores are specified using a URL-like syntax. For example, the command

# nix path-info --store https://cache.nixos.org/ --json \
  /nix/store/a7gvj343m05j2s32xcnwr35v31ynlypr-coreutils-9.1

fetches information about a store path in the HTTP binary cache located at https://cache.nixos.org/, which is a type of store.

Store URLs can specify store settings using URL query strings, i.e. by appending ?name1=value1&name2=value2&... to the URL. For instance,

--store ssh://machine.example.org?ssh-key=/path/to/my/key

tells Nix to access the store on a remote machine via the SSH protocol, using /path/to/my/key as the SSH private key. The supported settings for each store type are documented below.

The special store URL auto causes Nix to automatically select a store as follows:

Dummy Store

Store URL format: dummy://

This store type represents a store that contains no store paths and cannot be written to. It's useful when you want to use the Nix evaluator when no actual Nix store exists, e.g.

# nix eval --store dummy:// --expr '1 + 2'

Settings

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

Experimental SSH Store with filesytem mounted

Warning

This store is part of an experimental feature.

To use this store, make sure the mounted-ssh-store experimental feature is enabled. For example, include the following in nix.conf:

extra-experimental-features = mounted-ssh-store

Store URL format: mounted-ssh-ng://[username@]hostname

Experimental store type that allows full access to a Nix store on a remote machine, and additionally requires that store be mounted in the local file system.

The mounting of that store is not managed by Nix, and must by managed manually. It could be accomplished with SSHFS or NFS, for example.

The local file system is used to optimize certain operations. For example, rather than serializing Nix archives and sending over the Nix channel, we can directly access the file system data via the mount-point.

The local file system is also used to make certain operations possible that wouldn't otherwise be. For example, persistent GC roots can be created if they reside on the same file system as the remote store: the remote side will create the symlinks necessary to avoid race conditions.

Settings

  • base64-ssh-public-host-key

    The public host key of the remote machine.

    Default: empty

  • compress

    Whether to enable SSH compression.

    Default: false

  • log

    directory where Nix will store log files.

    Default: /nix/var/log/nix

  • max-connection-age

    Maximum age of a connection before it is closed.

    Default: 4294967295

  • max-connections

    Maximum number of concurrent connections to the Nix daemon.

    Default: 1

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • real

    Physical path of the Nix store.

    Default: /nix/store

  • remote-program

    Path to the nix-daemon executable on the remote machine.

    Default: nix-daemon

  • remote-store

    Store URL to be used on the remote machine. The default is auto (i.e. use the Nix daemon or /nix/store directly).

    Default: empty

  • root

    Directory prefixed to all other paths.

    Default: ``

  • ssh-key

    Path to the SSH private key used to authenticate to the remote machine.

    Default: empty

  • state

    Directory where Nix will store state.

    Default: /dummy

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

Experimental SSH Store

Store URL format: ssh-ng://[username@]hostname

Experimental store type that allows full access to a Nix store on a remote machine.

Settings

  • base64-ssh-public-host-key

    The public host key of the remote machine.

    Default: empty

  • compress

    Whether to enable SSH compression.

    Default: false

  • max-connection-age

    Maximum age of a connection before it is closed.

    Default: 4294967295

  • max-connections

    Maximum number of concurrent connections to the Nix daemon.

    Default: 1

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • remote-program

    Path to the nix-daemon executable on the remote machine.

    Default: nix-daemon

  • remote-store

    Store URL to be used on the remote machine. The default is auto (i.e. use the Nix daemon or /nix/store directly).

    Default: empty

  • ssh-key

    Path to the SSH private key used to authenticate to the remote machine.

    Default: empty

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

HTTP Binary Cache Store

Store URL format: http://..., https://...

This store allows a binary cache to be accessed via the HTTP protocol.

Settings

  • compression

    NAR compression method (xz, bzip2, gzip, zstd, or none).

    Default: xz

  • compression-level

    The preset level to be used when compressing NARs. The meaning and accepted values depend on the compression method selected. -1 specifies that the default compression level should be used.

    Default: -1

  • index-debug-info

    Whether to index DWARF debug info files by build ID. This allows dwarffs to fetch debug info on demand

    Default: false

  • local-nar-cache

    Path to a local cache of NARs fetched from this binary cache, used by commands such as nix store cat.

    Default: empty

  • parallel-compression

    Enable multi-threaded compression of NARs. This is currently only available for xz and zstd.

    Default: false

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • secret-key

    Path to the secret key used to sign the binary cache.

    Default: empty

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

  • write-nar-listing

    Whether to write a JSON file that lists the files in each NAR.

    Default: false

Local Binary Cache Store

Store URL format: file://path

This store allows reading and writing a binary cache stored in path in the local filesystem. If path does not exist, it will be created.

For example, the following builds or downloads nixpkgs#hello into the local store and then copies it to the binary cache in /tmp/binary-cache:

# nix copy --to file:///tmp/binary-cache nixpkgs#hello

Settings

  • compression

    NAR compression method (xz, bzip2, gzip, zstd, or none).

    Default: xz

  • compression-level

    The preset level to be used when compressing NARs. The meaning and accepted values depend on the compression method selected. -1 specifies that the default compression level should be used.

    Default: -1

  • index-debug-info

    Whether to index DWARF debug info files by build ID. This allows dwarffs to fetch debug info on demand

    Default: false

  • local-nar-cache

    Path to a local cache of NARs fetched from this binary cache, used by commands such as nix store cat.

    Default: empty

  • parallel-compression

    Enable multi-threaded compression of NARs. This is currently only available for xz and zstd.

    Default: false

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • secret-key

    Path to the secret key used to sign the binary cache.

    Default: empty

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

  • write-nar-listing

    Whether to write a JSON file that lists the files in each NAR.

    Default: false

Local Daemon Store

Store URL format: daemon, unix://path

This store type accesses a Nix store by talking to a Nix daemon listening on the Unix domain socket path. The store pseudo-URL daemon is equivalent to unix:///nix/var/nix/daemon-socket/socket.

Settings

  • log

    directory where Nix will store log files.

    Default: /nix/var/log/nix

  • max-connection-age

    Maximum age of a connection before it is closed.

    Default: 4294967295

  • max-connections

    Maximum number of concurrent connections to the Nix daemon.

    Default: 1

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • real

    Physical path of the Nix store.

    Default: /nix/store

  • root

    Directory prefixed to all other paths.

    Default: ``

  • state

    Directory where Nix will store state.

    Default: /dummy

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

Local Store

Store URL format: local, root

This store type accesses a Nix store in the local filesystem directly (i.e. not via the Nix daemon). root is an absolute path that is prefixed to other directories such as the Nix store directory. The store pseudo-URL local denotes a store that uses / as its root directory.

A store that uses a root other than / is called a chroot store. With such stores, the store directory is "logically" still /nix/store, so programs stored in them can only be built and executed by chroot-ing into root. Chroot stores only support building and running on Linux when mount namespaces and user namespaces are enabled.

For example, the following uses /tmp/root as the chroot environment to build or download nixpkgs#hello and then execute it:

# nix run --store /tmp/root nixpkgs#hello
Hello, world!

Here, the "physical" store location is /tmp/root/nix/store, and Nix's store metadata is in /tmp/root/nix/var/nix/db.

It is also possible, but not recommended, to change the "logical" location of the Nix store from its default of /nix/store. This makes it impossible to use default substituters such as https://cache.nixos.org/, and thus you may have to build everything locally. Here is an example:

# nix build --store 'local?store=/tmp/my-nix/store&state=/tmp/my-nix/state&log=/tmp/my-nix/log' nixpkgs#hello

Settings

  • log

    directory where Nix will store log files.

    Default: /nix/var/log/nix

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • read-only

    Allow this store to be opened when its database is on a read-only filesystem.

    Normally Nix will attempt to open the store database in read-write mode, even for querying (when write access is not needed), causing it to fail if the database is on a read-only filesystem.

    Enable read-only mode to disable locking and open the SQLite database with the immutable parameter set.

    Warning Do not use this unless the filesystem is read-only.

    Using it when the filesystem is writable can cause incorrect query results or corruption errors if the database is changed by another process. While the filesystem the database resides on might appear to be read-only, consider whether another user or system might have write access to it.

    Default: false

  • real

    Physical path of the Nix store.

    Default: /nix/store

  • require-sigs

    Whether store paths copied into this store should have a trusted signature.

    Default: true

  • root

    Directory prefixed to all other paths.

    Default: ``

  • state

    Directory where Nix will store state.

    Default: /dummy

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

S3 Binary Cache Store

Store URL format: s3://bucket-name

This store allows reading and writing a binary cache stored in an AWS S3 (or S3-compatible service) bucket. This store shares many idioms with the HTTP Binary Cache Store.

For AWS S3, the binary cache URL for a bucket named example-nix-cache will be exactly s3://example-nix-cache. For S3 compatible binary caches, consult that cache's documentation.

Anonymous reads to your S3-compatible binary cache

If your binary cache is publicly accessible and does not require authentication, it is simplest to use the [HTTP Binary Cache Store] rather than S3 Binary Cache Store with https://example-nix-cache.s3.amazonaws.com instead of s3://example-nix-cache.

Your bucket will need a bucket policy like the following to be accessible:

{
    "Id": "DirectReads",
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowDirectReads",
            "Action": [
                "s3:GetObject",
                "s3:GetBucketLocation"
            ],
            "Effect": "Allow",
            "Resource": [
                "arn:aws:s3:::example-nix-cache",
                "arn:aws:s3:::example-nix-cache/*"
            ],
            "Principal": "*"
        }
    ]
}

Authentication

Nix will use the default credential provider chain for authenticating requests to Amazon S3.

Note that this means Nix will read environment variables and files with different idioms than with Nix's own settings, as implemented by the AWS SDK. Consult the documentation linked above for further details.

Authenticated reads to your S3 binary cache

Your bucket will need a bucket policy allowing the desired users to perform the s3:GetObject and s3:GetBucketLocation action on all objects in the bucket. The anonymous policy given above can be updated to have a restricted Principal to support this.

Authenticated writes to your S3-compatible binary cache

Your account will need an IAM policy to support uploading to the bucket:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "UploadToCache",
      "Effect": "Allow",
      "Action": [
        "s3:AbortMultipartUpload",
        "s3:GetBucketLocation",
        "s3:GetObject",
        "s3:ListBucket",
        "s3:ListBucketMultipartUploads",
        "s3:ListMultipartUploadParts",
        "s3:PutObject"
      ],
      "Resource": [
        "arn:aws:s3:::example-nix-cache",
        "arn:aws:s3:::example-nix-cache/*"
      ]
    }
  ]
}

Examples

With bucket policies and authentication set up as described above, uploading works via nix copy (experimental).

  • To upload with a specific credential profile for Amazon S3:

    $ nix copy nixpkgs.hello \
  --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2'

  • To upload to an S3-compatible binary cache:

    $ nix copy nixpkgs.hello --to \
  's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com'

Settings

  • buffer-size

    Size (in bytes) of each part in multi-part uploads.

    Default: 5242880

  • compression

    NAR compression method (xz, bzip2, gzip, zstd, or none).

    Default: xz

  • compression-level

    The preset level to be used when compressing NARs. The meaning and accepted values depend on the compression method selected. -1 specifies that the default compression level should be used.

    Default: -1

  • endpoint

    The URL of the endpoint of an S3-compatible service such as MinIO. Do not specify this setting if you're using Amazon S3.

    Note

    This endpoint must support HTTPS and will use path-based addressing instead of virtual host based addressing.

    Default: empty

  • index-debug-info

    Whether to index DWARF debug info files by build ID. This allows dwarffs to fetch debug info on demand

    Default: false

  • local-nar-cache

    Path to a local cache of NARs fetched from this binary cache, used by commands such as nix store cat.

    Default: empty

  • log-compression

    Compression method for log/* files. It is recommended to use a compression method supported by most web browsers (e.g. brotli).

    Default: empty

  • ls-compression

    Compression method for .ls files.

    Default: empty

  • multipart-upload

    Whether to use multi-part uploads.

    Default: false

  • narinfo-compression

    Compression method for .narinfo files.

    Default: empty

  • parallel-compression

    Enable multi-threaded compression of NARs. This is currently only available for xz and zstd.

    Default: false

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • profile

    The name of the AWS configuration profile to use. By default Nix will use the default profile.

    Default: empty

  • region

    The region of the S3 bucket. If your bucket is not in us–east-1, you should always explicitly specify the region parameter.

    Default: us-east-1

  • scheme

    The scheme used for S3 requests, https (default) or http. This option allows you to disable HTTPS for binary caches which don't support it.

    Note

    HTTPS should be used if the cache might contain sensitive information.

    Default: empty

  • secret-key

    Path to the secret key used to sign the binary cache.

    Default: empty

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

  • write-nar-listing

    Whether to write a JSON file that lists the files in each NAR.

    Default: false

SSH Store

Store URL format: ssh://[username@]hostname

This store type allows limited access to a remote store on another machine via SSH.

Settings

  • base64-ssh-public-host-key

    The public host key of the remote machine.

    Default: empty

  • compress

    Whether to enable SSH compression.

    Default: false

  • max-connections

    Maximum number of concurrent SSH connections.

    Default: 1

  • path-info-cache-size

    Size of the in-memory store path metadata cache.

    Default: 65536

  • priority

    Priority of this store when used as a substituter. A lower value means a higher priority.

    Default: 0

  • remote-program

    Path to the nix-store executable on the remote machine.

    Default: nix-store

  • remote-store

    Store URL to be used on the remote machine. The default is auto (i.e. use the Nix daemon or /nix/store directly).

    Default: empty

  • ssh-key

    Path to the SSH private key used to authenticate to the remote machine.

    Default: empty

  • store

    Logical location of the Nix store, usually /nix/store. Note that you can only copy store paths between stores if they have the same store setting.

    Default: /nix/store

  • system-features

    Optional system features available on the system this store uses to build derivations.

    Example: "kvm"

    Default: machine-specific

  • trusted

    Whether paths from this store can be used as substitutes even if they are not signed by a key listed in the trusted-public-keys setting.

    Default: false

  • want-mass-query

    Whether this store can be queried efficiently for path validity when used as a substituter.

    Default: false

Options

  • --debug

    Set the logging verbosity level to 'debug'.

  • --log-format format

    Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

  • --print-build-logs / -L

    Print full build logs on standard error.

  • --quiet

    Decrease the logging verbosity level.

  • --verbose / -v

    Increase the logging verbosity level.

Miscellaneous global options

  • --help

    Show usage information.

  • --offline

    Disable substituters and consider all previously downloaded files up-to-date.

  • --option name value

    Set the Nix configuration setting name to value (overriding nix.conf).

  • --refresh

    Consider all previously downloaded files out-of-date.

  • --version

    Show version information.

Note

See man nix.conf for overriding configuration settings with command line flags.