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nix help-stores

Show help about store types and their settings.

Warning

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

Synopsis

nix help-stores [option...]

Lix supports different types of stores. These are described below.

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 Lix 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 Lix 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:

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

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:

The public host key of the remote machine.

Default: empty

Whether to enable SSH compression.

Default: false

Maximum age of a connection before it is closed.

Default: 4294967295

Maximum number of concurrent connections to the Nix daemon.

Default: 1

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Default: nix-daemon

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

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

Default: empty

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

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:

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

Default: xz

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

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

Default: false

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

Default: empty

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

Default: false

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Default: empty

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

Default: false

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:

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

Default: xz

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

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

Default: false

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

Default: empty

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

Default: false

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Default: empty

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

Default: false

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:

directory where Lix will store log files.

Default: /nix/var/log/nix

Maximum age of a connection before it is closed.

Default: 4294967295

Maximum number of concurrent connections to the Nix daemon.

Default: 1

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

Physical path of the Nix store.

Default: /nix/store

Directory prefixed to all other paths.

Default: ``

Directory where Lix will store state.

Default: /dummy

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

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:

directory where Lix will store log files.

Default: /nix/var/log/nix

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Normally Lix 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

Physical path of the Nix store.

Default: /nix/store

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

Default: true

Directory prefixed to all other paths.

Default: ``

Directory where Lix will store state.

Default: /dummy

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

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 bucket.

Settings:

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

Default: 5242880

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

Default: xz

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

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

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

Default: false

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

Default: empty

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

Default: empty

Compression method for .ls files.

Default: empty

Whether to use multi-part uploads.

Default: false

Compression method for .narinfo files.

Default: empty

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

Default: false

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Default: empty

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

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

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

Default: empty

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

Default: false

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:

The public host key of the remote machine.

Default: empty

Whether to enable SSH compression.

Default: false

Maximum number of concurrent SSH connections.

Default: 1

Size of the in-memory store path metadata cache.

Default: 65536

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

Default: 0

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

Default: nix-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

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

Default: empty

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

Optional features that the system this store builds on implements (like "kvm").

Default: machine-specific

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

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

Default: false