Local Store - Nix 2.34.9 Reference Manual

Source: /pages/nix-manual/store/types/local-store

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

• build-dir The directory on the host, in which derivations' temporary build directories are created. If not set, Nix will use the builds subdirectory of its configured state directory. Note that builds are often performed by the Nix daemon, so its build-dir applies. Nix will create this directory automatically with suitable permissions if it does not exist. Otherwise its permissions must allow all users to traverse the directory (i.e. it must have o+x set, in unix parlance) for non-sandboxed builds to work correctly. This is also the location where --keep-failed leaves its files. If Nix runs without sandbox, or if the platform does not support sandboxing with bind mounts (e.g. macOS), then the builder's environment will contain this directory, instead of the virtual location sandbox-build-dir.

Warning build-dir must not be set to a world-writable directory. Placing temporary build directories in a world-writable place allows other users to access or modify build data that is currently in use. This alone is merely an impurity, but combined with another factor this has allowed malicious derivations to escape the build sandbox.

See also the global build-dir setting. Default: ``

• ignore-gc-delete-failure

Warning This setting is part of an experimental feature. To change this setting, make sure the local-overlay-store experimental feature is enabled. For example, include the following in nix.conf: extra-experimental-features = local-overlay-store ignore-gc-delete-failure = ...

Whether to ignore failures when deleting items with the garbage collector. Normally the garbage collector will fail with an error if the nix daemon cannot delete a file, with this setting such errors will only be printed as warnings. Default: false

• log directory where Nix stores 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 attempts 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 stores 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
• use-roots-daemon

Warning This setting is part of an experimental feature. To change this setting, make sure the local-overlay-store experimental feature is enabled. For example, include the following in nix.conf: extra-experimental-features = local-overlay-store use-roots-daemon = ...

Whether to request garbage collector roots from an external daemon. When enabled, the garbage collector connects to a Unix domain socket at <state-dir>/gc-roots-socket/socket to discover additional roots that should not be collected. This is useful when the Nix daemon runs without root privileges and cannot scan /proc for runtime roots. The daemon can be started with nix store roots-daemon. Default: false

• want-mass-query Whether this store can be queried efficiently for path validity when used as a substituter. Default: false

nix.dev/manual/nix/stable/store/types/local-store.html