nix-store --optimise(1)

Name

nix-store --optimise - reduce disk space usage

  Synopsis

nix-store --optimise

  Description

The operation --optimise reduces Nix store disk space usage by finding identical files in the store and hard-linking them to each other. It typically reduces the size of the store by something like 25-35%. Only regular files and symlinks are hard-linked in this manner. Files are considered identical when they have the same Nix Archive (NAR) (@docroot@/store/file-system-object/content-address.md#serial-nix-archive) serialisation: that is, regular files must have the same contents and permission (executable or non-executable), and symlinks must have the same contents.

After completion, or when the command is interrupted, a report on the achieved savings is printed on standard error.

Use -vv or -vvv to get some progress indication.

{{#include ./opt-common.md}}

{{#include ../opt-common.md}}

{{#include ../env-common.md}}

  Example

    $ nix-store --optimise
    hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
    ...
    541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
    there are 114486 files with equal contents out of 215894 files in total