# Too many links Error in the Nix store

Symptom: when building something, you get an error message such as

    ...
    mkdir: cannot create directory `/nix/store/name': Too many links

This is usually because you have more than 32,000 subdirectories in `/nix/store`, as can be seen using `ls -l`:

    $ ls -ld /nix/store
    drwxrwxrwt 32000 nix nix 4620288 Sep 8 15:08 store

The `ext2` file system is limited to an inode link count of 32,000 (each subdirectory increasing the count by one). Furthermore, the `st_nlink` field of the `stat` system call is a 16-bit value.

This only happens on very large Nix installations (such as build machines).

Quick solution: run the garbage collector. You may want to use the `--max-links` option.

Real solution: put the Nix store on a file system that supports more than 32,000 subdirectories per directory, such as ext4. (This doesn’t solve the `st_nlink` limit, but ext4 lies to the kernel by reporting a link count of 1 if it exceeds the limit.)