-sh-3.2# df -h
Filesystem        Size    Used   Avail Capacity iused ifree %iused  Mounted on
/dev/disk3s3s1   228Gi    11Gi    20Gi    37%    453k  213M    0%   /
devfs            204Ki   204Ki     0Bi   100%     706     0  100%   /dev
/dev/disk3s6     228Gi   2.0Gi    20Gi     9%       2  213M    0%   /System/Volumes/VM
/dev/disk3s4     228Gi    14Gi    20Gi    42%    5.4k  213M    0%   /System/Volumes/Preboot
/dev/disk3s2     228Gi    59Mi    20Gi     1%      69  213M    0%   /System/Volumes/Update
/dev/disk1s2     500Mi   6.0Mi   483Mi     2%       3  4.9M    0%   /System/Volumes/xarts
/dev/disk1s1     500Mi   5.7Mi   483Mi     2%      30  4.9M    0%   /System/Volumes/iSCPreboot
/dev/disk1s3     500Mi   916Ki   483Mi     1%      32  4.9M    0%   /System/Volumes/Hardware
/dev/disk3s1     228Gi    95Gi    20Gi    83%    2.2M  213M    1%   /System/Volumes/Data
map auto_home      0Bi     0Bi     0Bi   100%       0     0     -   /System/Volumes/Data/home
/dev/disk3s7     228Gi    82Gi    20Gi    81%    4.7M  213M    2%   /nix
/dev/disk4       512Mi    12Mi   500Mi     3%       4  4.3G    0%   /private/var/run/agenix.d

    gc = {
      automatic = true;
      interval = [
        {
          Minute = 15;
        }
        {
          Minute = 45;
        }
      ];
      # ensure up to 100G free space every half hour
      options = "--max-freed $(df -k /nix/store | awk 'NR==2 {available=$4; required=100*1024*1024; to_free=required-available; printf \"%.0d\", to_free*1024}')";
    };

   log erase [--all] [--ttl] ?

nix = {
    linux-builder = {
      enable = true;
      config =
        {
          virtualisation = {
            darwin-builder = {
              diskSize = 80 * 1024;
              memorySize = 12 * 1024;
            };
            cores = 8;
          };
        };
    };
  };