Permanently use a sandbox build directory outside of /tmp?

johanneskastl · March 3, 2025, 12:23pm

Opened a bug report at home-manager to clarify why the TMPDIR=/var/tmp/ is needed…

bug: home-manager not respecting build-dir when set in /etc/nix/nix.conf?

opened 10:09AM - 02 Mar 25 UTC

bug triage

### Are you following the right branch? - [x] My Nixpkgs and Home Manager versi…ons are in sync ### Is there an existing issue for this? - [x] I have searched the existing issues ### Issue description Dear maintainers, as discussed in https://discourse.nixos.org/t/permanently-use-a-sandbox-build-directory-outside-of-tmp/60353/, I am using home-manager on a Fedora-based device with only 8GB of RAM. Hence the `tmpfs` in `/tmp` is too small, while `/var/tmp/` has enough space. Setting `build-dir` in `/etc/nix/nix.conf` (or `/etc/nix/nix.custom.conf`) shows this setting when running `nix config show`: ``` $ nix config show|grep build-dir build-dir = /var/tmp sandbox-build-dir = /build ``` (As far as I found this obseletes setting the TMPDIR variable in the nix-daemon systemd unit file) However, when using `home-manager`, I always need to prefix the command with `TMPDIR=/var/tmp/`, otherwise the build fails due to missing space in `/tmp`. ``` # working $ nix-channel --update && TMPDIR=/var/tmp/ home-manager switch # failing $ nix-channel --update && home-manager switch $ ``` I searched a lot on how to set this in the home-manager configuration itself somewhere, but of course those are lousy search terms so I might just have missed it. Is there an option that I need to set so this is being respected? Or is this a bug that needs to be fixed? Thanks in advance! Kind Regards, Johannes ### Maintainer CC _No response_ ### System information ```markdown - system: `"x86_64-linux"` - host os: `Linux 6.12.10-200.fc41.x86_64, Aurora, 41.20250302 (Kinoite), ddd565a` - multi-user?: `yes` - sandbox: `yes` - version: `nix-env (Nix) 2.26.1` - nixpkgs: `/nix/store/w3ghsxcwcynh88fgr7j841drw08fyzn0-nixpkgs-24.11/nixpkgs` ```