Nix build directory

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1

Hi!
I am tried to override the really-heavy package (chromium) to add missing functionality (krb5). And faced with memory limitation for this operation. Then I tried to google and look in manuals and could not find any information about where does nix-build and nixos-rebuild executes genericBuild scripts for packages and how to change it. I tries to use TMDIR variable but no unpacked sources appeared there - just empty folder.

How can I move building directory from limited temporary disk to huge ssd?

2

what file system is running out of space?

/tmp should be on disk.

https://github.com/NixOS/nixpkgs/issues/54707

might gleam some issues.

3

It is hard to help ypu here without the actual expression and error…

nixdoes usually adhere to TMP, TMPDIR, and TEMP, though I am not sure in which order of precedence or whatever…

Though I can say for sure I have seen builds happening in both /tmp and /run/users/foo/tmp or what the folder was when I was in a shell already…

So, more and detailed information here might be nice.

PS: by defailt /tmp should be used which by default is on disk. So unless you changed things, there should be plenty of space…

PPS: Last month it took me an hour or two to realize that I am running out of space on /tmp because of my choice to have a 10GiB /…

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4

That is the root cause. I moved /tmp folder to tmpfs for the security reasons. Is there any way to change build directory without switching /tmp back to disk?

I try to build this package on 21.11 nixos:

  chromium_browser_krb = pkgs.chromium.browser.overrideAttrs (attrs: {
    gnFlags = lib.concatStringsSep " " [
      attrs.gnFlags
      "use_kerberos=true"
    ];
  });
  chromium_krb = pkgs.chromium.overrideAttrs (attrs: {
    browser = chromium_browser_krb;
  });

It of course may be incorrect, but I have no ability to check it because of subject.

P.S. Remount tmp with 64Gb, relaying on swap. Will see.

5

I’ve had good success with

zramSwap = {
enable = true;
algorithm = “zstd”;
};

in my configuration.nix… your mileage will vary, it will give you significantly more swap space at the cost of CPU.

You could try a symbolic link , but there must be a way to set it, which escapes me right now.

having tmp files in ram makes a lot of sense , especially with big builds. It can really keep wear and tear down of HDD’s and SSD’s… RAM has a pretty high mean time before failure… spinning rust and SSD’s are doomed to fail by their design. :wink:

6

I solved this problem by moving /tmp onto my larger disk (mv /tmp /data/tmp/) then bind mounting it back to /tmp (mount -o bind /data/tmp /tmp). Seems to have worked while in a Gnome 3 session with no ill effects (yet) but I’m definitely rebooting as soon as nixos-rebuild finishes. For me the bind mount is great because I’m rebuilding nixos and don’t want to revert my config just to move /tmp and rebuild again.

Note that if your security concerns were about data remaining on disk after deletion, using swap may carry similar risks as moving /tmp onto disk temporarily.

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