/tmp tmpfs is using the systemd upstream mount.

[sheenobu]

Issue description

Because of how the tmp mount is defined (it is shipped with systemd), we are unable to configure the mounting of tmpfs without disabling boot.tmpOnTmpfs and providing a custom systemd.mounts. I've been able to do this here:

https://gist.github.com/sheenobu/09947df2480e693161d3b3d83daddd49

Should the tmp.mount systemd unit be generated like above within the nixos config / https://github.com/NixOS/nixpkgs/blob/32b7b0009f168cb7e020d297c2f336ef352e9ec1/nixos/modules/system/boot/tmp.nix ?

Steps to reproduce

Enable tmpOnTmpfs.
Check systemctl cat tmp.mount.
tmp.mount is labelled as shipped with systemd and therefore not something configurable within nixos.
tmp.mount has options listed but no way to change them.

Technical details

• System: 16.03.581.e409886
• Nix version: nix-env (Nix) 1.11.2
• Nixpkgs version: 16.03.581.e409886

[andersk]

I don’t know if this has changed since the report, but it seems you can configure tmp.mount:

{
  boot.tmpOnTmpfs = true;
  systemd.mounts = [{
    where = "/tmp";
    what = "tmpfs";
    options = "1777,strictatime,nosuid,nodev,size=30%";
  }];
}

This generates an override file at /etc/systemd/system/tmp.mount.d/overrides.conf:

[Unit]

[Mount]
Options=mode=1777,strictatime,nosuid,nodev,size=30%
What=tmpfs
Where=/tmp

Perhaps the syntax could be made nicer (if systemd.mounts accepted a set with where as the key, and what were made optional, we could just write systemd.mounts."/tmp".options = "1777,strictatime,nosuid,nodev,size=30%";).

[stale]

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