JMM’s

Notes on Nix/NixOS

A mutable page about an immutable package manager.

I should probably split this into separate pages. There’s Nix the language, Nix the package manager, nixpkgs the list of packages, and NixOS the operating system. There’s also nix flakes, which I haven’t used too much yet.

Nix allows you to do cool things like:

I got into Nix because I would read John Wiegley’s personal .emacs configuration. He used to use git submodules to manage his complex Emacs dependencies, and then one day I noticed he switched to this thing called Nix. I first used Nix to also manage Emacs stuff (on Debian), then I eventually switched to NixOS.

Command Line stuff

This section might already be out of date, since some arguments have changed.

Start a Nix REPL with specific channel

nix repl -I nixpkgs=channel:nixos-unstable "<nixpkgs>"

These arguments may change later. You can also use specific channels like nixos-21.11

NixOS configuration REPL

nix repl "<nixpkgs/nixos>"

You can look at configured variables under the config set. For example: config.networking.hostName will say your configured hostname.

Build and install package from channel

Here’s one way to install the latest yt-dlp: 

nix build -f channel:nixos-unstable yt-dlp

This just builds (or usually just fetches) the derivation and stores the result in “./result” in the current directory. You can then install it with: 

nix-env -i ./result

This is pretty imperative, and some would argue that a more proper thing to do would be to manage this in either your NixOS config or Home Manager. I won’t argue that. Sometimes upgrading all packages breaks them in weird ways. This might be fixed by Flakes.

Garbage collect old NixOS system profiles

As root (e.g. using sudo) run: 

nix-env --list-generations --profile /nix/var/nix/profiles/system

To get a list of NixOS system generations. Then run: 

nix-env --delete-generations +1 --profile /nix/var/nix/profiles/system --dry-run

to delete everything except your current generation. Of course, you’d do this without the --dry-run argument. You can also supply specific generation numbers instead of +1.

To-Dos

Errors

Some documentation for some errors I’ve encountered, as I’ve encountered them.

Bus error while rebuilding NixOS

Encountered on 2023-12-07

Trying to finally upgrade to 23.11. I’m getting the following error while building: 

building '/nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv'...
unpacking sources
unpacking source archive /nix/store/n5s7zab7lp7y162lwakk3k6qvpzis6sf-xwayland-23.2.2.tar.xz
source root is xwayland-23.2.2
setting SOURCE_DATE_EPOCH to timestamp 1698198775 of file xwayland-23.2.2/xserver.ent.in
patching sources
updateAutotoolsGnuConfigScriptsPhase
configuring
mesonConfigurePhase flags: --prefix=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2 --libdir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/lib --libexecdir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/libexec --bindir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/bin --sbindir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/sbin --includedir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/include --mandir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/share/man --infodir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/share/info --localedir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/share/locale -Dauto_features=enabled -Dwrap_mode=nodownload --buildtype=plain -Dxwayland_eglstream=true -Dxcsecurity=true -Ddefault_font_path=/run/current-system/sw/share/X11/fonts -Dxkb_bin_dir=/nix/store/jlzjj0yn56pzgs5cwd69a335gb213sds-xkbcomp-1.4.6/bin -Dxkb_dir=/nix/store/w4m1s9q2hlisl2bbhxmlwmci1m7nxzdr-xkeyboard-config-2.40/etc/X11/xkb -Dxkb_output_dir=/nix/store/hg13f7gy7671hs6mwz5r39swlsav5iay-xwayland-23.2.2/share/X11/xkb/compiled -Dlibunwind=true
/nix/store/qrmvf49dbs7yqshymnqdhaiig0mcljlz-meson-1.2.3/nix-support/setup-hook: line 3:    25 Bus error               (core dumped) meson setup build "${flagsArray[@]}"
error: builder for '/nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv' failed with exit code 135
error: 1 dependencies of derivation '/nix/store/b6bl6r130285xkwvwvjl17a9zain90dv-man-paths.drv' failed to build
error: 1 dependencies of derivation '/nix/store/b4dm5ika5kya4z9g2mh60986i33vz9ff-system-path.drv' failed to build
error: 1 dependencies of derivation '/nix/store/aaj3m75x9czpxgblzb8cw1755jvgwcks-X-Restart-Triggers-polkit.drv' failed to build
error: 1 dependencies of derivation '/nix/store/r9y9ci2i9fw22qg6amvp8q9f78294vhz-dbus-1.drv' failed to build
error: 1 dependencies of derivation '/nix/store/09bjggsj8fpnym3rfvf9g0kmjyxsckq9-etc-pam-environment.drv' failed to build
error: 1 dependencies of derivation '/nix/store/z5lgypqfb8yi2xf4sknyjgkkkzi6v0kr-man-cache.drv' failed to build
error: 1 dependencies of derivation '/nix/store/4kdnw0lq6agqjkbmv577g80nx18gh987-set-environment.drv' failed to build
error: 1 dependencies of derivation '/nix/store/9b62fw5yq875d2ilvb7hjy9q5g6ydm6s-unit-accounts-daemon.service.drv' failed to build
error: 1 dependencies of derivation '/nix/store/d0y49fm0s1migr0ccmff94ikif4mqpch-X-Restart-Triggers-dbus.drv' failed to build
error: 1 dependencies of derivation '/nix/store/clijrdlji2y8y672da9n96jnqlzlh5ym-etc-man_db.conf.drv' failed to build
error: 1 dependencies of derivation '/nix/store/6c7nkxscwi59ydq8i4r3sz7y4d0w8d59-etc-profile.drv' failed to build
error: 1 dependencies of derivation '/nix/store/qyq637v81j9n2yvf3yypyffmcrima4jb-etc-zshenv.drv' failed to build
error: 1 dependencies of derivation '/nix/store/2wyxrkdklscmzk21x4klfn2z289mklq6-unit-polkit.service.drv' failed to build
error: 1 dependencies of derivation '/nix/store/gas3wlyzjd96lcz1gqz4hfdcljfggq2r-unit-dbus.service.drv' failed to build
error: 1 dependencies of derivation '/nix/store/kjk081lvhz6hwrjbn8jm87lsl1aqxdmb-unit-dbus.service.drv' failed to build
error: 3 dependencies of derivation '/nix/store/x1pzsi502467fn6wfvqdpbrv0vrq59z7-system-units.drv' failed to build
error: 1 dependencies of derivation '/nix/store/mryj6fqplbb2yrcr6krkph3ajq9phpyx-user-units.drv' failed to build
error: 9 dependencies of derivation '/nix/store/lk2d4dh23zrly4mdq7vwhpb48vs6wm75-etc.drv' failed to build

I know that I may have corrupted some nix store paths when I accidentally turned off my computer mid-upgrade. So I’ll look for corrupted paths and try to repair them: 

nix-store --verify-path $(nix-store -qR /nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv)

This returned nothing. Not sure if that’s good or bad.

Looking at journalctl I see: 

Dec 07 21:00:45 ░░░░░ audit[59815]: ANOM_ABEND auid=1000 uid=30001 gid=30000 ses=3 subj=kernel pid=59815 comm="meson" exe="/nix/store/qp5zys77biz7imbk6yy85q5pdv7qk84j-python3-3.11.6/bin/python3.11" sig=7 res=1
Dec 07 21:00:45 ░░░░░ kernel: audit: type=1701 audit(1702011645.866:175): auid=1000 uid=30001 gid=30000 ses=3 subj=kernel pid=59815 comm="meson" exe="/nix/store/qp5zys77biz7imbk6yy85q5pdv7qk84j-python3-3.11.6/bin/python3.11" sig=7 res=1
Dec 07 21:00:45 ░░░░░ audit: BPF prog-id=338 op=LOAD
Dec 07 21:00:45 ░░░░░ kernel: audit: type=1334 audit(1702011645.883:176): prog-id=338 op=LOAD
Dec 07 21:00:45 ░░░░░ audit: BPF prog-id=339 op=LOAD
Dec 07 21:00:45 ░░░░░ audit: BPF prog-id=334 op=UNLOAD

I’m going to try to build it while keeping the failed output: 

NIX_PATH=nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/░░░░░/configuration.nix:/nix/var/nix/profiles/per-user/root/channels nix build -vL --file "<nixpkgs/nixos>" system --keep-failed

Hmm… now that I think about it, why is it trying to build xwayland instead of fetch it from a cache? Did I override something a while back?

I’ll check to see why my system depends on it: 

nix why-depends --derivation /nix/store/░░░░░-nixos-system-░░░░░-23.11.1431.░░░░░.drv /nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv
/nix/store/░░░░░-nixos-system-░░░░░-23.11.1431.░░░░░.drv
└───/nix/store/b4dm5ika5kya4z9g2mh60986i33vz9ff-system-path.drv
    └───/nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv

Welp, that’s not really helpful. Maybe I’ll compare its derivation to the standard xwayland derivation, since they seem to be different.

Comparing a diff of

  • /nix/store/llklx9i8w71yib3x6338lq8ldhdnbqnl-xwayland-23.2.2.drv (normal version)
  • /nix/store/1724qmj8zhyxibg1xqmrcnnj45anyipb-xwayland-23.2.2.drv (my weird version)

I see there’s a difference in mesonFlags:

Normal version:

      "mesonFlags": "-Dxwayland_eglstream=true -Dxcsecurity=true -Ddefault_font_path= -Dxkb_bin_dir=/nix/store/jlzjj0yn56pzgs5cwd69a335gb213sds-xkbcomp-1.4.6/bin -Dxkb_dir=/nix/store/w4m1s9q2hlisl2bbhxmlwmci1m7nxzdr-xkeyboard-config-2.40/etc/X11/xkb -Dxkb_output_dir=/1rz4g4znpzjwh1xymhjpm42vipw92pr73vdgl6xs1hycac8kf2n9/share/X11/xkb/compiled -Dlibunwind=true",

My version:

      "mesonFlags": "-Dxwayland_eglstream=true -Dxcsecurity=true -Ddefault_font_path=/run/current-system/sw/share/X11/fonts -Dxkb_bin_dir=/nix/store/jlzjj0yn56pzgs5cwd69a335gb213sds-xkbcomp-1.4.6/bin -Dxkb_dir=/nix/store/w4m1s9q2hlisl2bbhxmlwmci1m7nxzdr-xkeyboard-config-2.40/etc/X11/xkb -Dxkb_output_dir=/1rz4g4znpzjwh1xymhjpm42vipw92pr73vdgl6xs1hycac8kf2n9/share/X11/xkb/compiled -Dlibunwind=true",

Why is mine depending on /run/current-system/sw/share/X11/fonts? The sandbox won’t have access to that.

Checking out a nix repl for <nixpkgs/nixos> I see that config.programs.xwayland.package is indeed different than pkgs.xwayland. It looks like config.programs.xwayland.defaultFontPath is getting set somewhere. Maybe this has to do with this warning I ignored earlier: 

trace: warning: The option `fonts.fonts' defined in `/░░░░░/configuration.nix' has been renamed to `fonts.packages'.

Looking at my settings, I see that I have the following: 

  fonts = {
     fontDir.enable = true;
     # enableFontDir = true;
     fonts = with pkgs; [

I comment that fontDir.enable = true; line out. Now I see that the package matches up with the default one.

And now it builds correctly! (Though I haven’t checked if it actually works ;P)