NixOS notes

Installation

Installed from the current iso:

nixos-gnome-23.11.5541.56528ee42526-x86_64-linux.iso

This does not enforce gnome. We can choose the desktop environment during the install. The installer includes partitioning. The alternative isos seem more limited.

A newer version will be available in May 2024 and it should be possible to switch to it via the setting system.autoUpgrade.channel or a suitable nix-channel --add command.

TODO: document this when done.

Problem with unstable

Changing to unstable to get plasma6 caused problems and failed rebuilds.

Rebuilding

nixos-rebuild switch

Removing old generations

In /nix/var/nix/profiles/ remove the unwanted symlinks, then run

nix --extra-experimental-features nix-command store gc

Then it may also be necessary to remove the corresponding boot loader entries in /boot/loader/entries.

Re-installing or installing on a different machine

The old /etc/nixos/configuration.nix can be dropped in to the new installation but we need to import the new hardware-configuration.nix.

Note that hardware-configuration.nix contains the partition layout.

Wireless

The relevant modules are blacklisted at the moment.

# cat /etc/nixos/networking/wireless-off.nix
{ config, pkgs, ... }:
{
    boot.blacklistedKernelModules = [
         "iwlwifi"
         "iwlmvm"
    ];
}

Autofs

# cat /etc/nixos/networking/autofs.nix
{ config, pkgs, ... }:
{
    services.autofs.enable = true;
    services.autofs.autoMaster = let
    mapConf = pkgs.writeText "auto" ''
    isos    -fstype=nfs4,ro          teapot:/isos
    rmt     -fstype=nfs4,ro          rmt:/repo
    smt     -fstype=nfs4,ro          teapot:/repo
    ins     -fstype=nfs,ro,nolock    tigerlily:/ins
    tisos   -fstype=nfs,ro,nolock    tigerlily:/isos
'';
    in ''/autofs file:${mapConf}'';
}

Problems

Getting openvpn to work

Using environment.etc to drop in

NetworkManager/system-connections/InfraVPN_Access_Corp_CZ.nmconnection

and then using nmcli failed for unclear reasons (apparently related to the bridged interface) with a message:

Error: Connection activation failed: Could not find source connection.

So we now have /etc/openvpn/openvpn.conf and dnsmasq for split DNS and scripts in /root/bin to start and stop the connection while replacing /etc/dnsmasq-conf.conf as needed.

Printing

Initially command line printing of pdf files did not work.

This was fixed by using

services.printing.drivers = [ pkgs.hplip ];

instead of

services.printing.drivers = [ pkgs.gutenprint ];

Fonts

It seems we need to deal with these separately from system packages:

fonts.packages = with pkgs; [
  corefonts
  fantasque-sans-mono
  google-fonts
  libertine
  monaspace
  nika-fonts
  noto-fonts
  open-sans
  stix-two
  stix-otf
];

Cron

Using crontab -e as root sets up a cron job that seems to work, but this is not the NixOS way. Using services.cron.systemCronJobs seems to fail, and there are complaints online about this. See below.

Mplayer

After just installing Mplayer, we see

No such driver: v4l2

This comment shows how to fix it:

https://www.reddit.com/r/NixOS/comments/xx5za7/no_such_driver_v4l2/

We need:

nixpkgs.config = {
 packageOverrides = super: {
      mplayer = super.mplayer.override {
        v4lSupport = true;
      };
 };
};

Systemd timers instead of cron

This works fine. Note that we need to source /etc/profile in the script section to make it work, otherwise the commands are not in the path.

[root@star:/etc/nixos]# cat run-config-backup.nix
{ config, pkgs, ... }:
{
    systemd.timers."run-config-backup" = {
         wantedBy = [ "timers.target" ];
         timerConfig = {
           OnCalendar="*-*-* 10:30:00";
           Persistent = true;
           Unit = "run-config-backup.service";
         };
    };
    systemd.services."run-config-backup" = {
         script = ''
source /etc/profile
DATE=$(date +%Y%m%d-%H%M)
fdisk -l > /tmp/fdisk-l
mount > /tmp/mount
ssh root@tigerlily mkdir -p /install/backup/star/$DATE
ssh root@tigerlily mkdir -p /install/backup/star/$DATE/etc
rsync -avvL /etc/nixos root@tigerlily:/install/backup/star/$DATE/etc
rsync -avv /root root@tigerlily:/install/backup/star/$DATE/
rsync -avv /tmp/fdisk-l /tmp/mount root@tigerlily:/install/backup/star/$DATE/
'';
         serviceConfig = {
           Type = "oneshot";
           User = "root";
         };
    };
}

User owned example:

[root@star:/etc/nixos]# cat run-upload-nixos-notes.nix
{ config, pkgs, ... }:
{
    systemd.timers."run-upload-nixos-notes" = {
         wantedBy = [ "timers.target" ];
         timerConfig = {
           OnCalendar="*-*-* 13:20:00";
           Persistent = true;
           Unit = "run-upload-nixos-notes.service";
         };
    };
    systemd.services."run-upload-nixos-notes" = {
         script = ''
source /etc/profile
rsync -a -e 'ssh -p 2122' /home/roger/nixos-notes/out/lwarp.css \
/home/roger/nixos-notes/out/index.html \
/home/roger/nixos-notes/out/notes.html \
roger@disruptive.org.uk:/home/roger/WEB/doc/nixos-notes/
'';
         serviceConfig = {
           Type = "oneshot";
           User = "roger";
         };
    };
}

Desktop

desktop.nix is a symlink to plasma5.nix and can be swapped out for xfce.nix or another desktop setup.

Python

See: https://wiki.nixos.org/wiki/Python – section “Using the Nixpkgs Python infrastructure”.

Example: put the following into a file named shell.nix in a directory and then run nix-shell.

let
    pkgs = import  {};
in pkgs.mkShell {
    packages = [
         (pkgs.python3.withPackages (python-pkgs: [
          python-pkgs.pexpect
         ]))
    ];
}

The prompt will change to:

[nix-shell:~/test]$

and the python environment will be available.