Development machines made easy

I want to re-use a disk for /home (or at least $HOME/src) so that I can just re-attach it later on. We are assuming we have a base image working here, see virt-builder.

virsh --connect=qemu+tcp://wakasu.home:16509/system list

• zsh
• bash
• exa
• htop
• ssh/shhd

• nested virt => @virtualization, libvirt-devel

• podman-docker
• buildah
• skopeo
• ko
• kubectl
• google-cloud-sdk

The initial source of packer recipes comes from nix-community/nixbox, but I’m tailoring them to my needs

{
  "builders": [
    {
      "boot_wait": "40s",
      "boot_command": [
        "echo http://{{ .HTTPIP }}:{{ .HTTPPort}} > .packer_http<enter>",
        "mkdir -m 0700 .ssh<enter>",
        "curl $(cat .packer_http)/install_rsa.pub > .ssh/authorized_keys<enter>",
        "systemctl start sshd<enter>"
      ],
      "http_directory": "scripts",
      "iso_checksum_type": "sha256",
      "shutdown_command": "shutdown -h now",
      "ssh_private_key_file": "./scripts/install_rsa",
      "ssh_port": 22,
      "ssh_username": "root",
      "type": "qemu",
      "iso_url": "https://d3g5gsiof5omrk.cloudfront.net/nixos/18.09/nixos-18.09.1799.b9fa31cea0e/nixos-minimal-18.09.1799.b9fa31cea0e-x86_64-linux.iso",
      "iso_checksum": "cc7c399c5fe4672383fe54cb1d648854a0d6732765fe1a61bb38b3fe3b7c6d2f",
      "disk_interface": "virtio-scsi",
      "qemuargs": [
        [
          "-m",
          "1024"
        ]
      ]
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "script": "./scripts/install.sh"
    }
  ]
}

Let’s look at the provisioning script. We don’t want to create a full specific configuration for these images as we will use ansible for the final provisioning.

• scripts/install.sh

  #!/bin/sh -e
  
  packer_http=$(cat .packer_http)
  
  # Partition disk
  cat <<FDISK | fdisk /dev/sda
  n
  
  
  
  
  a
  w
  
  FDISK
  
  # Create filesystem
  mkfs.ext4 -j -L nixos /dev/sda1
  
  # Mount filesystem
  mount LABEL=nixos /mnt
  
  # Setup system
  nixos-generate-config --root /mnt
  
  curl -sf "$packer_http/machine.nix" > /mnt/etc/nixos/machine.nix
  curl -sf "$packer_http/builders/$PACKER_BUILDER_TYPE.nix" > /mnt/etc/nixos/hardware-builder.nix
  curl -sf "$packer_http/configuration.nix" > /mnt/etc/nixos/configuration.nix
  curl -sf "$packer_http/custom-configuration.nix" > /mnt/etc/nixos/custom-configuration.nix
  
  ### Install ###
  nixos-install
  
  ### Cleanup ###
  curl "$packer_http/postinstall.sh" | nixos-install
  

• scripts/postinstall.sh

  #!/bin/sh
  
  # Make sure we are totally up to date
  nix-channel --add https://nixos.org/channels/nixos-18.09 nixos
  nix-channel --update
  nixos-rebuild switch --upgrade
  
  # Cleanup any previous generations and delete old packages that can be
  # pruned.
  
  for x in $(seq 0 2) ; do
    nix-env --delete-generations old
    nix-collect-garbage -d
  done
  
  
  # Remove install ssh key
  rm -rf /root/.ssh /root/.packer_http
  
  # Zero out the disk (for better compression)
  dd if=/dev/zero of=/EMPTY bs=1M
  rm -rf /EMPTY
  

• scripts/machine.nix

  # This file is overwritten by the vagrant-nixos plugin
  { config, pkgs, ... }:
  {
    networking.hostName = "nixos-machine";
  }
  

• scripts/configuration.nix

  { config, pkgs, ... }:
  
  {
    imports =
      [ # Include the results of the hardware scan.
        ./hardware-configuration.nix
        ./hardware-builder.nix
        ./machine.nix
        ./custom-configuration.nix
      ];
  
    # Use the GRUB 2 boot loader.
    boot.loader.grub.enable = true;
    boot.loader.grub.version = 2;
    boot.loader.grub.device = "/dev/sda";
  
    # remove the fsck that runs at startup. It will always fail to run, stopping
    # your boot until you press *.
    boot.initrd.checkJournalingFS = false;
  
    # Services to enable:
  
    # Enable the OpenSSH daemon.
    services.openssh.enable = true;
  
    # Enable DBus
    services.dbus.enable    = true;
  
    # Replace nptd by timesyncd
    services.timesyncd.enable = true;
  
    # Packages for Vagrant
    environment.systemPackages = with pkgs; [
      iputils
    ];
  
    # Creates a "vincent" users with password-less sudo access
    users = {
      extraGroups = [ { name = "vincent"; } ];
      extraUsers  = [
        # Try to avoid ask password
        { name = "root"; password = "vincent"; }
        {
          description     = "Vincent User";
          name            = "vincent";
          group           = "vincent";
          extraGroups     = [ "users" "wheel" ];
          password        = "vincent";
          home            = "/home/vincent";
          createHome      = true;
          useDefaultShell = true;
          openssh.authorizedKeys.keys = [
            "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDO1sx5h44xnK/k0ODnQ3aQR8+nr7HC7u94fS3OhwQ6AvjqDGLnI6EP4sr4Yh2eXf8lHX+lkg8iZ6Z+y9dVnnzwveZfqbfOyh6t8Hg+M1nl26rwdYv+guU8khvh+Kzl9Vdb5dexf/hWQ/LcWvsuPO+tBmqajNTLYbGinqrMm3Bw2jJS/+DitgoT8hiuSTU1smY1CGzggHEdsx4+oDMuDMvRYwOBBHrUF00lZLx3zB3nGl1VFYD2St3vzlmzoZNrW7Rx8TRg02BTVAwd4qPHOMz8Kg+JmDhVig9yeqHo4FCwXxQ8+jk54Cd2el6TjfaA5HD2+e4FYLP6bMSLIabLTfLP vincent@wakasu"
          ];
        }
      ];
    };
  
    security.sudo.configFile =
      ''
        Defaults:root,%wheel env_keep+=LOCALE_ARCHIVE
        Defaults:root,%wheel env_keep+=NIX_PATH
        Defaults:root,%wheel env_keep+=TERMINFO_DIRS
        Defaults env_keep+=SSH_AUTH_SOCK
        Defaults lecture = never
        root   ALL=(ALL) SETENV: ALL
        %wheel ALL=(ALL) NOPASSWD: ALL, SETENV: ALL
      '';
  
  }
  

• scripts/custom-configuration.nix

  { config, pkgs, ... }:
  
  {
  # Place here any custom configuration specific to your organisation (locale, ...)
  # if you want it to be part of the packer base image to be used with vagrant.
  }
  

• scripts/builders/qemu.nix

  { modulesPath, ... }:
  {
    imports = [
      "${toString modulesPath}/profiles/qemu-guest.nix"
    ];
  }
  

And to build this image, a simple packer build nixos.json is required.