fist commit - images lib in a working condition for debian

lib/images/commons/customizeImage.nix

@@ -0,0 +1,49 @@
+# wrapper function around virt-customize to create custom OS image from an original OS image
+{ pkgs, lib, ... }:
+  originalImage: {
+    name,
+    hostname ? "",
+    nameToHostname ? true,
+    diskSize ? "",
+    smp ? 2,
+    memSize ? 1024,
+    install ? [],
+    run ? "",
+    commands ? "",
+    osType ? "linux"
+  }:
+  let
+    originalImageName = lib.strings.removeSuffix "-vmix" (lib.strings.removeSuffix ".qcow2" originalImage.name);
+    resultImg = "./disk.qcow2";
+    qemuWrapperScript = (pkgs.writeShellScript "qemu-wrapper-script" ''
+      export PATH="${pkgs.qemu}/bin:$PATH"
+      exec qemu-kvm -nic user,model=virtio-net-pci "$@"
+    '');
+    setHostname = if hostname != "" then hostname else if nameToHostname then name else "";
+    virtCustomizeArgsHostname = if setHostname != "" then "--hostname '${setHostname}'" else "";
+    virtCustomizeArgsInstall = if install != [] then "--install '${lib.strings.concatStringsSep "," install }'" else "";
+    virtCustomizeArgsCommandsFile = if commands != "" then  ("--commands-from-file " + pkgs.writeText "${name}-vmix-virt-customize-commands-file" commands) else "";
+    virtCustomizeArgsRun = if run != "" then ("--run " + pkgs.writeScript "${name}-vmix-virt-customize-run-script" "${run}") else "";
+  in
+  pkgs.runCommand "${name}-${originalImageName}-vmix.qcow2" { __noChroot = true; } ''
+    export PATH="${pkgs.qemu}/bin:${pkgs.curl}/bin:$PATH"
+
+    # create resulting image backed by original image
+    qemu-img create -f qcow2 -b ${originalImage} -F qcow2 ${resultImg}
+    [ -n "${diskSize}" ] && qemu-img resize ${resultImg} ${diskSize}
+
+    # run script inside image using virt-customize
+    export LIBGUESTFS_APPEND="ipv6.disable=1"
+    #export LIBGUESTFS_HV="${qemuWrapperScript}"
+
+    ${pkgs.guestfs-tools}/bin/virt-customize \
+      -a ${resultImg} \
+      --smp ${builtins.toString smp} \
+      --memsize ${builtins.toString memSize} \
+      ${virtCustomizeArgsHostname} \
+      ${virtCustomizeArgsInstall} \
+      ${virtCustomizeArgsCommandsFile} \
+      ${virtCustomizeArgsRun}
+
+    mv ${resultImg} $out
+  ''

lib/images/commons/default.nix

@@ -0,0 +1,5 @@
+{ pkgs, lib, ... }: {
+  # basic scripts and files used across various OS images
+  customizeImage = (import ./customizeImage.nix) { inherit pkgs lib; };
+  scriptsNFiles = (import ./scripts-n-files.nix) { inherit pkgs lib; };
+}

lib/images/commons/scripts-n-files.nix

@@ -0,0 +1,59 @@
+# minimal set of scripts and services by various images
+{ pkgs, lib, ... }: {
+  # bring back simple interface names like eth0 eth1 etc
+  grub-ifnames-0 = pkgs.writeText "grub-ifnames-0" ''
+    GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0 $GRUB_CMDLINE_LINUX"
+  '';
+
+  # no need for CPU microcode updating in VMs
+  grub-disable-microcode = pkgs.writeText "grub-disable-microcode" ''
+    GRUB_CMDLINE_LINUX="dis_ucode_ldr $GRUB_CMDLINE_LINUX"
+  '';
+
+  # dhcp for eth0
+  eth0-dhcp-network = pkgs.writeText "eth0-network" ''
+    [Match]
+    Name=eth0
+
+    [Network]
+    DHCP=yes
+  '';
+
+  # generate ssh host keys before starting sshd
+  ssh-service-override-conf-create = pkgs.writeScript "ssh-override-conf-create.sh" ''
+    mkdir -p /etc/systemd/system/ssh.service.d
+
+    cat > /etc/systemd/system/ssh.service.d/override.conf << EOF
+    [Service]
+    ExecStartPre=
+    ExecStartPre=`which ssh-keygen` -A
+    ExecStartPre=`which sshd` -t
+
+    EOF
+  '';
+
+  # script to grow root partition
+  grow-root-sh = pkgs.writeScript "grow-root-sh" ''
+    #!/bin/bash
+    set -e
+
+    command -v growpart >/dev/null || { >&2 echo "growpart not found. Install package cloud-guest-utils or cloud-utils."; exit 1; }
+
+    ROOTPART=$(findmnt / -o source -n)
+    DISK=''${ROOTPART%[0-9]*}
+    PARTNUM=''${ROOTPART##*[!0-9]}
+
+    # resize and grow if possible
+    growpart "$DISK" "$PARTNUM" && resize2fs "$ROOTPART" || true
+  '';
+
+  # service to grow root partition on boot
+  grow-root-service = pkgs.writeText "grow-root-service" ''
+    [Service]
+    Type = oneshot
+    ExecStart = /usr/local/sbin/grow-root.sh
+
+    [Install]
+    WantedBy = multi-user.target
+  '';
+}