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|
# nixos-config - My current NixOS configuration
#
# Copyright (C) 2025 Jörg Thalheim and contributors
# SPDX-License-Identifier: MIT
#
# This file is part of my nixos-config.
#
# You should have received a copy of the License along with this program.
# If not, see <https://www.gnu.org/licenses/gpl-3.0.txt>.
# This file contains the code that is used to setup the VM shell.
{cfg}: {
lib,
config,
pkgs,
modulesPath,
...
}: let
mkVMDefault = lib.mkOverride 970;
env_file = "/tmp/shared/.env_variables";
in {
imports = [
(modulesPath + "/profiles/qemu-guest.nix")
(modulesPath + "/virtualisation/qemu-vm.nix")
];
config = {
assertions = [
{
assertion = builtins.elem cfg.user_name (lib.mapAttrsToList (name: value: name) config.users.users);
message = ''
Your user ${cfg.user_name} is not a recorded user in `config.users.users`.
Auto-login will not work.
'';
}
];
# Lock root login.
users.users.root.hashedPassword = "";
# Remove unneeded clutter.
system.switch.enable = false;
virtualisation = {
# See https://wiki.qemu.org/Documentation/9psetup#Performance_Considerations.
# It is effectively a balance between ram and IO speed.
msize = let
kib = x: x * 1024;
in
mkVMDefault (kib 512);
graphics = mkVMDefault false;
memorySize = mkVMDefault 1700; # in MB
cores = mkVMDefault 16;
# Do not persist this VM.
diskImage = mkVMDefault null;
fileSystems =
lib.mapAttrs'
(_: mount: {
name = mount.target;
value = {
device = mount.tag;
fsType = "9p";
options =
[
"trans=virtio"
"version=9p2000.L"
"cache=${mount.cache_mode}"
"msize=${toString config.virtualisation.msize}"
]
++ lib.optionals mount.readOnly ["ro"];
};
})
cfg.mounts;
qemu = {
consoles = lib.mkIf (!config.virtualisation.graphics) ["tty0" "hvc0"];
options = let
mkMount = options: "-virtfs " + (builtins.concatStringsSep "," options);
in
lib.optionals (!config.virtualisation.graphics) [
"-serial null"
"-device virtio-serial"
"-chardev stdio,mux=on,id=char0,signal=off"
"-mon chardev=char0,mode=readline"
"-device virtconsole,chardev=char0,nr=0"
]
++ (lib.mapAttrsToList
(hostPath: mount:
mkMount [
"local"
"path=${builtins.toString hostPath}"
"security_model=none"
"readonly=on"
"mount_tag=${mount.tag}"
])
cfg.mounts);
};
};
services = {
getty.helpLine = ''
If you are connect via serial console:
Type Ctrl-a c to switch to the qemu console
and `quit` to stop the VM.
'';
getty.autologinUser = cfg.user_name;
};
system.activationScripts = {
mountAdditionalPaths =
# bash
''
PATH="${pkgs.jq}/bin:${pkgs.util-linux}/bin:$PATH"
export PATH
max_index="$(jq '.mount | keys | length' --raw-output ${env_file})"
index=0
mount --mkdir --type=tmpfs none "/.rw" --options=rw,relatime,mode=0755
while [ "$index" -lt "$max_index" ]; do
what="$(jq --argjson index "$index" '.mount | keys | map(.)[$index]' --raw-output ${env_file})"
where="$(jq --argjson index "$index" '.mount | map(.)[$index]' --raw-output ${env_file})"
mkdir "/.rw/$what"
mount --mkdir "$what" "/.ro/$what" \
--type=9p \
--options=ro,trans=virtio,version=9p2000.L,msize=${toString config.virtualisation.msize},x-systemd.requires=modprobe@9pnet_virtio.service
mkdir "/.rw/work-$what"
mount --mkdir --type=overlay overlay \
--options=rw,relatime,lowerdir="/.ro/$what",upperdir="/.rw/$what",workdir="/.rw/work-$what",uuid=on \
"/.ov/$what"
index="$((index + 1))"
done
'';
};
systemd.services.mountAdditionalPaths = {
after = ["local-fs.target"];
wantedBy = ["multi-user.target"];
path = [pkgs.jq];
script =
# bash
''
max_index="$(jq '.mount | keys | length' --raw-output ${env_file})"
index=0
while [ "$index" -lt "$max_index" ]; do
what="$(jq --argjson index "$index" '.mount | keys | map(.)[$index]' --raw-output ${env_file})"
where="$(jq --argjson index "$index" '.mount | map(.)[$index]' --raw-output ${env_file})"
systemd-mount --type none "/.ov/$what" "$where" --options=bind
# HACK(@bpeetz): Nearly all of the paths are in $HOME anyways. So simply avoid
# the permission issue.
# Ideally, we would pass the original owners along with the mount. <2025-05-17>
chown --recursive soispha:users "/home/soispha"
index="$((index + 1))"
done
'';
};
environment = {
systemPackages = [
pkgs.jq
];
sessionVariables = {
IN_NIXOS_SHELL = "true";
};
loginShellInit =
# bash
''
cd "$(jq '.pwd' --raw-output ${env_file})"
export TERM="$(jq '.term' --raw-output ${env_file})"
export PATH="$(jq '.path' --raw-output ${env_file}):$PATH"
'';
};
networking.firewall.enable = mkVMDefault true;
};
}
|
