# Live ISO Build — Findings & Architecture Notes

## Overview

The live ISO boots directly into a Cinnamon desktop session as user `live` with no password prompt. It is designed for hardware testing on XPS 9700 and serves as the installer delivery vehicle.

Builder: `iso/build-live-iso.sh` (host) → Docker container running `iso/_inner-build-live.sh` → `void-mklive/mklive.sh`

---

## Boot + Session Startup

### Kernel Cmdline
```
live.user=live console=tty0 console=ttyS0,115200
```
The `live.user=live` parameter is consumed by the vmklive dracut hook (`adduser.sh`) which creates the user inside the initramfs and sets password `voidlinux`.

### runit Stage 2 Override
We override `/etc/runit/2` to run `/etc/runit/live-setup.sh` before handing off to `runsvdir`. The script:
1. Adds extra groups (`plugdev input network docker`) to the live user
2. Writes `/etc/sudoers.d/live` (full passwordless sudo)
3. Configures `/etc/nix/nix.conf` (daemon mode, `trusted-users = root live`)
4. Auto-detects GPU and writes `/etc/X11/xorg.conf.d/20-gpu.conf`

After live-setup.sh, stage 2 mirrors the real `runit-void` exactly:
```sh
runsvchdir "${runlevel}"
ln -sf /etc/runit/runsvdir/current /run/runit/runsvdir/current
exec runsvdir -P /run/runit/runsvdir/current
```

### Services (runsvdir/default symlinks in overlay)
Enabled at build time via symlinks in `build/live-includes/etc/runit/runsvdir/default/`:
- `dbus`
- `NetworkManager`
- `lightdm`
- `nix-daemon`

> **Note:** Do NOT use mklive.sh's `-S` flag for service enable — it is not supported by the version used. Services must be wired via runsvdir symlinks in the include overlay.

---

## LightDM Autologin

### Critical: `lightdm-session` does not exist on Void Linux
The Void `lightdm` 1.32 package does **not** ship the `lightdm-session` binary. The default LightDM behaviour of spawning `lightdm-session` causes the session to crash immediately (exit code 1 in ~20ms) with no error message.

**Fix:** Set `session-wrapper=/etc/lightdm/Xsession` in `lightdm.conf`. The `/etc/lightdm/Xsession` wrapper **is** provided by the Void lightdm package and correctly sources `/etc/profile` → `/etc/profile.d/`.

### `greeter-env=` and `session-env=` are not supported
These options are silently ignored in LightDM 1.32 on Void. To propagate environment variables to the session use `/etc/profile.d/` scripts instead.

### lightdm.conf autologin lines must be commented
The vmklive dracut hook `display-manager-autologin.sh` uses `sed` to uncomment lines. The autologin lines in `lightdm.conf` must be present but commented out — the hook finds them by regex and uncomments them at boot.

```ini
[Seat:*]
#autologin-user=
#autologin-user-timeout=0
#autologin-session=
#user-session=
session-wrapper=/etc/lightdm/Xsession
greeter-session=lightdm-gtk-greeter
```

The `/etc/lightdm/.session` file (content: `cinnamon`) is read by the hook to set the session name.

---

## GPU Auto-Detection

`live-setup.sh` runs `lspci` at boot and writes `/etc/X11/xorg.conf.d/20-gpu.conf`:

| Detected | Xorg Config | Extra |
|----------|-------------|-------|
| Virtual (virtio/VMware/QEMU/VirtualBox) | `modesetting`, `AccelMethod none` | `LIBGL_ALWAYS_SOFTWARE=1` in `/etc/profile.d/live-env.sh` |
| NVIDIA + proprietary driver (`nvidia_drv.so`) | PRIME offload: Intel `modesetting` + NVIDIA `nvidia` | No software GL |
| NVIDIA without proprietary driver | `modesetting` | — |
| Intel / AMD / other | `modesetting` | — |

`LIBGL_ALWAYS_SOFTWARE=1` is set via `/etc/profile.d/live-env.sh`, not via `session-env=` (unsupported).

---

## Nix Integration

### Daemon mode (not single-user)
The Void `nix` xbps package ships `nix-daemon` with a runit service at `/etc/sv/nix-daemon`. The daemon puts its socket at:
```
/var/nix/daemon-socket/socket
```

We use daemon mode (not single-user) because `/nix/store` stays root-owned. The live user is granted trust via `nix.conf`:
```
experimental-features = nix-command flakes
sandbox = false
auto-optimise-store = true
trusted-users = root live
```

`sandbox = false` is required because the live system has no `nixbld` users and no user namespaces in the dracut initramfs environment.

### Package list
`/usr/local/libexec/nix-packages.list` is written at ISO build time from `NIX_USER_PACKAGES` in `config/install.conf`. At first login, `first-login.sh` reads this file and runs `nix profile install --impure` with `NIXPKGS_ALLOW_UNFREE=1`.

Current packages:
- `nixpkgs#google-chrome`
- `nixpkgs#spotify`
- `nixpkgs#discord`
- `nixpkgs#localsend`
- `nixpkgs#mission-center`

### postinstall.sh socket path (installed system)
In the **installed system** (not live), `installer/lib/postinstall.sh` polls for the nix-daemon socket. The correct path is:
```
/var/nix/daemon-socket/socket
```
Not `/nix/var/nix/daemon-socket/socket` (upstream Nix default) — Void's package uses `/var/nix/`.

---

## dconf / Theme

The Gruvbox-Dark GTK theme and Cinnamon dconf settings are pre-applied via a system-db. The dconf binary database must be compiled at **ISO build time**, not at runtime.

### Build-time compilation
`iso/_inner-build-live.sh` runs inside the Debian Docker container. The Dockerfile installs `dconf-cli` for this step. The correct Debian `dconf-cli` API is:
```sh
dconf compile <output_binary_db> <input_keyfile_dir>
# e.g.:
dconf compile build/live-includes/etc/dconf/db/local \
              build/live-includes/etc/dconf/db/local.d
```

> **Note:** `dconf update <path>` does not work in Debian's `dconf-cli` — it only updates the user's own db. `dconf compile` is the correct tool for building a system-db binary.

### dconf profile
`/etc/dconf/profile/user` must point to the system-db:
```
user-db:user
system-db:local
```
Without this file, the compiled system-db is ignored and Cinnamon shows a black wallpaper with default GTK theme.

---

## First-Login Setup (`installer/first-login.sh`)

Runs once via XDG autostart (`~/.config/autostart/void-live-first-login.desktop`) when Cinnamon first loads. Installs:

1. **Claude Code** — official installer from `https://claude.ai/install.sh`
2. **Nix user packages** — from `/usr/local/libexec/nix-packages.list`
3. **NVM + Node LTS**
4. **VS Code extensions** — from `/etc/installer-vscode-extensions.txt`

Idempotent: creates `~/.first-login-done` on success. Logs to `~/.first-login.log`.

The script does NOT use `set -u` because `nvm.sh` references unbound variables.

---

## Build Pipeline

```
iso/build-live-iso.sh        (host — stages overlay, builds Docker image if needed)
  └─ Docker: void-installer-builder:latest
       └─ iso/_inner-build-live.sh
            ├─ dconf compile  (pre-bakes system-db)
            └─ void-mklive/mklive.sh -a x86_64 -r <repo> -I <include_dir> ...
                 └─ squashfs + GRUB + ISO 9660
```

Output: `out/void-live-stable.iso` (~2.9 GB)

### Build artifacts that must NOT be committed
- `build/live-includes/` — generated staging tree (hundreds of binary assets)
- `out/` — ISO output
- `cache/` — cloned void-mklive, xbps package cache

---

## Known Issues & Fixes

### `nix-env --switch-profile "$HOME/.nix-profile"` creates a circular symlink
**Symptom:** `error: filesystem error: status: Too many levels of symbolic links [/home/live/.nix-profile/manifest.json]` and `tar: xz: Cannot exec: Too many levels of symbolic links` (all binaries fail to exec via nix PATH).  
**Cause:** Passing `$HOME/.nix-profile` as the target to `nix-env --switch-profile` creates `~/.nix-profile -> .nix-profile` — a symlink that points to itself. This corrupts the nix profile directory and causes ELOOP on any file lookup under that path.  
**Fix:** Do not call `nix-env --switch-profile` at all when using `nix profile add` (new-style commands). Let `nix profile add` initialise the profile automatically. The first-login script also contains a guard that detects and removes the circular symlink before proceeding.

### `nix profile install` is deprecated
Use `nix profile add` instead. `nix profile install` is an alias that emits a warning and will be removed in a future Nix version.

### DNS hang in live environment (nsswitch `mdns` without Avahi)
**Symptom:** `getent hosts github.com` hangs indefinitely; `first-login.sh` stuck at "starting".  
**Cause:** `/etc/nsswitch.conf` includes `mdns` in the `hosts:` line. On Void Linux, `libnss_mdns.so.2` may not be present, and even if it is, the Avahi daemon is not running in the live session. glibc waits for Avahi's D-Bus socket before timing out.  
**Fix:** `live-setup.sh` runs at boot and removes `mdns` from `nsswitch.conf`: `sed -i '/^hosts:/s/mdns[^ ]* *//g' /etc/nsswitch.conf`. This is safe on real hardware (NetworkManager provides proper DNS via DHCP).

### QEMU internal DNS (10.0.2.3) unreliable
**Symptom:** Even after removing `mdns`, DNS queries to QEMU's built-in resolver (10.0.2.3) time out.  
**Cause:** QEMU's user-mode DNS proxy may not forward queries correctly depending on the host network configuration.  
**Workaround for QEMU testing:** `echo nameserver 8.8.8.8 > /etc/resolv.conf`. This is not needed on real hardware.

---

```bash
cp /usr/share/OVMF/OVMF_VARS.fd out/OVMF_VARS.live.fd
qemu-system-x86_64 -name void-live-test -machine q35,accel=kvm:tcg -cpu max \
  -m 4096 -smp 4 \
  -drive "if=pflash,format=raw,readonly=on,file=/usr/share/OVMF/OVMF_CODE.fd" \
  -drive "if=pflash,format=raw,file=out/OVMF_VARS.live.fd" \
  -cdrom out/void-live-stable.iso -boot order=d,menu=off \
  -netdev user,id=n0 -device virtio-net-pci,netdev=n0 \
  -serial "unix:out/live-serial.sock,server,nowait" \
  -monitor "unix:out/qemu-monitor.sock,server,nowait" \
  -device virtio-vga -display gtk,gl=off &
```

Serial console access (root shell for diagnostics):
```python
import socket, time
s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
s.connect('out/live-serial.sock')
# send commands, read output
```

GPU in QEMU: `virtio-vga` is detected as virtual → `modesetting + LIBGL_ALWAYS_SOFTWARE=1`.