Improve installer VM compatibility

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

iso/sovran-install-headless.sh

@@ -12,6 +12,11 @@ Options:
   --deploy-key "ssh-ed25519 AAAA..."  SSH pubkey for remote access after install
   --headscale-server URL       Headscale login server for post-install Tailnet
   --headscale-key KEY          Headscale pre-auth key for the installed OS
+
+VM notes:
+  Desktop test installs still need a 256 GB OS disk (thin-provisioned is OK).
+  Node/server installs need a separate 2 TB data disk. UEFI is preferred; UEFI
+  VMs avoid NVRAM boot-entry writes, and legacy BIOS VMs use GRUB.
 USAGE
 }
 
@@ -25,6 +30,8 @@ DEPLOY_KEY=""
 HEADSCALE_SERVER=""
 HEADSCALE_KEY=""
 DATA_DISK_HAS_TIMECHAIN=false
+BOOT_MODE=""
+VIRTUALIZATION=""
 
 FLAKE="/etc/sovran/flake"
 LOG="/tmp/sovran-headless-install.log"
@@ -69,6 +76,22 @@ case "$ROLE" in
     *) die "--role must be one of: server, desktop, node" ;;
 esac
 
+# ── Detect firmware / VM environment ─────────────────────────────────────────
+if [[ -d /sys/firmware/efi ]]; then
+    BOOT_MODE="uefi"
+else
+    BOOT_MODE="bios"
+fi
+
+if command -v systemd-detect-virt >/dev/null 2>&1; then
+    if VIRT_RESULT=$(systemd-detect-virt --vm 2>/dev/null); then
+        [[ "$VIRT_RESULT" != "none" ]] && VIRTUALIZATION="$VIRT_RESULT"
+    fi
+fi
+
+log "Boot mode: ${BOOT_MODE} ($([[ "$BOOT_MODE" == uefi ]] && echo systemd-boot || echo GRUB))"
+[[ -n "$VIRTUALIZATION" ]] && log "Virtual machine detected: ${VIRTUALIZATION}"
+
 # ── Validate disk existence and size ─────────────────────────────────────────
 log "=== Validating disks ==="
 
@@ -96,13 +119,26 @@ fi
 # ── Helper: partition suffix ──────────────────────────────────────────────────
 part_suffix() {
     local dev="$1" n="$2"
-    if [[ "$dev" == *nvme* ]]; then
+    local base
+    base=$(basename "$dev")
+    if [[ "$base" == nvme* || "$base" == mmcblk* || "$base" == loop* || "$base" == md* || "$base" =~ [0-9]$ ]]; then
         echo "${dev}p${n}"
     else
         echo "${dev}${n}"
     fi
 }
 
+nix_string() {
+    local value="$1"
+    value="${value//\\/\\\\}"
+    value="${value//\"/\\\"}"
+    value="${value//$'\n'/\\n}"
+    value="${value//$'\r'/\\r}"
+    value="${value//$'\t'/\\t}"
+    value="${value//\$\{/\\\$\{}"
+    printf '"%s"' "$value"
+}
+
 # ── Detect existing Bitcoin timechain data on data disk ───────────────────────
 if [[ -n "$DATA_DISK" ]]; then
     DATA_P1=$(part_suffix "$DATA_DISK" 1)
@@ -142,12 +178,19 @@ partprobe "$DISK"
 sleep 2
 
 # ── Step 2: Partition OS disk ─────────────────────────────────────────────────
-log "=== Partitioning OS disk ==="
-
-sgdisk \
-    -n "1:1M:+512M" -t "1:EF00" -c "1:ESP" \
-    -n "2:0:0"      -t "2:8300" -c "2:root" \
-    "$DISK"
+if [[ "$BOOT_MODE" == "uefi" ]]; then
+    log "=== Partitioning OS disk (UEFI) ==="
+    sgdisk \
+        -n "1:1M:+512M" -t "1:EF00" -c "1:ESP" \
+        -n "2:0:0"      -t "2:8300" -c "2:root" \
+        "$DISK"
+else
+    log "=== Partitioning OS disk (Legacy BIOS) ==="
+    sgdisk \
+        -n "1:1M:+1M" -t "1:EF02" -c "1:BIOS-boot" \
+        -n "2:0:0"    -t "2:8300" -c "2:root" \
+        "$DISK"
+fi
 
 partprobe "$DISK"
 sleep 2
@@ -168,7 +211,11 @@ log "=== Formatting partitions ==="
 BOOT_P1=$(part_suffix "$DISK" 1)
 BOOT_P2=$(part_suffix "$DISK" 2)
 
-mkfs.vfat -F 32 "$BOOT_P1"
+if [[ "$BOOT_MODE" == "uefi" ]]; then
+    mkfs.vfat -F 32 "$BOOT_P1"
+else
+    log "Skipping ESP format for Legacy BIOS install"
+fi
 mkfs.ext4 -F -L sovran_systemsos "$BOOT_P2"
 
 if [[ -n "$DATA_DISK" && "$DATA_DISK_HAS_TIMECHAIN" != true ]]; then
@@ -180,8 +227,12 @@ fi
 log "=== Mounting filesystems ==="
 
 mount "$BOOT_P2" /mnt
-mkdir -p /mnt/boot/efi
-mount -o umask=0077,defaults "$BOOT_P1" /mnt/boot/efi
+if [[ "$BOOT_MODE" == "uefi" ]]; then
+    mkdir -p /mnt/boot/efi
+    mount -o umask=0077,defaults "$BOOT_P1" /mnt/boot/efi
+else
+    log "Legacy BIOS install: /boot/efi mount not required"
+fi
 
 if [[ -n "$DATA_DISK" ]]; then
     DATA_P1=$(part_suffix "$DATA_DISK" 1)
@@ -219,16 +270,41 @@ case "$ROLE" in
         IS_SERVER=false; IS_DESKTOP=false; IS_NODE=true ;;
 esac
 
-cat > /mnt/etc/nixos/role-state.nix <<EOF
+{
+    cat <<EOF
 # THIS FILE IS AUTO-GENERATED BY THE INSTALLER. DO NOT EDIT.
 { config, lib, ... }:
 {
   sovran_systemsOS.roles.server_plus_desktop = lib.mkDefault ${IS_SERVER};
   sovran_systemsOS.roles.desktop = lib.mkDefault ${IS_DESKTOP};
   sovran_systemsOS.roles.node = lib.mkDefault ${IS_NODE};
-}
 EOF
 
+    if [[ "$BOOT_MODE" == "bios" ]]; then
+        GRUB_DEVICE=$(nix_string "$DISK")
+        cat <<EOF
+
+  # The installer ISO was booted in Legacy BIOS mode, so install GRUB to the
+  # target disk instead of using the default UEFI systemd-boot configuration.
+  boot.loader.systemd-boot.enable = lib.mkForce false;
+  boot.loader.efi.canTouchEfiVariables = lib.mkForce false;
+  boot.loader.grub.enable = lib.mkForce true;
+  boot.loader.grub.device = lib.mkForce ${GRUB_DEVICE};
+  fileSystems."/boot/efi".enable = lib.mkForce false;
+EOF
+    elif [[ -n "$VIRTUALIZATION" ]]; then
+        cat <<EOF
+
+  # VM UEFI firmware can reject or forget NVRAM boot-entry writes. Keep the
+  # normal UEFI systemd-boot layout, but use the fallback removable path instead
+  # of depending on EFI variable updates.
+  boot.loader.efi.canTouchEfiVariables = lib.mkForce false;
+EOF
+    fi
+
+    echo "}"
+} > /mnt/etc/nixos/role-state.nix
+
 # ── Step 10: Write custom.nix with deploy config ──────────────────────────────
 log "=== Writing custom.nix ==="