Streamline VM overlays and rootfs packages

Move the default guest package list into a repo manifest and record a hash beside built rootfs images so run/make-rootfs can warn when the docker-ready image is stale.

Switch the Firecracker launch path to a single sparse root overlay per VM instead of separate /home and /var disks, so many VMs can share the same base image while still installing packages under /var and working from /root.

Keep older images bootable by masking stale home.mount and var.mount units at boot, and scrub those obsolete fstab entries when customize.sh rebuilds an image. Verified with bash -n on the updated scripts; no live VM boot was run in this environment.

README.md

@@ -15,6 +15,7 @@ Minimal Firecracker launcher.
 - `wtf/root/lib/modules/6.8.0-94-generic/`: guest kernel modules
 - `rootfs.ext4`: guest root filesystem (base image if present)
 - `rootfs-docker.ext4`: docker-ready guest rootfs (built via `make-rootfs.sh`)
+- `packages.apt`: apt packages baked into rebuilt guest images
 - `id_ed25519`: SSH key for `root`
 - `mapdns`: local DNS mapping CLI used to publish `<vm-name>.vm` → guest IP records
 
@@ -25,22 +26,21 @@ Minimal Firecracker launcher.
 
 ## Run Options
 ```
-./run.sh --name calm_otter --vcpu 4 --ram 2048 --home-size 6G
+./run.sh --name calm-otter --vcpu 4 --ram 2048 --overlay-size 12G
 ```
 - `--name`: must be unique and match `[a-z0-9][a-z0-9-]{0,63}`.
 - `--vcpu`: defaults to 2, max 16.
 - `--ram`: MiB, defaults to 1024, max 32768.
+- `--overlay-size`: writable dm-snapshot size for VM changes under `/`, including `/root` and `/var` (default: 8G).
 - `--rootfs`: path to the rootfs image (default: `./rootfs-docker.ext4`).
 - `--kernel`: path to the kernel image (default: `./wtf/root/boot/vmlinux-6.8.0-94-generic`).
 - `--initrd`: path to the initrd image (default: `./wtf/root/boot/initrd.img-6.8.0-94-generic`).
-- `--home-size`: M/G suffixes supported (default: 2G).
-- `--var-size`: M/G suffixes supported (default: 2G).
 
 ## Storage Layout
 - `rootfs.ext4` is used as the read-only origin for a per-VM device-mapper snapshot mounted as `/`.
-- Each VM gets writable ext4 disks mounted at `/home` and `/var`.
+- Each VM gets one sparse writable overlay file (`cow.ext4`) that stores its changes on top of the shared base image.
-- `run.sh` seeds those `/home` and `/var` disks from the rootfs snapshot before boot so the guest sees the base image contents there on first boot.
+- `/root` and `/var` live inside that per-VM overlay, so VMs can install packages without copying separate disks per VM.
-- The base image must include `/etc/fstab` entries for `/dev/vdb` → `/home` and `/dev/vdc` → `/var`.
+- `run.sh` masks stale `home.mount` and `var.mount` units at boot so older images with `/dev/vdb` and `/dev/vdc` entries in `/etc/fstab` still boot.
 - `/run` and `/tmp` should be tmpfs via `/etc/fstab`.
 
 ## SSH
@@ -84,6 +84,9 @@ preloaded so Docker works out of the box. Pass the base rootfs as a positional
 argument; the output defaults to `docker-<base filename>` in the same directory
 unless you pass `--out`.
 
+Base guest packages come from `./packages.apt`. Edit that file to bake tools
+like `vim` and `tmux` into rebuilt images.
+
 ```
 ./customize.sh ./rootfs.ext4 --size 6G --docker
 ```
@@ -114,6 +117,16 @@ invoke `make-rootfs.sh` to build it.
 `make-rootfs.sh` chooses the first available base image:
 - `./rootfs.ext4`
 
+If `./packages.apt` changes after `rootfs-docker.ext4` is built, `run.sh` will
+warn and keep using the existing image. `make-rootfs.sh` will also warn and
+exit without rebuilding while the image already exists.
+
+To rebuild after package changes:
+```
+rm -f ./rootfs-docker.ext4 ./rootfs-docker.ext4.packages.sha256
+./make-rootfs.sh
+```
+
 ## Interactive Customization
 To create a writable copy and customize it manually over SSH (no automatic
 package/config changes), use:

customize.sh

@@ -31,6 +31,7 @@ parse_size() {
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 source "$DIR/dns.sh"
+source "$DIR/packages.sh"
 STATE="$DIR/state"
 VM_ROOT="$STATE/vms"
 mkdir -p "$VM_ROOT"
@@ -52,6 +53,7 @@ OUT_ROOTFS=""
 SIZE_SPEC=""
 INSTALL_DOCKER=0
 MODULES_DIR="$DIR/wtf/root/lib/modules/6.8.0-94-generic"
+PACKAGES_FILE="$(banger_packages_file)"
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --out)
@@ -136,6 +138,25 @@ if ! command -v jq >/dev/null 2>&1; then
   log "jq required"
   exit 1
 fi
+if ! command -v sha256sum >/dev/null 2>&1; then
+  log "sha256sum required to record package manifest metadata"
+  exit 1
+fi
+if [[ ! -f "$PACKAGES_FILE" ]]; then
+  log "package manifest not found: $PACKAGES_FILE"
+  exit 1
+fi
+
+APT_PACKAGES=()
+if ! banger_packages_read_array APT_PACKAGES "$PACKAGES_FILE"; then
+  log "package manifest is empty: $PACKAGES_FILE"
+  exit 1
+fi
+if ! PACKAGES_HASH="$(printf '%s\n' "${APT_PACKAGES[@]}" | banger_packages_hash_stream)"; then
+  log "failed to hash package manifest: $PACKAGES_FILE"
+  exit 1
+fi
+printf -v APT_PACKAGES_ESCAPED '%q ' "${APT_PACKAGES[@]}"
 
 log "copying base rootfs to $OUT_ROOTFS"
 cp --reflink=auto "$BASE_ROOTFS" "$OUT_ROOTFS"
@@ -223,7 +244,7 @@ sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/machine-config \
     "smt": false
   }' >/dev/null
 
-KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0:${VM_NAME}:eth0:off:${DNS_SERVER} hostname=${VM_NAME}"
+KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0:${VM_NAME}:eth0:off:${DNS_SERVER} hostname=${VM_NAME} systemd.mask=home.mount systemd.mask=var.mount"
 
 INITRD_JSON=""
 if [[ -n "$INITRD" ]]; then
@@ -286,13 +307,19 @@ log "enabling NAT for customization"
 sudo -E ./nat.sh up "$VM_TAG" >/dev/null
 
 log "waiting for SSH"
+SSH_READY=0
 for _ in $(seq 1 60); do
   if ssh -i "$SSH_KEY" -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
     "root@${GUEST_IP}" "true" >/dev/null 2>&1; then
+    SSH_READY=1
     break
   fi
   sleep 1
 done
+if [[ "$SSH_READY" -ne 1 ]]; then
+  log "ssh did not become ready on $GUEST_IP"
+  exit 1
+fi
 
 log "configuring guest"
 ssh -i "$SSH_KEY" -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
@@ -300,13 +327,8 @@ ssh -i "$SSH_KEY" -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
 printf 'nameserver %s\n' \"$DNS_SERVER\" > /etc/resolv.conf
 echo \"$VM_NAME\" > /etc/hostname
 printf '127.0.0.1 localhost\n127.0.1.1 %s\n' \"$VM_NAME\" > /etc/hosts
-mkdir -p /home /var
+touch /etc/fstab
-if ! grep -q '^/dev/vdb ' /etc/fstab; then
+sed -i '\|^/dev/vdb[[:space:]]\+/home[[:space:]]|d; \|^/dev/vdc[[:space:]]\+/var[[:space:]]|d' /etc/fstab
-  echo '/dev/vdb /home ext4 defaults 0 2' >> /etc/fstab
-fi
-if ! grep -q '^/dev/vdc ' /etc/fstab; then
-  echo '/dev/vdc /var ext4 defaults 0 2' >> /etc/fstab
-fi
 if ! grep -q '^tmpfs /run ' /etc/fstab; then
   echo 'tmpfs /run tmpfs defaults,nodev,nosuid,mode=0755 0 0' >> /etc/fstab
 fi
@@ -315,7 +337,7 @@ if ! grep -q '^tmpfs /tmp ' /etc/fstab; then
 fi
 apt-get update
 DEBIAN_FRONTEND=noninteractive apt-get -y upgrade
-DEBIAN_FRONTEND=noninteractive apt-get -y install git less tree ca-certificates curl
+DEBIAN_FRONTEND=noninteractive apt-get -y install ${APT_PACKAGES_ESCAPED}
 if [[ \"$INSTALL_DOCKER\" == \"1\" ]]; then
   DEBIAN_FRONTEND=noninteractive apt-get -y remove containerd || true
   if ! DEBIAN_FRONTEND=noninteractive apt-get -y install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin; then
@@ -362,4 +384,5 @@ for _ in $(seq 1 200); do
   fi
   sleep 0.05
 done
+banger_write_rootfs_manifest_metadata "$OUT_ROOTFS" "$PACKAGES_HASH"
 log "done"

interactive.sh

@@ -7,7 +7,7 @@ log() {
 
 usage() {
   cat <<'EOF'
-Usage: ./interactive.sh <base-rootfs> [--out <path>] [--size <size>] [--home-size <size>] [--var-size <size>]
+Usage: ./interactive.sh <base-rootfs> [--out <path>] [--size <size>]
 
 Creates a writable copy of the base rootfs and boots a VM so you can
 customize it manually over SSH. No automatic package/config changes
@@ -45,14 +45,10 @@ BR_DEV="br-fc"
 BR_IP="172.16.0.1"
 CIDR="24"
 DNS_SERVER="1.1.1.1"
-DEFAULT_HOME_SIZE="2G"
-DEFAULT_VAR_SIZE="2G"
 
 BASE_ROOTFS=""
 OUT_ROOTFS=""
 SIZE_SPEC=""
-HOME_SIZE="$DEFAULT_HOME_SIZE"
-VAR_SIZE="$DEFAULT_VAR_SIZE"
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --out)
@@ -63,14 +59,6 @@ while [[ $# -gt 0 ]]; do
       SIZE_SPEC="${2:-}"
       shift 2
       ;;
-    --home-size)
-      HOME_SIZE="${2:-}"
-      shift 2
-      ;;
-    --var-size)
-      VAR_SIZE="${2:-}"
-      shift 2
-      ;;
     -h|--help)
       usage
       exit 0
@@ -115,9 +103,6 @@ if [[ -e "$OUT_ROOTFS" ]]; then
   exit 1
 fi
 
-HOME_BYTES="$(parse_size "$HOME_SIZE")" || { log "invalid --home-size value: $HOME_SIZE"; exit 1; }
-VAR_BYTES="$(parse_size "$VAR_SIZE")" || { log "invalid --var-size value: $VAR_SIZE"; exit 1; }
-
 log "copying base rootfs to $OUT_ROOTFS"
 cp --reflink=auto "$BASE_ROOTFS" "$OUT_ROOTFS"
 
@@ -143,8 +128,6 @@ mkdir -p "$VM_DIR"
 API_SOCK="${XDG_RUNTIME_DIR:-/run/user/$(id -u)}/banger/fc-$VM_TAG.sock"
 LOG_FILE="$VM_DIR/firecracker.log"
 TAP_DEV="tap-fc-$VM_TAG"
-HOME_PATH="$VM_DIR/home.ext4"
-VAR_PATH="$VM_DIR/var.ext4"
 DNS_NAME=""
 
 # Allocate guest IP
@@ -185,15 +168,6 @@ sudo ip link set "$TAP_DEV" master "$BR_DEV"
 sudo ip link set "$TAP_DEV" up
 sudo ip link set "$BR_DEV" up
 
-if ! command -v mkfs.ext4 >/dev/null 2>&1; then
-  log "mkfs.ext4 required to create home/var disks"
-  exit 1
-fi
-truncate -s "$HOME_BYTES" "$HOME_PATH"
-mkfs.ext4 -F "$HOME_PATH" >/dev/null
-truncate -s "$VAR_BYTES" "$VAR_PATH"
-mkfs.ext4 -F "$VAR_PATH" >/dev/null
-
 log "starting firecracker process"
 rm -f "$API_SOCK"
 nohup sudo -E "$FC_BIN" --api-sock "$API_SOCK" >"$LOG_FILE" 2>&1 &
@@ -215,7 +189,7 @@ sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/machine-config \
     "smt": false
   }' >/dev/null
 
-KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0:${VM_NAME}:eth0:off:${DNS_SERVER} hostname=${VM_NAME}"
+KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0:${VM_NAME}:eth0:off:${DNS_SERVER} hostname=${VM_NAME} systemd.mask=home.mount systemd.mask=var.mount"
 
 sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/boot-source \
   -H "Content-Type: application/json" \
@@ -234,24 +208,6 @@ sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/drives/rootfs \
     \"is_read_only\": false
   }" >/dev/null
 
-sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/drives/home \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"home\",
-    \"path_on_host\": \"$HOME_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
-sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/drives/var \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"var\",
-    \"path_on_host\": \"$VAR_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
 sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/network-interfaces/eth0 \
   -H "Content-Type: application/json" \
   -d "{

make-rootfs.sh

@@ -18,6 +18,7 @@ EOF
 }
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$DIR/packages.sh"
 OUT_ROOTFS="$DIR/rootfs-docker.ext4"
 SIZE_SPEC="6G"
 BASE_ROOTFS=""
@@ -45,6 +46,10 @@ while [[ $# -gt 0 ]]; do
 done
 
 if [[ -f "$OUT_ROOTFS" ]]; then
+  OUT_ROOTFS_WARNING="$(banger_rootfs_manifest_warning "$OUT_ROOTFS" || true)"
+  if [[ -n "$OUT_ROOTFS_WARNING" ]]; then
+    log "warning: $OUT_ROOTFS_WARNING"
+  fi
   log "already exists: $OUT_ROOTFS"
   exit 0
 fi

packages.apt

@@ -0,0 +1,7 @@
+git
+less
+tree
+ca-certificates
+curl
+vim
+tmux

packages.sh

@@ -0,0 +1,115 @@
+#!/usr/bin/env bash
+
+BANGER_PACKAGES_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+BANGER_APT_PACKAGES_FILE="${BANGER_APT_PACKAGES_FILE:-$BANGER_PACKAGES_DIR/packages.apt}"
+
+banger_packages_file() {
+  printf '%s' "$BANGER_APT_PACKAGES_FILE"
+}
+
+banger_packages_normalized_lines() {
+  local packages_file="${1:-$BANGER_APT_PACKAGES_FILE}"
+
+  [[ -f "$packages_file" ]] || return 1
+  awk '
+    {
+      sub(/\r$/, "")
+      sub(/[[:space:]]*#.*$/, "")
+      gsub(/^[[:space:]]+|[[:space:]]+$/, "")
+      if ($0 != "") print
+    }
+  ' "$packages_file"
+}
+
+banger_packages_read_array() {
+  local -n out="$1"
+  local packages_file="${2:-$BANGER_APT_PACKAGES_FILE}"
+
+  mapfile -t out < <(banger_packages_normalized_lines "$packages_file")
+  (( ${#out[@]} > 0 ))
+}
+
+banger_packages_hash_stream() {
+  command -v sha256sum >/dev/null 2>&1 || return 1
+  sha256sum | awk '{print $1}'
+}
+
+banger_packages_manifest_hash() {
+  local packages_file="${1:-$BANGER_APT_PACKAGES_FILE}"
+
+  [[ -f "$packages_file" ]] || return 1
+  banger_packages_normalized_lines "$packages_file" | banger_packages_hash_stream
+}
+
+banger_rootfs_manifest_metadata_path() {
+  local rootfs_path="$1"
+  printf '%s.packages.sha256' "$rootfs_path"
+}
+
+banger_rootfs_manifest_recorded_hash() {
+  local rootfs_path="$1"
+  local metadata_file recorded_hash
+
+  metadata_file="$(banger_rootfs_manifest_metadata_path "$rootfs_path")"
+  [[ -f "$metadata_file" ]] || return 1
+
+  recorded_hash="$(head -n 1 "$metadata_file" | tr -d '[:space:]')"
+  [[ -n "$recorded_hash" ]] || return 1
+  printf '%s' "$recorded_hash"
+}
+
+banger_write_rootfs_manifest_metadata() {
+  local rootfs_path="$1"
+  local manifest_hash="$2"
+  local metadata_file
+
+  metadata_file="$(banger_rootfs_manifest_metadata_path "$rootfs_path")"
+  printf '%s\n' "$manifest_hash" > "$metadata_file"
+}
+
+banger_rootfs_manifest_status() {
+  local rootfs_path="$1"
+  local current_hash recorded_hash
+
+  if [[ ! -f "$rootfs_path" ]]; then
+    printf '%s' "missing-rootfs"
+    return 0
+  fi
+
+  if ! current_hash="$(banger_packages_manifest_hash)"; then
+    printf '%s' "unknown"
+    return 0
+  fi
+
+  if ! recorded_hash="$(banger_rootfs_manifest_recorded_hash "$rootfs_path")"; then
+    printf '%s' "missing-metadata"
+    return 0
+  fi
+
+  if [[ "$recorded_hash" == "$current_hash" ]]; then
+    printf '%s' "fresh"
+  else
+    printf '%s' "stale"
+  fi
+}
+
+banger_rootfs_manifest_warning() {
+  local rootfs_path="$1"
+  local status
+
+  status="$(banger_rootfs_manifest_status "$rootfs_path")"
+  case "$status" in
+    stale)
+      printf '%s was built with an older package manifest; rebuild it explicitly to pick up package changes' "$rootfs_path"
+      ;;
+    missing-metadata)
+      printf '%s has no package manifest metadata; rebuild it explicitly to pick up package changes' "$rootfs_path"
+      ;;
+    unknown)
+      printf 'unable to compare %s against %s; install sha256sum and verify the package manifest manually' "$rootfs_path" "$BANGER_APT_PACKAGES_FILE"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}

restore.sh

@@ -76,8 +76,6 @@ VM_NAME="$(jq -r '.meta.name // empty' "$VM_JSON")"
 PID="$(jq -r '.meta.pid // empty' "$VM_JSON")"
 ROOTFS="$(jq -r '.meta.rootfs // empty' "$VM_JSON")"
 KERNEL="$(jq -r '.meta.kernel // empty' "$VM_JSON")"
-HOME_PATH="$(jq -r '.meta.home_path // empty' "$VM_JSON")"
-VAR_PATH="$(jq -r '.meta.var_path // empty' "$VM_JSON")"
 TAP_DEV="$(jq -r '.meta.tap // empty' "$VM_JSON")"
 API_SOCK="$(jq -r '.meta.api_sock // empty' "$VM_JSON")"
 LOG_FILE="$(jq -r '.meta.log // empty' "$VM_JSON")"
@@ -90,11 +88,11 @@ COW_LOOP_OLD="$(jq -r '.meta.cow_loop // empty' "$VM_JSON")"
 INITRD_PATH="$(jq -r '.config["boot-source"].initrd_path // empty' "$VM_JSON")"
 DNS_NAME="$(banger_dns_name "$VM_NAME")"
 
-if [[ -z "$ROOTFS" || -z "$KERNEL" || -z "$HOME_PATH" || -z "$VAR_PATH" || -z "$API_SOCK" || -z "$TAP_DEV" || -z "$GUEST_IP" || -z "$DM_NAME" || -z "$COW_FILE" ]]; then
+if [[ -z "$ROOTFS" || -z "$KERNEL" || -z "$API_SOCK" || -z "$TAP_DEV" || -z "$GUEST_IP" || -z "$DM_NAME" || -z "$COW_FILE" ]]; then
   log "vm.json missing required fields"
   exit 1
 fi
-if [[ ! -f "$ROOTFS" || ! -f "$KERNEL" || ! -f "$HOME_PATH" || ! -f "$VAR_PATH" || ! -f "$COW_FILE" || ! -f "$FC_BIN" ]]; then
+if [[ ! -f "$ROOTFS" || ! -f "$KERNEL" || ! -f "$COW_FILE" || ! -f "$FC_BIN" ]]; then
   log "missing disk/kernel file(s)"
   exit 1
 fi
@@ -203,9 +201,9 @@ log "configuring machine"
   -d "$(jq -c '.config["machine-config"]' "$VM_JSON")" >/dev/null
 
 boot_args="$(jq -r '.config["boot-source"].boot_args // empty' "$VM_JSON")"
-boot_args="$(printf '%s' "$boot_args" | sed -E 's/(^| )hostname=[^ ]+//g; s/(^| )ip=[^ ]+//g' | awk '{$1=$1; print}')"
+boot_args="$(printf '%s' "$boot_args" | sed -E 's/(^| )hostname=[^ ]+//g; s/(^| )ip=[^ ]+//g; s/(^| )systemd\.mask=home\.mount//g; s/(^| )systemd\.mask=var\.mount//g' | awk '{$1=$1; print}')"
 boot_args="$boot_args ip=${GUEST_IP}::${BR_IP}:255.255.255.0::eth0:off:${DNS_SERVER}"
-boot_args="$boot_args hostname=$VM_NAME"
+boot_args="$boot_args hostname=$VM_NAME systemd.mask=home.mount systemd.mask=var.mount"
 INITRD_JSON=""
 if [[ -n "$INITRD_PATH" ]]; then
   INITRD_JSON=", \"initrd_path\": \"$INITRD_PATH\""
@@ -229,24 +227,6 @@ log "attaching drives"
     \"is_read_only\": false
   }" >/dev/null
 
-/usr/bin/sudo /usr/bin/curl --unix-socket "$API_SOCK" -X PUT http://localhost/drives/home \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"home\",
-    \"path_on_host\": \"$HOME_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
-/usr/bin/sudo /usr/bin/curl --unix-socket "$API_SOCK" -X PUT http://localhost/drives/var \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"var\",
-    \"path_on_host\": \"$VAR_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
 log "configuring network interface"
 /usr/bin/sudo /usr/bin/curl --unix-socket "$API_SOCK" -X PUT http://localhost/network-interfaces/eth0 \
   -H "Content-Type: application/json" \

run.sh

@@ -13,11 +13,10 @@ Options:
   --name <name>        VM name (lowercase letters, digits, -)
   --vcpu <count>       vCPU count (default: 2)
   --ram <mib>          RAM in MiB (default: 1024)
-  --rootfs <path>      Root filesystem image (default: ./rootfs.ext4)
+  --overlay-size <size> Writable overlay size (e.g. 8G, 16384M)
+  --rootfs <path>      Root filesystem image (default: ./rootfs-docker.ext4)
   --kernel <path>      Kernel image (default: ./vmlinux)
   --initrd <path>      Initrd image (optional)
-  --home-size <size>   Home disk size (e.g. 4G, 10240M)
-  --var-size <size>    Var disk size (e.g. 4G, 10240M)
   -h, --help           Show this help
 EOF
 }
@@ -26,6 +25,7 @@ log "starting"
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 source "$DIR/dns.sh"
+source "$DIR/packages.sh"
 STATE="$DIR/state"
 VM_ROOT="$STATE/vms"
 mkdir -p "$VM_ROOT"
@@ -43,20 +43,17 @@ CIDR="24"
 
 DEFAULT_VCPU=2
 DEFAULT_RAM=1024
-DEFAULT_HOME_SIZE="2G"
+DEFAULT_OVERLAY_SIZE="8G"
-DEFAULT_VAR_SIZE="2G"
 MIN_VCPU=1
 MAX_VCPU=16
 MIN_RAM=256
 MAX_RAM=32768
 MAX_DISK_BYTES=$((128 * 1024 * 1024 * 1024))
 DNS_SERVER="1.1.1.1"
-COW_SIZE="2G"
 
 VCPU_COUNT="$DEFAULT_VCPU"
 RAM_MIB="$DEFAULT_RAM"
-HOME_SIZE="$DEFAULT_HOME_SIZE"
+OVERLAY_SIZE="$DEFAULT_OVERLAY_SIZE"
-VAR_SIZE="$DEFAULT_VAR_SIZE"
 KERNEL="$DEFAULT_KERNEL"
 ROOTFS="$DEFAULT_ROOTFS"
 INITRD="$DEFAULT_INITRD"
@@ -105,6 +102,10 @@ while [[ $# -gt 0 ]]; do
       RAM_MIB="${2:-}"
       shift 2
       ;;
+    --overlay-size)
+      OVERLAY_SIZE="${2:-}"
+      shift 2
+      ;;
     --rootfs)
       ROOTFS="${2:-}"
       shift 2
@@ -117,14 +118,6 @@ while [[ $# -gt 0 ]]; do
       INITRD="${2:-}"
       shift 2
       ;;
-    --home-size)
-      HOME_SIZE="${2:-}"
-      shift 2
-      ;;
-    --var-size)
-      VAR_SIZE="${2:-}"
-      shift 2
-      ;;
     -h|--help)
       usage
       exit 0
@@ -155,23 +148,12 @@ if (( RAM_MIB < MIN_RAM || RAM_MIB > MAX_RAM )); then
   exit 1
 fi
 
-HOME_BYTES=""
+if ! OVERLAY_BYTES="$(parse_disk_size "$OVERLAY_SIZE")"; then
-if ! HOME_BYTES="$(parse_disk_size "$HOME_SIZE")"; then
+  log "invalid --overlay-size value: $OVERLAY_SIZE"
-  log "invalid --home-size value: $HOME_SIZE"
   exit 1
 fi
-if (( HOME_BYTES > MAX_DISK_BYTES )); then
+if (( OVERLAY_BYTES > MAX_DISK_BYTES )); then
-  log "home-size exceeds max of $((MAX_DISK_BYTES / 1024 / 1024 / 1024))G"
+  log "overlay-size exceeds max of $((MAX_DISK_BYTES / 1024 / 1024 / 1024))G"
-  exit 1
-fi
-
-VAR_BYTES=""
-if ! VAR_BYTES="$(parse_disk_size "$VAR_SIZE")"; then
-  log "invalid --var-size value: $VAR_SIZE"
-  exit 1
-fi
-if (( VAR_BYTES > MAX_DISK_BYTES )); then
-  log "var-size exceeds max of $((MAX_DISK_BYTES / 1024 / 1024 / 1024))G"
   exit 1
 fi
 
@@ -207,6 +189,12 @@ if [[ ! -f "$ROOTFS" ]]; then
   log "rootfs not found: $ROOTFS"
   exit 1
 fi
+if [[ "$ROOTFS" == "$DEFAULT_ROOTFS" ]]; then
+  ROOTFS_WARNING="$(banger_rootfs_manifest_warning "$ROOTFS" || true)"
+  if [[ -n "$ROOTFS_WARNING" ]]; then
+    log "warning: $ROOTFS_WARNING"
+  fi
+fi
 if [[ ! -f "$KERNEL" ]]; then
   log "kernel not found: $KERNEL"
   exit 1
@@ -248,49 +236,13 @@ sudo -v
 VM_STARTED=0
 CLEANUP_ON_EXIT=0
 KEEP_VM_DIR_ON_FAIL=1
-HOME_PATH="$VM_DIR/home.ext4"
-VAR_PATH="$VM_DIR/var.ext4"
 COW_FILE="$VM_DIR/cow.ext4"
 BASE_LOOP=""
 COW_LOOP=""
 DM_NAME="fc-rootfs-$VM_TAG"
 DM_DEV=""
-SEED_ROOT_MNT="$VM_DIR/mnt-root"
-SEED_HOME_MNT="$VM_DIR/mnt-home"
-SEED_VAR_MNT="$VM_DIR/mnt-var"
 DNS_NAME=""
 
-unmount_if_needed() {
-  local mount_path="$1"
-  [[ -n "$mount_path" ]] || return 0
-  sudo umount "$mount_path" 2>/dev/null || true
-}
-
-seed_volume_from_rootfs() {
-  local source_dir="$1"
-  local target_image="$2"
-  local target_mount="$3"
-  local label="$4"
-
-  if [[ ! -d "$source_dir" ]]; then
-    log "source directory missing in rootfs snapshot: $label"
-    exit 1
-  fi
-
-  mkdir -p "$target_mount"
-  sudo mount "$target_image" "$target_mount"
-  sudo cp -a "$source_dir/." "$target_mount/"
-  sudo umount "$target_mount"
-}
-
-populate_data_disks() {
-  mkdir -p "$SEED_ROOT_MNT" "$SEED_HOME_MNT" "$SEED_VAR_MNT"
-  sudo mount -o ro "$DM_DEV" "$SEED_ROOT_MNT"
-  seed_volume_from_rootfs "$SEED_ROOT_MNT/home" "$HOME_PATH" "$SEED_HOME_MNT" "/home"
-  seed_volume_from_rootfs "$SEED_ROOT_MNT/var" "$VAR_PATH" "$SEED_VAR_MNT" "/var"
-  sudo umount "$SEED_ROOT_MNT"
-}
-
 cleanup() {
   local exit_code=$?
   if [[ "$VM_STARTED" -eq 1 && "$CLEANUP_ON_EXIT" -eq 0 ]]; then
@@ -304,9 +256,6 @@ cleanup() {
     sudo ip link del "$TAP_DEV" 2>/dev/null || true
   fi
   rm -f "${API_SOCK:-}"
-  unmount_if_needed "${SEED_VAR_MNT:-}"
-  unmount_if_needed "${SEED_HOME_MNT:-}"
-  unmount_if_needed "${SEED_ROOT_MNT:-}"
   banger_dns_remove_record_name "${DNS_NAME:-}"
   if [[ -n "${DM_NAME:-}" ]]; then
     sudo dmsetup remove "$DM_NAME" 2>/dev/null || true
@@ -351,15 +300,6 @@ else
   log "setcap not available; firecracker may need root to open TAP"
 fi
 
-if ! command -v mkfs.ext4 >/dev/null 2>&1; then
-  log "mkfs.ext4 required to create home/var disks"
-  exit 1
-fi
-truncate -s "$HOME_BYTES" "$HOME_PATH"
-mkfs.ext4 -F "$HOME_PATH" >/dev/null
-truncate -s "$VAR_BYTES" "$VAR_PATH"
-mkfs.ext4 -F "$VAR_PATH" >/dev/null
-
 if ! command -v dmsetup >/dev/null 2>&1 || ! command -v losetup >/dev/null 2>&1 || ! command -v blockdev >/dev/null 2>&1; then
   log "dmsetup, losetup, and blockdev are required for rootfs snapshots"
   exit 1
@@ -368,23 +308,13 @@ if ! command -v e2cp >/dev/null 2>&1 || ! command -v e2rm >/dev/null 2>&1; then
   log "e2cp and e2rm are required to set hostname and resolv.conf"
   exit 1
 fi
-if ! command -v mount >/dev/null 2>&1 || ! command -v umount >/dev/null 2>&1; then
-  log "mount and umount are required to populate home/var disks"
-  exit 1
-fi
 if ! command -v jq >/dev/null 2>&1; then
   log "jq is required to persist VM metadata"
   exit 1
 fi
 
-COW_BYTES="$(parse_disk_size "$COW_SIZE")"
-if [[ -z "$COW_BYTES" ]]; then
-  log "invalid COW size: $COW_SIZE"
-  exit 1
-fi
-
 BASE_LOOP="$(sudo losetup -f --show --read-only "$ROOTFS")"
-truncate -s "$COW_BYTES" "$COW_FILE"
+truncate -s "$OVERLAY_BYTES" "$COW_FILE"
 COW_LOOP="$(sudo losetup -f --show "$COW_FILE")"
 SECTORS="$(sudo blockdev --getsz "$BASE_LOOP")"
 sudo dmsetup create "$DM_NAME" --table "0 $SECTORS snapshot $BASE_LOOP $COW_LOOP P 8"
@@ -412,9 +342,6 @@ sudo e2cp "$HOSTS_TMP" "$DM_DEV:/etc/hosts" >/dev/null 2>&1 || {
   exit 1
 }
 
-log "populating /home and /var disks from rootfs snapshot"
-populate_data_disks
-
 # Host bridge
 if ! ip link show "$BR_DEV" >/dev/null 2>&1; then
   log "creating host bridge $BR_DEV ($BR_IP/$CIDR)"
@@ -480,7 +407,7 @@ log "configuring machine"
 
 # Boot source
 log "configuring boot source"
-KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0::eth0:off:${DNS_SERVER} hostname=${VM_NAME}"
+KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0::eth0:off:${DNS_SERVER} hostname=${VM_NAME} systemd.mask=home.mount systemd.mask=var.mount"
 
 INITRD_JSON=""
 if [[ -n "$INITRD" ]]; then
@@ -505,28 +432,6 @@ log "attaching root filesystem"
     \"is_read_only\": false
   }" >/dev/null
 
-# Home filesystem
-log "attaching home filesystem"
-"${CURL_CMD[@]}" --unix-socket "$API_SOCK" -X PUT http://localhost/drives/home \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"home\",
-    \"path_on_host\": \"$HOME_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
-# Var filesystem
-log "attaching var filesystem"
-"${CURL_CMD[@]}" --unix-socket "$API_SOCK" -X PUT http://localhost/drives/var \
-  -H "Content-Type: application/json" \
-  -d "{
-    \"drive_id\": \"var\",
-    \"path_on_host\": \"$VAR_PATH\",
-    \"is_root_device\": false,
-    \"is_read_only\": false
-  }" >/dev/null
-
 # Network interface
 log "configuring network interface"
 "${CURL_CMD[@]}" --unix-socket "$API_SOCK" -X PUT http://localhost/network-interfaces/eth0 \
@@ -556,8 +461,6 @@ jq -n \
   --arg log "$LOG_FILE" \
   --arg rootfs "$ROOTFS" \
   --arg kernel "$KERNEL" \
-  --arg home_path "$HOME_PATH" \
-  --arg var_path "$VAR_PATH" \
   --arg base_loop "$BASE_LOOP" \
   --arg cow_file "$COW_FILE" \
   --arg cow_loop "$COW_LOOP" \
@@ -565,7 +468,7 @@ jq -n \
   --arg dm_dev "$DM_DEV" \
   --arg dns_name "$DNS_NAME" \
   --argjson config "$VM_CONFIG_JSON" \
-  '{meta:{id:$id,name:$name,pid:$pid,created_at:$created_at,guest_ip:$guest_ip,tap:$tap,api_sock:$api_sock,log:$log,rootfs:$rootfs,kernel:$kernel,home_path:$home_path,var_path:$var_path,base_loop:$base_loop,cow_file:$cow_file,cow_loop:$cow_loop,dm_name:$dm_name,dm_dev:$dm_dev,dns_name:$dns_name},config:$config}' \
+  '{meta:{id:$id,name:$name,pid:$pid,created_at:$created_at,guest_ip:$guest_ip,tap:$tap,api_sock:$api_sock,log:$log,rootfs:$rootfs,kernel:$kernel,base_loop:$base_loop,cow_file:$cow_file,cow_loop:$cow_loop,dm_name:$dm_name,dm_dev:$dm_dev,dns_name:$dns_name},config:$config}' \
   > "$VM_DIR/vm.json"
 VM_STARTED=1