Improve VM lifecycle tooling

Make spawned VMs easier to use and restore from the host.

Add shared DNS and runtime helpers, publish <vm-name>.vm records through mapdns, and teach run/customize/interactive/restore to persist the metadata needed for SSH, DNS cleanup, and clean restores.

Seed per-VM /home and /var disks from the rootfs snapshot so package state is present on first boot, add an interactive customization entrypoint plus ssh.sh and human-friendly list output, and let stop/kill/rm operate on multiple VM identifiers.

Tear down stale TAP, dm, and loop state when VMs stop so restore can recreate them safely, and validate the updated scripts with bash -n plus targeted dry-run harnesses for teardown and restore paths.

customize.sh

@@ -30,6 +30,7 @@ parse_size() {
 }
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$DIR/dns.sh"
 STATE="$DIR/state"
 VM_ROOT="$STATE/vms"
 mkdir -p "$VM_ROOT"
@@ -161,6 +162,7 @@ mkdir -p "$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"
+DNS_NAME=""
 
 # Allocate guest IP
 NEXT_IP_FILE="$STATE/next_ip"
@@ -174,6 +176,7 @@ cleanup() {
   sudo kill "${FC_PID:-}" 2>/dev/null || true
   sudo ip link del "$TAP_DEV" 2>/dev/null || true
   rm -f "$API_SOCK"
+  banger_dns_remove_record_name "${DNS_NAME:-}"
   rm -rf "$VM_DIR"
 }
 trap cleanup EXIT
@@ -211,23 +214,6 @@ for _ in $(seq 1 200); do
 done
 [[ -S "$API_SOCK" ]] || { log "firecracker api socket not ready"; exit 1; }
 
-VM_CONFIG_JSON="$(sudo -E curl --unix-socket "$API_SOCK" -sS http://localhost/vm/config)"
-CREATED_AT="$(date -Iseconds)"
-jq -n \
-  --arg id "$VM_ID" \
-  --arg name "$VM_NAME" \
-  --arg pid "$FC_PID" \
-  --arg created_at "$CREATED_AT" \
-  --arg guest_ip "$GUEST_IP" \
-  --arg tap "$TAP_DEV" \
-  --arg api_sock "$API_SOCK" \
-  --arg log "$LOG_FILE" \
-  --arg rootfs "$OUT_ROOTFS" \
-  --arg kernel "$KERNEL" \
-  --argjson config "$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},config:$config}' \
-  > "$VM_DIR/vm.json"
-
 log "configuring machine"
 sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/machine-config \
   -H "Content-Type: application/json" \
@@ -271,6 +257,31 @@ sudo -E curl --unix-socket "$API_SOCK" -X PUT http://localhost/actions \
   -H "Content-Type: application/json" \
   -d '{ "action_type": "InstanceStart" }' >/dev/null
 
+SUDO_CHILD_PID="$(pgrep -n -f "$API_SOCK" || true)"
+if [[ -n "$SUDO_CHILD_PID" ]]; then
+  FC_PID="$SUDO_CHILD_PID"
+fi
+
+VM_CONFIG_JSON="$(sudo -E curl --unix-socket "$API_SOCK" -sS http://localhost/vm/config)"
+CREATED_AT="$(date -Iseconds)"
+DNS_NAME="$(banger_dns_name "$VM_NAME")"
+banger_dns_write_record "$VM_NAME" "$GUEST_IP"
+jq -n \
+  --arg id "$VM_ID" \
+  --arg name "$VM_NAME" \
+  --arg pid "$FC_PID" \
+  --arg created_at "$CREATED_AT" \
+  --arg guest_ip "$GUEST_IP" \
+  --arg tap "$TAP_DEV" \
+  --arg api_sock "$API_SOCK" \
+  --arg log "$LOG_FILE" \
+  --arg rootfs "$OUT_ROOTFS" \
+  --arg kernel "$KERNEL" \
+  --arg dns_name "$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:$kernel,dns_name:$dns_name},config:$config}' \
+  > "$VM_DIR/vm.json"
+
 log "enabling NAT for customization"
 sudo -E ./nat.sh up "$VM_TAG" >/dev/null