Add fleet hostnaming

diskless.pkr.hcl

@@ -296,6 +296,15 @@ build {
       # ---- Diskless adaptations ------------------------------------------
       # Per-host machine-id is generated at boot into the overlay
       "truncate -s 0 /etc/machine-id",
+      # No per-host hostname in the image (image stays fleet-generic): empty
+      # /etc/hostname so the static hostname is unset and NetworkManager sets the
+      # transient hostname from the DHCP lease — DHCP option 12 (the dnsmasq
+      # fleet-namer assigns a creative name per MAC, server-side) or a reverse-DNS
+      # PTR lookup. hostname-mode=default makes that explicit so a stricter global
+      # config can't switch it to 'none' and leave hosts unnamed.
+      "truncate -s 0 /etc/hostname",
+      "install -D -m0644 /tmp/etc-stage/NetworkManager/conf.d/20-hostname.conf /etc/NetworkManager/conf.d/20-hostname.conf",
+      "restorecon /etc/NetworkManager/conf.d/20-hostname.conf",
       # Read-only erofs/verity root; runtime state on a tmpfs overlay provided
       # by systemd.volatile=overlay (set in the cmdline by extract-artifacts.sh).
       # RHEL/Rocky dracut has no 'overlayfs'/'rootovl' module.