Debian 13 tmpfs /tmp causes OOM in small containers
Debian 13 mounts /tmp as tmpfs sized to host RAM (not container cgroup). A 512MB container on a 256GB host OOM-kills on apt installs. Fix: `systemctl mask tmp.mount` then reboot.
Mask the tmpfs mount immediately after creating any small-memory Debian 13 LXC.
Discovered during Samba deployment (2026-02-28).