I published three Rust crates: name-to-handle-at: Safe, low-level Rust bindings for Linux name_to_handle_at and open_by_handle_at system calls pidfd-util: Safe Rust wrapper for Linux process file descriptors (pidfd) listen-fds: A Rust library for handling systemd socket activation They might seem like rather arbitrary, unconnected things – but there is a connection! systemd socket activation passes file descriptors and a bit of metadata as environment variables to the activated process. If the activated process exec’s another program, the file descriptors get passed along because they are not CLOEXEC. If that process then picks them up, things could go very wrong. So, the activated process is supposed to mark the file descriptors CLOEXEC, and unset the socket activation environment variables. If a process doesn’t do this for whatever reason however, the same problems can arise. So there is another mechanism to help prevent it: another bit of metadata contains the PID of the target. Processes can check it against their own PID to figure out if they were the target of the activation, without having to depend on all other processes doing the right thing.