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Sim by rConfig Sim by rConfig rcfg-sim

System install with systemd

For anything beyond a loopback trial you run rcfg-sim as systemd template services — one instance per IP alias — with kernel and file-descriptor tuning applied. make install handles all of it.

What make install does

Section titled “What make install does”
Terminal window
sudo make install

This (re)builds the binaries and installs:

  • Binaries into /opt/rcfg-sim/
  • The systemd template unit rcfg-sim@.service into /etc/systemd/system/
  • A sysctl drop-in into /etc/sysctl.d/ (kernel tuning)
  • An FD-limits drop-in into /etc/security/limits.d/
  • Config under /etc/rcfg-sim/ (host key, per-instance env files)

A dedicated unprivileged service account (rcfgsim) runs the processes.

One instance per IP

Section titled “One instance per IP”

The unit is a template (rcfg-sim@.service). The instance name is the IP the service binds, and each instance reads its own environment file:

Terminal window
# Enable + start an instance bound to 10.50.0.1
sudo systemctl enable --now rcfg-sim@10.50.0.1.service


# Status / logs
systemctl status rcfg-sim@10.50.0.1.service
journalctl -u rcfg-sim@10.50.0.1.service -f

Each instance is independent — you can restart or drain one IP’s 2,500 ports without touching the rest of the fleet. Configuration comes from /etc/rcfg-sim/<IP>.env (see Running the server for the variables, modeled on deploy/systemd/rcfg-sim-instance.env.sample).

Kernel tuning and limits

Section titled “Kernel tuning and limits”

High-density listeners need a wider kernel envelope. The installed sysctl drop-in raises, among others:

  • fs.file-max (to ~2,000,000)
  • net.core.somaxconn
  • net.ipv4.tcp_tw_reuse
  • net.ipv4.ip_local_port_range (widened)
  • ARP table sizing for many local addresses

The limits drop-in sets nofile = 200000 for the rcfgsim user, and the unit sets LimitNOFILE=200000. The unit also drains gracefully on stop (SIGTERM, TimeoutStopSec=45s) so in-flight sessions finish cleanly.

Graceful shutdown

Section titled “Graceful shutdown”

The service stops with a SIGTERM and a 45-second drain window. The server stops accepting new connections, lets active sessions complete, and exits — see Concurrency & graceful drain.

Uninstall

Section titled “Uninstall”
Terminal window
sudo make uninstall

Stops and disables the units and removes the installed binaries and config drop-ins.

Next

Section titled “Next”