ExecStop

ExecStop is a directive used in systemd unit files to specify commands that should be executed when a unit is stopped. It provides a hook for graceful shutdown and resource cleanup for services and other units managed by systemd.

In a unit file, ExecStop takes a command and its arguments. Multiple ExecStop lines may be declared, and systemd will run them in the order they appear as part of the stop action (for example, when issuing systemctl stop or during system shutdown). These commands are intended to perform tasks such as terminating external processes, closing network connections, releasing resources, or notifying other components that the service is stopping.

ExecStop work is complemented by ExecStopPost, which runs after the main stop sequence has completed to perform additional cleanup tasks that should occur after termination. Together, ExecStop and ExecStopPost provide a two-stage shutdown approach: an immediate stop sequence, followed by post-stop cleanup.

Configuration notes and behavior: ExecStop commands can rely on environment variables such as $MAINPID. They are subject to the unit’s stop-related timing, including TimeoutStopSec and KillMode, which influence how long the stop can take and how processes are terminated. If an ExecStop command exits with a non-zero status, the outcome can affect the overall stop action depending on unit configuration and policy.

Example:

[Service]

ExecStart=/usr/bin/mydaemon

ExecStop=/usr/bin/mydaemon --shutdown

ExecStopPost=/usr/bin/cleanup-sockets

ExecStop is a standard mechanism for implementing graceful shutdown logic within systemd-managed services.