Linux

Linux - Process Signals SIGINT, SIGTERM, SIGKILL, SIGQUIT, and SIGTSTP Explained

NIC

Posted by Rico's Nerd Cluster on January 29, 2018
Signal Number Description Keyboard How it’s sent / Source Handling / Behavior
SIGINT 2 Interactive interrupt Ctrl + C Terminal foreground interrupt Graceful shutdown if handled; stop work, clean exit
SIGTERM 15 Graceful stop request None kill <pid>, systemd stop, docker stop Begin graceful shutdown; drain work, flush state
SIGKILL 9 Forced termination None kill -9 <pid>, supervisor timeout Immediate kernel termination; no cleanup possible
SIGQUIT 3 Quit + core dump Ctrl + \ Terminal foreground interrupt Terminate process and write core dump
SIGTSTP 20 Suspend (job control stop) Ctrl + Z Terminal job control Process is stopped; can be resumed with fg / bg

Notes worth remembering

  • Only SIGKILL (9) cannot be handled or intercepted.
  • SIGQUIT is useful for post-mortem debugging via core dumps.
  • SIGTSTP does not terminate the process; it pauses it.
  • Well-behaved services typically handle SIGINT and SIGTERM the same way.
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