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How to use the signals map
1
Identify the signal you need
Browse the interactive table with number, name, default action and description of each signal.
2
Use the quick filter
Search by name (SIGTERM, SIGKILL) or number (9, 15) to instantly locate any signal.
3
Understand the default action
Each signal shows Term (terminates), Core (dump + terminate), Stop (pauses) or Cont (resumes).
4
Apply the signal with kill
Run kill -<signal> <PID> (e.g. kill -15 1234 or kill -9 1234) in your terminal.
Default actions of signals
- Term: Terminates the process normally
- Core: Generates a core dump and terminates the process
- Stop: Stops the process (puts it in background)
- Cont: Continues a stopped process
- Ign: The signal is ignored
Frequently Asked Questions
What is the difference between kill -9 and kill -15?
kill -15 (SIGTERM) sends a polite termination signal that the process can intercept to perform cleanup (close files, release resources) before exiting. kill -9 (SIGKILL) kills the process immediately and unconditionally — the process cannot ignore or handle it. Always try SIGTERM first and use SIGKILL only as a last resort.
What is SIGINT and how is it different from SIGTERM?
SIGINT (Signal Interrupt, signal 2) is sent when you press Ctrl+C in the terminal. It directly interacts with the foreground process. SIGTERM (signal 15) is sent via the kill command and can target any process. Both can be handled by the process, but SIGINT is specifically associated with keyboard interruption.
What do SIGSTOP and SIGCONT do?
SIGSTOP (signal 19) stops process execution similarly to Ctrl+Z. The process cannot ignore this signal. SIGCONT (signal 18) resumes a process that was stopped with SIGSTOP or SIGTSTP (Ctrl+Z). These signals are useful for pausing and resuming processes without terminating them.
Which signal should I use to reload a program's configuration?
SIGHUP (Signal Hang Up, signal 1) is the standard signal that many processes (like nginx, sshd, systemd) use to reload their configuration files without restarting. For example: kill -HUP $(cat /var/run/nginx.pid) makes nginx reload its configuration without interrupting service.
Which signals cannot be ignored by a process?
SIGKILL (signal 9) and SIGSTOP (signal 19) cannot be ignored, handled or blocked by any process. SIGKILL kills the process immediately and unconditionally. SIGSTOP stops (pauses) the process until it receives SIGCONT. Both are last-resort signals: SIGKILL to force termination, SIGSTOP to pause without killing.
How to list all available signals in Linux?
You can list all available signals with the kill -l command in your terminal. This displays signal names (from SIGABRT to SIGSYS). You can also see each signal number with kill -l or check /usr/include/asm-generic/signal.h. There are 31 standard signals in Linux (1-31), plus real-time signals (32-64) used for inter-process communication.