Linux supports both POSIX reliable signals and POSIX real-time signals.
Signal Dispositions: Each signal has a current disposition, which determines how the process behaves when it is delivered the signal.
We have different types of signals in Linux
The specified default disposition of few signals are below:
Term : default action is to terminate the process.
Ign : default action is to ignore the signal.
Stop : default action is to stop the process.
Cont : default action is to continue the process if it is currently stopped.
List of few standard signals :
Name Default Action Description
SIGHUP Terminate Process Terminal line hangup
SIGINT Terminate Process Interrupt program
SIGQUIT Create Core Image Quit Program
SIGABRT Create Core Image Abort Program
SIGKILL Terminate Process Kill Program
SIGTERM Terminate Process Software Termination Signal
SIGUSR1 Terminate Process User Defined Signal 1
SIGUSR2 Terminate Process User Defined Signal 2
Note: The signal SIGKILL and SIGSTOP cannot be caught, blocked or ignored.
Case Study: Handle Sigterm Signal in docker container and terminate the process gracefully.
Let suppose we need to run scala application inside our container and based on the signal received we need to handle it and terminate the application gracefully.
Suppose our Dockerfile has an entrypoint as:
ENTRYPOINT [“/bin/bash”, “blog.sh”]
inside our blog.sh script we need to trap the Signal and handle it based on the use case of the case study.