how to generate core file in docker container?

Question

using ulimit command, i set core file size.

ulimit -c unlimited

and I compiled c source code using gcc - g option. then a.out generated. after comm

Answer 1

If you want to generate a core dump of an existing process, say using gcore, you need to start the container with --cap-add=SYS_PTRACE to allow a debugger running as root inside the container to attach to the process. (For core dumps on signals, see the other answer)