The same is true for the process group/session + controlling terminal solution: the solution doesn't work recursively (can't do process management downstream),

The same is true for the process group/session + controlling terminal solution: the solution doesn't work recursively (can't do process management downstream), and it also requires child processes to abstain from changing SIGHUP handler or mask, but in the vast majority most cases none of those limitations are a problem. Combined with POSIX fcntl locks[1] on a PID file, this is my go to generic solution for Unix-portable[2], multiprocess daemons. The amount of code required in the supervisor component is quite trivial, yet covers almost all of your bases. [1] fcntl locks permit querying the PID of the lock holder, so you don't need to write the PID to the file, providing a solution to the PID file race and loaded gun dilemmas. (There's still a race, but the same race exists with Linux containers, and both can be resolved in similar manner--query PID, send SIGSTOP, verify PID association, send SIGKILL or SIGCONT.) [2] One of the crucial behaviors, that the kernel atomically sends SIGHUP to all processes in the group if the controlling process terminates, isn't guaranteed by POSIX, but it's the behavior on all Unix I've tried--AIX, FreeBSD, macOS, Linux, NetBSD, OpenBSD, and Solaris.