Linux

Yes; the command prefix that you're looking for is

shutdown now ; (followed by your sudo command if you wish)

It will provide the appropriate delay before using the root command via sudo or having logged again as root (sigh)!

Sure, though I advise against it. The following C program can do that:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char **argv) {
	if (argc < 2) {
		fprintf(stderr, "usage: %s <command> <args>...", argv[0]);
		return EXIT_FAILURE;
	}

	printf("Executing");
	for (int i = 1; i < argc; ++i) {
		printf(" %s", argv[i]);
	}
	puts("\nPress ^C to abort.");
	sleep(5);

	if (setuid(0)) {
		perror("setuid");
		return EXIT_FAILURE;
	}

	execvp(argv[1], argv + 1);
	perror(argv[1]);
	return EXIT_FAILURE;
}

As seen in:

$ gcc -O2 -o delay-su delay-su.c
$ sudo chown root:sudo delay-su
$ sudo chmod 4750 delay-su
$ ./delay-su id
$ id -u
1000
$ ./delay-su id -u
Executing id -u
^C to abort
0

This will allow anyone in group sudo to execute any command as root. You may change the group to something else to control who exactly can run the program (you cannot change the user of the program).

If there’s some specific command you want to run, it’s better to hard-code it or configure sudo to allow execution of that command without password.

I can’t find anything that quite fits your requirements.

Putting a NOPASSWD option on your sudo config should cover the removal of the password requirement, but this may be ill -advised; it is probably wiser to increase the timestamp_timeout duration.

The intentional delay is tougher, and for that it looks like you’d need to write a PAM module. pam_faildelay is very close to what you need, you’d just need to make it produce a delay on success as well as failure.

What purpose should this fulfil? If you are unsure whether your command is correct, double-check it before hitting the ENTER key.

sure. first, configure sudo to be passwordless, or perhaps just to stay unlocked for longer (it's easy to find instructions for how to do that).

then, put this in your ~/.bashrc:

alias sudo='echo -n "are you sure? "; for i in $(seq 5); do echo -n "$((6 - $i)) "; sleep 1; done && echo && /usr/bin/sudo '

Now "sudo" will give you a 5 second countdown (during which you can hit ctrl-c if you change your mind) before running whatever command you ask it to.

@dontblink You would have to write a PAM module to do that