diff --git a/sbin/reboot/reboot.8 b/sbin/reboot/reboot.8
--- a/sbin/reboot/reboot.8
+++ b/sbin/reboot/reboot.8
@@ -110,6 +110,15 @@
 .Va value
 contains any characters that are special to the shell or loader's configuration
 parsing code.
+.It Fl f
+Force reboot.
+Normally,
+.Nm
+checks for the presence of the next kernel,
+and absence of the
+.Pa /var/run/noshutdown
+file.
+Without this flag, reboot is denied if one of the conditions failed.
 .It Fl k Ar kname
 Boot the specified kernel
 .Ar kname
diff --git a/sbin/reboot/reboot.c b/sbin/reboot/reboot.c
--- a/sbin/reboot/reboot.c
+++ b/sbin/reboot/reboot.c
@@ -40,6 +40,7 @@
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <paths.h>
 #include <pwd.h>
 #include <signal.h>
 #include <spawn.h>
@@ -222,6 +223,7 @@
 {
 	struct utmpx utx;
 	const struct passwd *pw;
+	struct stat st;
 	int ch, howto = 0, i, sverrno;
 	bool Dflag, fflag, lflag, Nflag, nflag, qflag;
 	uint64_t pageins;
@@ -294,6 +296,11 @@
 	if (argc != 0)
 		usage();
 
+	if (!donextboot && !fflag && stat(_PATH_NOSHUTDOWN, &st) == 0) {
+		errx(1, "Reboot cannot be done, " _PATH_NOSHUTDOWN
+		    " is present");
+	}
+
 	if (Dflag && ((howto & ~RB_HALT) != 0  || kernel != NULL))
 		errx(1, "cannot delete existing nextboot config and do anything else");
 	if ((howto & (RB_DUMP | RB_HALT)) == (RB_DUMP | RB_HALT))