-i case goes to background pause and acts like -a case on receiving

SIGTERM. This helps to keep CMOS clock updated before reboot.
Idea from J.Wunsch.

sbin/adjkerntz/adjkerntz.8

@@ -53,18 +53,24 @@ initialization call from
 .Pa /etc/rc
 (before any daemons are started).
 .Nm Adjkerntz
-makes the first adjustment and the initial time zone offset is stored into
+makes the adjustment of kernel clock (CMOS clock not touched)
+and the initial time zone offset is stored into
 .Pa adjkerntz
 kernel variable
 for following subsequent
-.Nm adjkerntz
-calls.
+.Nm "'adjkerntz -a'"
+calls. Then it goes to background pause which ends with SIGTERM.
+After receiving SIGTERM it acts like
+.Nm "'adjkerntz -a'"
+to be shure to have proper CMOS clock before reboot.
 .It Cm Fl a
 This form is needed, when time zone changes occur.
 .Nm Adjkerntz
 uses the previously stored
 time zone offset and the changed time zone rule to
-produce the new time zone offset, fix the RTC clock and store the new
+produce the new time zone offset, fix the CMOS clock
+(kernel clock not touched)
+and store the new
 offset into
 .Pa adjkerntz
 kernel variable
@@ -73,6 +79,7 @@ It is recommended to use this form in root's
 .Xr crontab 5
 every half of a hour from 0am to 4am
 since this times matches most modern time zone changes.
+.El
 .Pp
 .Nm Adjkerntz
 clears the kernel timezone structure and makes kernel always run at UTC

sbin/adjkerntz/adjkerntz.c

@@ -41,6 +41,7 @@ char copyright[] =
  *
  */
 #include <stdio.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <syslog.h>
@@ -54,6 +55,8 @@ char copyright[] =
 
 #define REPORT_PERIOD (30*60)
 
+void fake() {}
+
 int main(argc, argv)
 	int argc;
 	char **argv;
@@ -69,6 +72,7 @@ int main(argc, argv)
 	time_t initial_sec, final_sec;
 	int ch, init = -1;
 	int disrtcset, need_restore = 0;
+	sigset_t mask, emask;
 
 	while ((ch = getopt(argc, argv, "ai")) != EOF)
 		switch((char)ch) {
@@ -95,10 +99,24 @@ int main(argc, argv)
 	if (access(_PATH_CLOCK, F_OK))
 		return 0;
 
+	sigemptyset(&mask);
+	sigemptyset(&emask);
+	sigaddset(&mask, SIGTERM);
+
 	openlog("adjkerntz", LOG_PID|LOG_PERROR, LOG_DAEMON);
 
+	(void) signal(SIGHUP, SIG_IGN);
+
+	if (init && daemon(0, 1)) {
+		syslog(LOG_ERR, "daemon: %m");
+		return 1;
+	}
+
 again:
 
+	(void) sigprocmask(SIG_BLOCK, &mask, NULL);
+	(void) signal(SIGTERM, fake);
+
 /****** Critical section, do all things as fast as possible ******/
 
 	/* get local CMOS clock and possible kernel offset */
@@ -126,6 +144,8 @@ again:
 		 */
 		syslog(LOG_WARNING,
 		"Nonexistent local time -- will retry after %d secs", REPORT_PERIOD);
+		(void) signal(SIGTERM, SIG_DFL);
+		(void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
 		(void) sleep(REPORT_PERIOD);
 		goto again;
 	}
@@ -165,6 +185,8 @@ again:
 			 */
 			syslog(LOG_WARNING,
 		"Nonexistent (final) local time -- will retry after %d secs", REPORT_PERIOD);
+			(void) signal(SIGTERM, SIG_DFL);
+			(void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
 			(void) sleep(REPORT_PERIOD);
 			goto again;
 		}
@@ -241,5 +263,12 @@ again:
 
 /****** End of critical section ******/
 
+	if (init) {
+		init = 0;
+		/* wait for signals and acts like -a */
+		(void) sigsuspend(&emask);
+		goto again;
+	}
+
 	return 0;
 }