rc: allow switching runlevels without stopping services

OpenRC, by default, stops all services that are not listed in a runlevel
when rc is used to switch runlevels. This adds a -n/--no-stop command
line option to rc which tells it to skip stopping the services which are
not in the runlevel.

Reported-by: gentoo@thoth.purplefrog.com
X-Gentoo-Bug: 372585
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=372585

src/rc/rc.c

@@ -729,16 +729,18 @@ handle_bad_signal(int sig)
 #include "_usage.h"
 #define usagestring ""					\
     "Usage: rc [options] [<runlevel>]"
-#define getoptstring "a:o:s:S" getoptstring_COMMON
+#define getoptstring "a:no:s:S" getoptstring_COMMON
 static const struct option longopts[] = {
 	{ "applet",   1, NULL, 'a' },
-	{ "override", 1, NULL, 'o' },
-	{ "service",  1, NULL, 's' },
-	{ "sys",      0, NULL, 'S' },
+	{ "no-stop", 0, NULL, 'n' },
+	{ "override",    1, NULL, 'o' },
+	{ "service",     1, NULL, 's' },
+	{ "sys",         0, NULL, 'S' },
 	longopts_COMMON
 };
 static const char * const longopts_help[] = {
 	"runs the applet specified by the next argument",
+	"do not stop any services",
 	"override the next runlevel to change into\n"
 	"when leaving single user or boot runlevels",
 	"runs the service specified with the rest\nof the arguments",
@@ -762,6 +764,7 @@ main(int argc, char **argv)
 	int opt;
 	bool parallel;
 	int regen = 0;
+	bool nostop = false;
 #ifdef __linux__
 	char *proc;
 	char *p;
@@ -812,6 +815,9 @@ main(int argc, char **argv)
 			/* Do nothing, actual logic in run_applets, this
 			 * is a placeholder */
 			break;
+		case 'n':
+			nostop = true;
+			break;
 		case 'o':
 			if (*optarg == '\0')
 				optarg = NULL;
@@ -1022,7 +1028,7 @@ main(int argc, char **argv)
 	parallel = rc_conf_yesno("rc_parallel");
 
 	/* Now stop the services that shouldn't be running */
-	if (stop_services)
+	if (stop_services && !nostop)
 		do_stop_services(newlevel, parallel, going_down);
 
 	/* Wait for our services to finish */