Add support for single (S) user mode from kernel cmdline

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/conf.c

@@ -81,6 +81,9 @@ void conf_parse_cmdline(void)
 
 		if (string_compare(tok, "rescue") || string_compare(tok, "recover"))
 			rescue = 1;
+
+		if (string_compare(tok, "single") || string_compare(tok, "S"))
+			single = 1;
 	}
 	fclose(fp);
 
@@ -628,6 +631,10 @@ done:
 	/* Drop record of all .conf changes */
 	drop_changes();
 
+	/* Override configured runlevel, user said 'S' on /proc/cmdline */
+	if (BOOTSTRAP && single)
+		cfglevel = 1;
+
 	/*
 	 * Set host name, from %DEFHOST, *.conf or /etc/hostname.  The
 	 * latter wins, if neither exists we default to "noname"