Make possible to daemonize lxc-start

If needed the container can be launched in background
with a specific option -d.

That will make mute the container, the logs can help
to check what went wrong.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

doc/lxc-start.sgml.in

@@ -74,6 +74,29 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 
   </refsect1>
 
+  <refsect1>
+
+    <title>Options</title>
+
+    <variablelist>
+
+      <varlistentry>
+	<term>
+	  <option>-d, --daemon</option>
+	</term>
+	<listitem>
+	  <para>
+	    Run the container as a daemon. As the container has no
+	    more tty, if an error occurs nothing will be displayed,
+	    the log file can be used to check the error.
+	  </para>
+	</listitem>
+      </varlistentry>
+
+    </variablelist>
+
+  </refsect1>
+
   &commonoptions;
 
   <refsect1>
@@ -102,7 +125,6 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
         </listitem>
       </varlistentry>    
 
-
     </variablelist>
 
   </refsect1>

src/lxc/arguments.h

@@ -42,6 +42,7 @@ struct lxc_arguments {
 	char *log_file;
 	char *log_priority;
 	int quiet;
+	int daemonize;
 	const char *rcfile;
 	const char *statefile;
 

src/lxc/lxc_start.c

@@ -26,11 +26,13 @@
 #include <string.h>
 #include <termios.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <signal.h>
 #include <sys/param.h>
 #include <sys/utsname.h>
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <arpa/inet.h>
 #include <netinet/in.h>
 #include <net/if.h>
@@ -41,7 +43,16 @@
 
 lxc_log_define(lxc_start, lxc);
 
+static int my_parser(struct lxc_arguments* args, int c, char* arg)
+{
+	switch (c) {
+	case 'd': args->daemonize = 1; break;
+	}
+	return 0;
+}
+
 static const struct option my_longopts[] = {
+	{"daemon", no_argument, 0, 'd'},
 	LXC_COMMON_OPTIONS
 };
 
@@ -53,10 +64,12 @@ static struct lxc_arguments my_args = {
 lxc-start start COMMAND in specified container NAME\n\
 \n\
 Options :\n\
-  -n, --name=NAME      NAME for name of the container",
-	.options  = my_longopts,
-	.parser   = NULL,
-	.checker  = NULL,
+  -n, --name=NAME      NAME for name of the container\n\
+  -d, --daemon         daemonize the container",
+	.options   = my_longopts,
+	.parser    = my_parser,
+	.checker   = NULL,
+	.daemonize = 0,
 };
 
 static int save_tty(struct termios *tios)
@@ -122,6 +135,11 @@ int main(int argc, char *argv[])
 			 my_args.progname, my_args.quiet))
 		return err;
 
+	if (my_args.daemonize && daemon(0 ,0)) {
+		SYSERROR("failed to daemonize '%s'", my_args.name);
+		return err;
+	}
+
 	save_tty(&tios);
 
 	err = lxc_start(my_args.name, args);