diff --git a/cmd/runsvc/runsvc.c b/cmd/runsvc/runsvc.c
index a8e5bb2..9e646e7 100644
--- a/cmd/runsvc/runsvc.c
+++ b/cmd/runsvc/runsvc.c
@@ -17,17 +17,20 @@
  */
 #include "runsvc.h"
 
-static int setup_tty(const char *ctty)
+static int setup_tty(service_t *svc)
 {
 	int fd;
 
-	if (ctty != NULL) {
-		fd = open(ctty, O_RDWR);
+	if (svc->ctty != NULL) {
+		fd = open(svc->ctty, O_RDWR);
 		if (fd < 0) {
-			perror(ctty);
+			perror(svc->ctty);
 			return -1;
 		}
 
+		if (svc->flags & SVC_FLAG_TRUNCATE_OUT)
+			ftruncate(fd, 0);
+
 		close(STDIN_FILENO);
 		close(STDOUT_FILENO);
 		close(STDERR_FILENO);
@@ -125,7 +128,7 @@ int main(int argc, char **argv)
 	if (initenv())
 		goto out;
 
-	if (setup_tty(svc->ctty))
+	if (setup_tty(svc))
 		goto out;
 
 	if (svc->exec->next == NULL)
diff --git a/lib/include/service.h b/lib/include/service.h
index 49c5432..03d768e 100644
--- a/lib/include/service.h
+++ b/lib/include/service.h
@@ -51,6 +51,11 @@ enum {
 	RDSVC_NO_DEPS = 0x08,	/* do not store dependencies */
 };
 
+enum {
+	/* truncate stdout */
+	SVC_FLAG_TRUNCATE_OUT = 0x01,
+};
+
 typedef struct exec_t {
 	struct exec_t *next;
 	int argc;		/* number of elements in argument vector */
@@ -67,6 +72,7 @@ typedef struct service_t {
 	char *desc;		/* description string */
 	char *ctty;		/* controlling tty or log file */
 	int rspwn_limit;	/* maximum respawn count */
+	unsigned int flags;	/* SVC_FLAG_* bit field */
 
 	/* linked list of command lines to execute */
 	exec_t *exec;
diff --git a/lib/util/rdsvc.c b/lib/util/rdsvc.c
index 6a964f7..37c7ba0 100644
--- a/lib/util/rdsvc.c
+++ b/lib/util/rdsvc.c
@@ -70,8 +70,16 @@ static int svc_desc(service_t *svc, char *arg, rdline_t *rd)
 
 static int svc_tty(service_t *svc, char *arg, rdline_t *rd)
 {
+	if (strncmp(arg, "truncate", 8) == 0 && isspace(arg[8])) {
+		svc->flags |= SVC_FLAG_TRUNCATE_OUT;
+		arg += 8;
+		while (isspace(*arg))
+			++arg;
+	}
+
 	if (try_unescape(arg, rd))
 		return -1;
+
 	svc->ctty = try_strdup(arg, rd);
 	return svc->ctty == NULL ? -1 : 0;
 }