diff --git a/daemon/.gitignore b/daemon/.gitignore
index 6693f26..fa58ad5 100644
--- a/daemon/.gitignore
+++ b/daemon/.gitignore
@@ -4,3 +4,4 @@ alix-usv
 alix-usvd
 alix-usvd.sock
 alix-usvd.log
+alix-usvd.pid
diff --git a/daemon/Makefile b/daemon/Makefile
index 42bb51f..a280870 100644
--- a/daemon/Makefile
+++ b/daemon/Makefile
@@ -6,7 +6,7 @@ CFLAGS = -Wall -O2 -MD -MP -MF $(*F).d
 # ------
 
 SRC1 := alix-usv.c logging.c unixsocket.c
-SRC2 := alix-usvd.c configfile.c event.c logging.c unixsocket.c
+SRC2 := alix-usvd.c configfile.c event.c logging.c pidfile.c unixsocket.c
 
 all: $(TARGET1) $(TARGET2)
 
@@ -23,6 +23,6 @@ $(TARGET2): $(SRC2:.c=.o)
 	@$(CC) -c $(CFLAGS) $< -o $@
 
 clean:
-	rm -rf $(TARGET1) $(TARGET2) *.o *.d *.log *.sock
+	rm -rf $(TARGET1) $(TARGET2) *.o *.d *.log *.sock *.pid
 
 -include $(shell find . -name \*.d 2> /dev/null)
diff --git a/daemon/alix-usvd.c b/daemon/alix-usvd.c
index ed3af1f..c463d73 100644
--- a/daemon/alix-usvd.c
+++ b/daemon/alix-usvd.c
@@ -34,6 +34,7 @@
 #include "configfile.h"
 #include "event.h"
 #include "logging.h"
+#include "pidfile.h"
 #include "unixsocket.h"
 
 /* eeprom parameters / thresholds & defaults */
@@ -41,6 +42,7 @@
 
 #define DEFAULT_CONFIG "alix-usvd.conf"
 #define DEFAULT_LOGFILE "alix-usvd.log"
+#define DEFAULT_PIDFILE "alix-usvd.pid"
 #define DEFAULT_SOCKET "alix-usvd.sock"
 
 enum {
@@ -370,7 +372,12 @@ int main(int argc, char *argv[])
 		exit(1);
 
 	if (debug == 0) {
-		/* TODO: check PID-file */
+		/* check pidfile */
+		const char *pidfile = config_get_string("global", "pidfile", DEFAULT_PIDFILE);
+		if (pidfile_check(pidfile, 1) != 0) {
+			log_print(LOG_ERROR, "alix-usvd already running");
+			exit(1);
+		}
 
 		/* start logging */
 		const char *logfile = config_get_string("global", "logfile", DEFAULT_LOGFILE);
@@ -380,7 +387,11 @@ int main(int argc, char *argv[])
 		/* zum daemon mutieren */
 		daemon(-1, 0);
 
-		/* TODO: write PID-file */
+		/* create pidfile */
+		if (pidfile_create(pidfile) < 0) {
+			log_print(LOG_ERROR, "failed to create pidfile %s", pidfile);
+			exit(1);
+		}
 	}
 
 	log_print(LOG_INFO, "alix-usvd started (pid: %d)", getpid());
diff --git a/daemon/pidfile.c b/daemon/pidfile.c
new file mode 100644
index 0000000..9de2d3d
--- /dev/null
+++ b/daemon/pidfile.c
@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <signal.h>
+
+#include "logging.h"
+
+int pidfile_create(const char *filename)
+{
+	int fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0644);
+	if (fd < 0)
+		return -1;
+
+	char buf[8];
+	int len = snprintf(buf, sizeof(buf), "%d", getpid());
+	write(fd, buf, len);
+
+	close(fd);
+	return 0;
+}
+
+int pidfile_remove(const char *filename)
+{
+	return unlink(filename);
+}
+
+pid_t pidfile_check(const char *filename, int remove_stale)
+{
+	int fd = open(filename, O_RDWR);
+	if (fd < 0) {
+		if (errno == ENOENT) {
+			errno = 0;
+			return 0;
+		}
+		return -1;
+	}
+
+	char buf[9];
+	int len = read(fd, buf, sizeof(buf) -1);
+	buf[len] = '\0';
+
+	char *tmp;
+	pid_t pid = strtol(buf, &tmp, 10);
+	if (len == 0 || tmp == buf)
+		pid = -1;
+
+	/* just return the pid */
+	if (!remove_stale)
+		return pid;
+
+	/* invalid pid, remove stale file */
+	if (pid == -1) {
+		pidfile_remove(filename);
+		return 0;
+	}
+
+	/* check if pid is still running */
+	if (kill(pid, 0) == 0 || errno != ESRCH) {
+		errno = 0;
+		return pid;
+	}
+
+	errno = 0;
+	pidfile_remove(filename);
+	return 0;
+}
diff --git a/daemon/pidfile.h b/daemon/pidfile.h
new file mode 100644
index 0000000..2ba1512
--- /dev/null
+++ b/daemon/pidfile.h
@@ -0,0 +1,11 @@
+#ifndef _PIDFILE_H_
+#define _PIDFILE_H_
+
+#include <sys/types.h>
+
+int pidfile_create(const char *filename);
+int pidfile_remove(const char *filename);
+
+pid_t pidfile_check(const char *filename, int remove_stale);
+
+#endif // _PIDFILE_H_