diff --git a/software/infnoise.c b/software/infnoise.c
index b556b58..bc3126b 100644
--- a/software/infnoise.c
+++ b/software/infnoise.c
@@ -290,8 +290,8 @@ int main(int argc, char **argv)
             xArg++;
             opts.serial = argv[xArg];
             if(opts.serial == NULL || !strcmp("",opts.serial)) {
-                fputs("--serial without value\n", stderr);
-                return 1;
+		opts.serial = NULL;
+                fputs("WARNING: --serial without value\n", stderr);
             }
         } else if(!strcmp(argv[xArg], "--daemon")) {
             opts.daemon = true;
diff --git a/software/init_scripts/README.md b/software/init_scripts/README.md
index d657630..e32a3c3 100644
--- a/software/init_scripts/README.md
+++ b/software/init_scripts/README.md
@@ -14,6 +14,7 @@ which start the service when the Infinite Noise TRNG is connected and also stops
 - `infnoise.openrc`: OpenRC, ?
 - `infnoise.conf`: Upstart, tested in Ubuntu 14.04, 16.04 (requires upstart install)
 - `infnoise.service`: Systemd, works for CentOS, Ubuntu, Debian, ArchLinux
-- `infnoise.service.bin`: Same as infnoise.service, binary path = /usr/bin/
-- `infnoise.service.sbin`: Same as infnoise.service, binary path = /usr/sbin/
+- `infnoise.service.bin`: Same as infnoise.service, binary path = /usr/bin/ - uses config file from /etc/infnoise.conf
+- `infnoise.service.sbin`: Same as infnoise.service, binary path = /usr/sbin/ - uses config file from /etc/infnoise.conf
+- `infnoise.conf.systemd`: Config file for the systemd service, to set multiplier and serial number of device
 - `75-infnoise.rules`: udev rule to be used together with the systemd service
diff --git a/software/init_scripts/infnoise.conf.systemd b/software/init_scripts/infnoise.conf.systemd
new file mode 100644
index 0000000..80a5f3c
--- /dev/null
+++ b/software/init_scripts/infnoise.conf.systemd
@@ -0,0 +1,7 @@
+# systemd configuration file for the Infinite Noise TRNG
+
+INFNOISE_MULTIPLIER=1
+# keccak multiplier, default = 1
+
+INFNOISE_SERIAL=
+# serial number of device, default: ""
diff --git a/software/init_scripts/infnoise.service.bin b/software/init_scripts/infnoise.service.bin
index c915c80..8571e63 100644
--- a/software/init_scripts/infnoise.service.bin
+++ b/software/init_scripts/infnoise.service.bin
@@ -4,9 +4,10 @@ BindsTo=dev-infnoise.device
 After=dev-infnoise.device
 
 [Service]
+EnvironmentFile=/etc/infnoise.conf
 Type=forking
 WorkingDirectory=/tmp
-ExecStart=/usr/bin/infnoise --dev-random --daemon --pidfile /var/run/infnoise.pid
+ExecStart=/usr/bin/infnoise --dev-random --daemon --pidfile /var/run/infnoise.pid --multiplier ${INFNOISE_MULTIPLIER} --serial ${INFNOISE_SERIAL}
 User=root
 Group=root
 Restart=always
diff --git a/software/init_scripts/infnoise.service.sbin b/software/init_scripts/infnoise.service.sbin
index 9fbb8e0..ec660cf 100644
--- a/software/init_scripts/infnoise.service.sbin
+++ b/software/init_scripts/infnoise.service.sbin
@@ -4,9 +4,10 @@ BindsTo=dev-infnoise.device
 After=dev-infnoise.device
 
 [Service]
+EnvironmentFile=/etc/infnoise.conf
 Type=forking
 WorkingDirectory=/tmp
-ExecStart=/usr/sbin/infnoise --dev-random --daemon --pidfile /var/run/infnoise.pid
+ExecStart=/usr/sbin/infnoise --dev-random --daemon --pidfile /var/run/infnoise.pid --multiplier ${INFNOISE_MULTIPLIER} --serial ${INFNOISE_SERIAL}
 User=root
 Group=root
 Restart=always