diff --git a/update b/update
index a9188a67..3ae8add9 100755
--- a/update
+++ b/update
@@ -105,6 +105,22 @@ else
   FLAG=1
 fi
 
+FILE=/etc/systemd/system/pacsatsim.service
+if [ -f "$FILE" ]; then
+  if [[ $(diff systemd/pacsatsim.service /etc/systemd/system/pacsatsim.service) ]]; then
+    echo "changed command.service."
+    sudo cp /home/pi/CubeSatSim/systemd/pacsatsim.service /etc/systemd/system/pacsatsim.service
+    FLAG=1
+  else
+    echo "no change to pacsatsim.service."
+  fi
+else
+  echo "creating pacsatsim.service."
+  sudo cp /home/pi/CubeSatSim/systemd/pacsatsim.service /etc/systemd/system/pacsatsim.service
+  sudo systemctl enable pacsatsim
+  FLAG=1
+fi
+
 FILE=/home/pi/CubeSatSim/sstv_image_1_320_x_256.jpg
 if [ ! -f "$FILE" ]; then
     echo "Copying SSTV image 1."