Chapters about optimising boot time and about read-only

I added a chapter about disabling unnecessary services in order to decrease boot-time. And I added a short tip about read-only mode.

diff --git a/CAR INSTALL.md b/CAR INSTALL.md
index 062b6df5242c9a615093650e014471823a13235c..b24c86c7088550a3f38ce54f68fac040d3581ea8 100644 (file)
--- a/CAR INSTALL.md
+++ b/CAR INSTALL.md
@@ -193,6 +193,24 @@ denyinterfaces wlan0
 ```
 From this point on, at least on the Raspberry Pi, if you reboot the machine, it will not reconnect to your network – instead, it will act as the WiFi base station you have configured with `hostapd` and `isc-dhcp-server`.
 
+### Optimise startup time
+
+There are quite a few services that are not necessary for this setup. Disabling them can increase startup time. Running these commands disables them:
+
+````
+sudo systemctl disable systemd-timesyncd.service
+sudo systemctl disable keyboard-setup.service
+sudo systemctl disable triggerhappy.service
+sudo systemctl disable dhcpcd.service
+sudo systemctl disable wpa_supplicant.service
+sudo systemctl disable dphys-swapfile.service
+sudo systemctl disable networking.service
+````
+
+### Read-only mode
+
+Run `sudo raspi-config` and then choose `Performance Options` > `Overlay Filesystem` and choose to enable the overlay filesystem, and to set the boot partition to be write-protected. 
+
 ### Ready
 Install the Raspberry Pi in your car. It should be powered from a source that is switched off when you leave the car, otherwise the slight current drain will eventually flatten the car's battery.