Add notes on how to move apt cache to tmpfs (ram)

docs/README.md

@@ -21,6 +21,7 @@ Items marked ```REQUIRED``` are assumed to be setup and working. You've been war
 * [System Monitoring (REQUIRED)](monit.md)
 * [CPU Governor (VERY SMART)](cpu_governor.md)
 * [Logs in RAM (log2ram / VERY SMART)](log2ram.md)
+* [Apt use RAM (VERY SMART FOR 4Gb RAM)](apt_cache_tmpfs.md)
 * [Pimoroni Fan Shim](pimoroni_fan_shim.md)
 * [HDMI Scheduled On/Off](scheduled_display.md)
 * [Backups via restic](restic.md)

docs/apt_cache_tmpfs.md

@@ -0,0 +1,18 @@
+# tmpfs apt cache
+
+**Please Note: this will use 512M RAM for the tmpfs (it'll usually be smaller) and can cause apt automatic updates to fail. You'll need/want to watch your logs and automatic updates if using this setup.**
+
+The below commands will enable tmpfs (in memory filesystem) for ```/var/cache/apt``` which has heavy disk write turnover due to automatic updates.
+
+``` sh
+
+sudo -sHu root
+rm -r /var/cache/apt/*
+cat >> /etc/fstab <<EOF
+tmpfs /var/cache/apt tmpfs size=512M,defaults,noatime,nodiratime 0 1
+EOF
+
+mount /var/cache/apt
+df -h /var/cache/apt
+
+```