doc(loc/README): Show how to disable swap file

[EVA-2020-02.git] / doc / location / README.org

diff --git a/doc/location/README.org b/doc/location/README.org
index 7158a730f0955c7fd8b9dd7e30da9156d47f784f..397968f9e2a3de5ba0bf7d525fbe8e2cce9d7029 100644 (file)
--- a/doc/location/README.org
+++ b/doc/location/README.org
@@ -1,10 +1,9 @@
 * Location Logging
 This document was created by Steven Baltakatei Sandoval on
-<2020-06-29 Mon 12:14> under a [[https://creativecommons.org/licenses/by-sa/4.0/][Creative Commons BY-SA 4.0 license]]. It
-was updated by Steven Baltakatei Sandoval on <2020-06-29 Mon 22:06>.
+~2020-06-29T12:14Z~ under a [[https://creativecommons.org/licenses/by-sa/4.0/][Creative Commons BY-SA 4.0 license]]. It
+was updated by Steven Baltakatei Sandoval on ~2020-06-30T19:44Z~
 #+TITLE: Ninfacyzga-01 Manual
 #+AUTHOR: Steven Baltakatei Sandoval
-#+DATE: 2020-06-29T22:16Z
 #+EMAIL: baltakatei@gmail.com
 ** Narrative
 Ninfacyzga-01 records (logs) its position in time and space using a
@@ -112,7 +111,6 @@ conflict so a simple stacking and soldering with long header pins is
 possible.
 
 **** Software Setup
-
 ***** Install Executables
 
 Install Raspbian 10 Buster onto an SD card image. See the Raspberry Pi
@@ -132,6 +130,45 @@ Install ~syncthing~ for log file transfer capability.
 Place ~age~ binary (the one compiled for ARM CPU architecture for
 Linux) in ~$HOME/.local/bin~.
 
+***** Disable Swap File
+Since standard Raspbian 10 (Buster) install involves copying
+unencrypted file system image to SD card which is mounted by the
+Raspberry Pi, system memory may be written to disk in the form of a
+Swap file as described [[https://ideaheap.com/2013/07/stopping-sd-card-corruption-on-a-raspberry-pi/][here]]. In order to reduce the chance that
+location log data is ever written to disk, swap file functionality
+must be disabled[fn:ideaheap_20130731_disableswap].
+
+Raspbian 10 uses dphys-swapfile to manage a swap file. It may be
+disabled persistently[fn:rpf_20190702_disableswappersist] by running
+the following command:
+
+: sudo systemctl disable dphys-swapfile.service
+
+To view the status of the swap file in Raspbian 10, run ~free -m~:
+
+#+BEGIN_EXAMPLE
+pi@ninfacyzga-01:~$ free -m
+          total    used    free  shared  buff/cache   available
+Mem:        432      86      36      21         309         268
+Swap:        99       0      99
+#+END_EXAMPLE
+
+After disabling the swap file and rebooting:
+
+#+BEGIN_EXAMPLE
+pi@ninfacyzga-01:~$ free -m
+          total    used    free  shared  buff/cache   available
+Mem:        432      89     214       3         128         289
+Swap:         0       0       0
+#+END_EXAMPLE
+
+[fn:ideaheap_20130731_disableswap] Explanation:
+https://ideaheap.com/2013/07/stopping-sd-card-corruption-on-a-raspberry-pi/
+
+[fn:rpf_20190702_disableswappersist] Persistant disabling of swap in
+Raspbian 10 Buster:
+https://www.raspberrypi.org/forums/viewtopic.php?p=1490692&sid=5c596a124b7805d6b10dab8d3d7caf16#p1490692
+
 ***** Automatic Start Configuration
 
 Edit the user cron job list with ~$ crontab -e~ to add the following
@@ -186,7 +223,7 @@ An ~age~ encryption key may be generated like so:
 #+BEGIN_EXAMPLE
 $ umask          # Gets current umask
 0022             # Note: This is the default umask for Raspbian 10
-$ umask 066      # Sets umask so key.txt will have no permissions except for owner (you)
+$ umask 066      # So key.txt will have no perms except for owner (you)
 $ umask          # Confirm umask set to 066
 0066
 $ age-keygen > key.txt