doc(bkgpslog):Add note to simplify main loop

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

diff --git a/doc/location/README.org b/doc/location/README.org
index 50a0b5ed5d0e7f449a8d3746abed31f4a148edbd..397968f9e2a3de5ba0bf7d525fbe8e2cce9d7029 100644 (file)
--- a/doc/location/README.org
+++ b/doc/location/README.org
@@ -1,7 +1,10 @@
 * 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
+#+EMAIL: baltakatei@gmail.com
 ** Narrative
 Ninfacyzga-01 records (logs) its position in time and space using a
 [[https://en.wikipedia.org/wiki/Satellite_navigation_device][GPS receiver]]. The NMEA location data produced by the receiver is
@@ -72,7 +75,7 @@ An ~ssh-rsa~ or ~ssh-ed25519~ SSH public key string may be used instead of
 the bech32 public key string produced by ~age-keygen~ for convenience.
 
 Help information for ~age~ is available by running ~$ age --help~.
-***** Encryption
+***** Encryption Commands
 Files may be encrypted to several recipients using a command similar to:
 #+BEGIN_EXAMPLE
 timeout "60s" gpspipe -r | gpsbabel -i nmea -f - -o gpx -F | age \
@@ -86,7 +89,7 @@ In this example, the strings beginning with ~age1...~ are
 bech32-formatted public key strings. 
 
 
-***** Decryption
+***** Decryption Commands
 Files may be decrypted using a command similar to:
 
 #+BEGIN_EXAMPLE
@@ -108,7 +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
@@ -128,6 +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
@@ -156,8 +197,8 @@ may resemble:
 @reboot /bin/bash ~/bkgpslog -c -e -r age1z2...qkv6p -o ~/dir
 #+END_EXAMPLE
 
-The ~age1z2...qkv6p~ is an ~age~ public key string. See the Encryption
-Methods section for an explanation.
+The ~age1z2...qkv6p~ is an ~age~ public key string. Please see the
+[[*Key Generation][Key Generation]] section for an explanation.
 
 The options are:
 
@@ -182,7 +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