Raspbian 'stretch' - system build notes
 
 1. Copy os disk image to SD card.
 
 2. Mount the SD card to the host computer and navigate
    to the boot volume of the SD card.
 
 3. If using wired Ethernet, skip to step 6.
 
 4. Edit the wpa_supplicant.conf file with your wifi ssid and
    wifi password.
 
 5. Copy the wpa_supplicant.conf file to the root of the boot
    volume.
 
 6. Create an empty file named "ssh" in the root of the boot
    volume.
 
 7. Unmount the SD card and install in the Pi Zero.  Apply
    power and boot up the Pi Zero.
 
 8. Secure shell into the Pi Zero by running
        ssh pi@raspberrypi.local
    The password is 'raspberry'
 
 9. Configure the following by running
        sudo raspi-config
    In System Options modify the following
      hostname: nodepower
      password: YOUR_PASSWORD
    In Interface Options modify the following
      I2C: ON
    In Localisation Options modify the following     
      Locale: en_US.UTF-8 UTF-8
      Timezone: PACIFIC
      Keyboard: US
      WLAN: US
 
 10. If using wired Ethernet, disable wifi by adding the following
     line to the end of the /boot/config.txt file
       dtoverlay=disable-wifi
     This helps to conserve power.
 
 11. Disable Bluetooth by adding the following line to the end of
     the '/boot/config.txt' file:
       dtoverlay=disable-bt
     This helps to conserve power.
     [Optional] Run the once off command:
         sudo systemctl disable hciuart
 
 12. Set up ssh keys on client and import the public key
    to the Pi Zero .ssh directory.  Create .ssh directory
    on the Pi Zero.  In .ssh create a file authorized_keys
    and copy the public key to it.
 
 13. Backup and then modify /etc/ssh/sshd_config as follows
 
        #PermitRootLogin prohibit-password
        PermitRootLogin no
 
        #X11Forwarding yes
        X11Forwarding no
 
    Optionally turn off password authentication
 
        #PasswordAuthentication yes
        PasswordAuthentication no
 
 14. Setup tmpfs by backup and then modifying /etc/fstab.  Add
    the following lines to the bottom of the file.
 
        # uncomment if needed for web apps
        # These changes store all non-essential logs in ram to reduce
        # stress on the SD card due to frequent writes.
        tmpfs /tmp tmpfs nodev,nosuid,size=20M 0 0
        tmpfs /var/tmp tmpfs defaults,noatime,nosuid,size=20m 0 0
        tmpfs /var/log tmpfs defaults,noatime,nosuid,mode=0755,size=20m 0 0
        tmpfs /var/spool/mqueue tmpfs defaults,noatime,nosuid,mode=0700,gid=12,size=20m 0 0
 
 15. Reboot the Pi Zero by running
         sudo reboot
 
 16. Run updates by running the commands
         sudo apt-get update
    
     Optionally run all software updates
         sudo apt-get upgrade
         sudo reboot
 
 17. Install vim
       apt-get install vim
 
 18. Optionally copy pi backup archive from the ssh client to
     the /home/pi folder
         scp pi.zip pi@nodepower.local:~
 
 19. Restore files and directories from backup archive by running
       unzip pi.zip
     Use 'mv' to move folders and files to their appropriate locations.
 
 20. Make backups of /etc/rc.local, /etc/motd. Then, acting as superuser
     copy to /etc from the unzipped directory the files rc.local and motd.
 
 21. Install rrdtool
        sudo apt-get install rrdtool
 
 22. Install web server
 
     Apache2 
     ======
     sudo apt-get install apache2 -y
     sudo a2enmod rewrite
     sudo service apache2 restart
 
     PHP
     ===
     sudo apt-get install php libapache2-mod-php -y
     sudo service apache2 restart
 
 23. Acting as superuser, backup and then modify
     /etc/apache2/mods-available/userdir.conf
 
        # changed {date} by {name} to allow user .htacess file
        #AllowOverride FileInfo AuthConfig Limit Indexes
        AllowOverride All
 
 24. Enable user directories in apache2
        sudo a2enmod userdir
 
 25. Acting as superuser, backup and then modify
     /etc/apache2/sites-available/000-default.conf
 
        # changed 12-06-2019 by JLO to make user pi the html document root
        #DocumentRoot /var/www/html
        DocumentRoot /home/pi/public_html
 
 26. Acting as superuser, backup and then modify
     /etc/apache2/mods-available/php7.3.conf to allow user directories
     by commenting the lines at bottom of file.  E.g.,
 
        #<IfModule mod_userdir.c>
        #    <Directory /home/*/public_html>
        #        php_admin_flag engine Off
        #    </Directory>
        #</IfModule>
 
 27. Enable php in apache2
        sudo a2enmod php7.3
 
 28. Acting as superuser, backup and then modify /etc/apache2/envvars
     to create apache2 logs in tmpfs.  Add the following lines at the top
     of the file
 
        if [ ! -d /var/log/apache2 ]; then
          mkdir /var/log/apache2
        fi
 
 29. Acting as superuser, enable apache2 to access files the tmpfs /tmp
     directory by backing up and then modifying
     /lib/systemd/system/apache2.service
 
        # changed {date} by {name} to allow apache to follow symlinks
        # to the /tmp folder in tmpfs
        #PrivateTmp=true
        PrivateTmp=false
 
 30. Reload system deamons
        sudo systemctl daemon-reload
 
 31. Restart apache2 service
        sudo systemctl restart apache2
 
 32. Install i2c smbus python library by running
        sudo apt-get install python-smbus
 
 33. Reboot the Pi Zero by running 'sudo reboot'.
 
 34. Test all above modifications.