rover

README

rover

Dev environment setup

See Circle CI config for setup flow.

You also need protobuf compiler version 3 (at least). See https://github.com/golang/protobuf for instructions.

Forwarder setup

/etc/ssh/sshd_config

# Allow binding reverse tunnel ports to non-loopback interface.
GatewayPorts clientspecified
# Do not resolve SSH client IP address (can be slow).
UseDNS no
# Send keepalive packets to make sure the reverse tunnel ports are closed
# when connection is dropped.
ClientAliveInterval 15

Raspberry PI (A+ V1.1) setup

OS

Raspbian

configure WiFi via SD card

See Wireless CLI

raspi-config

In # raspi-config, use "Expand Filesystem" option to use the whole SD card. Right there as well, go to "Advanced Options" and enable "I2C", and agree to kernel module autoload.

save SD space and package installation time

See Documentation section of Reducing Disk Footprint

/boot/config.txt

• set GPU mem allocation to 128MB (required for camera): gpu_mem=128
• Enable i2c: dtparam=i2c_arm=on
• Enable audio: dtparam=audio=on
• Enable camera: start_x=1
• Disable camera LED: disable_camera_led=1

/boot/cmdline.txt

• Remove a console= reference to serial0 (this is a UART interface) to allow normal SIM800 module interactions

hostname

# hostname rover.dasfoo.org

Also update /etc/hostname and /etc/hosts.

packages

# apt install pptp-linux

systemd

• Do not use UART as console: systemctl disable serial-getty@ttyAMA0.service

• Add services:

  # ln -sf /home/pi/rover/systemd/<svc>.service \
    /etc/systemd/system/multi-user.target.wants/<svc@optional_args>.service`
  

  • reverse tunnel for ssh: reverse-tunnel@<remote_host>:22.service. Make sure ssh <remote_host> works (doesn't ask for host key / password)

  • autoswitch sim800 and wlan0: autoswitch-wlan-sim800@<isp>.service.

  • rover API server: rover.service

  • reverse tunnel for ssh and rover API server: reverse-tunnel@<remote_host>.service and its config. Each config line consists of 2 numbers: a remote port and a local port. A port is bound to "localhost" interface by default; a colon (":") prefix will bind it to all interfaces, making it accessible externally. Example:

    $ cat $HOME/.config/reverse-tunnel/<remote_host>
    <internal_only_remote_port_for_ssh> 22
    :<external_remote_port_for_rover_API> <local_rover_API_port>
    

/etc/fstab

Mount /tmp as tmpfs (RAM):

tmpfs /tmp tmpfs defaults,noatime,nosuid,size=50m 0 0

groups

Optional, as systemd runs the script as root now.

pi must be a member of dip group to call for pon/poff:

# usermod -aG dip pi

ppp

Replace $ISPNAME with what's your ISP suggests as "endpoint", e.g.: data.umts.example.org

$ cat /etc/ppp/peers/$ISPNAME
# serial path
/dev/ttyAMA0
# baud rate
115200
connect '/usr/sbin/chat -v -f /etc/chatscripts/gprs -T $ISPNAME'

# do not require auth from remote side
noauth
# add default route
defaultroute
# even if there's already default route, replace it with PPP
replacedefaultroute
# ask the peer for up to 2 DNS servers
usepeerdns
# name the interface pppN, N=0
unit 0
# dial again when connection is lost
persist
# rechallenge the peer every 321 seconds
chap-interval 321
# random string to identify connection
ipparam $ISPNAME
# send echo every 20 seconds
lcp-echo-interval 20
# reconnect if not responded to 3 echoes in a row
lcp-echo-failure 3
# do not try to guess own IP address (only receive it from ISP)
noipdefault
# do not try to guess remote peer IP address (only receive it from ISP)
noremoteip
# detach from controlling terminal only once connection is established
updetach

# (optionally) disable compression
#nopcomp
#novjccomp
#nobsdcomp
#nodeflate
#noaccomp

To test: power on SIM800 and # pon $ISPNAME.

sshd

It might be useful to add PasswordAuthentication no to your /etc/ssh/sshd_config if logging in to Pi with a key.

Removing password from pi user might make debugging network issues (by plugging in a keyboard) a bit harder.

application

Generate a key for a service account at Cloud IAM. You can use "Compute Engine default service account", or create a new one. The JSON file downloaded should be placed in $HOME/.config/gcloud/application_default_credentials.json.

backup

Once everything is configured, power Pi off (# poweroff) and unplug the SD card. Then plug it into your computer, find out dev node for it (e.g. /dev/mmcblk0 or /dev/rdisk2) and make a backup:

# dd if=/dev/rdisk2 of=rover_backup.img bs=1m