Blog of spblinux

Mathematica comes preinstalled on raspbian and is free for personal use. Adding a vnc or rdp server to a raspberry pi running raspbian allows to display and control Mathematica with an iPad. If the raspberry pi is configured as wlan access point you get a free and rather mobile installation of Mathematica.

Required hardware: raspberry pi model B, 16 GB sd(hc) card (at least 4 GB), ew-7811un wireless usb adapter; device running a vnc or rdp  viewer (e.g. iPad with RD Client app).

1. Installation of raspbian to sd card:
   download raspbian image http://downloads.raspberrypi.org/raspbian_latest
   unzip the file
   copy it to the sd card (linux: dd if=your_file of=/dev/sdX bs=1M; sdX is the device name of the sd card)
2. Configuration of raspbian on raspberry pi:
   for the first run plug monitor, keyboard, lan and usb current source into raspberry pi;
   raspi-config gets started automatically on first boot
   resize raspbian partition to full size of sd card (using the menu of raspi-config)
   set hostname, keyboard, language, timezone, password; enable ssh server; boot into console
   login as user pi and become root with sudo su. Run apt-get update and then apt-get upgrade
3. Add software to raspbian (as root user)
   apt-get install mc (I cannot live without)
   apt-get install xrdp
   apt-get install tightvnc-server
   apt-get install hostapd dnsmasq
4.  The xrdp server works with the default configuration. Alternatively use tightvnc-server as described here:
   with  VNC_USER=”pi”, HOME=”/home/pi”,FOO_ID=1
   and set as user pi a password for vnc with vncpasswd;
   after reboot the vnc server will listen on port 5901
5. Configure the wlan router function as described here, but make the following changes:
   the program /usr/bin/hostapd installed by raspian has to be replaced by  a self compiled version (mine is here – having used these instructions); (or you might use this file mentioned in this note)
   add dns server 8.8.8.8 to /etc/dnsmasq.conf: dhcp-option=6,8.8.8.8
   (ios clients seem to be picky about non standard network masks. So configure wlan0 with 255.0.0.0 and adapt dnsmasq.conf.
   dhcp-range=interface:wlan0,10.0.0.2,10.0.0.20,10.254.254.20,255.0.0.0,infinite)
   add modules to /etc/modules (one per line):
   nf-conntrack-ipv4 iptable-nat ipt-MASQUERADE (optional iptable-filter )
   do not create the file /etc/network/ifup.d/router.sh, but add the 2 lines of this file to /etc/rc.local
   ifup wlan0
   iptables –table nat -A POSTROUTING –out-interface eth0 -j MASQUERADE
   #optional: iptables -A FORWARD –in-interface wlan0 -j ACCEPT
   #optional: iptables -I INPUT -i wlan0 -p udp –dport 67:68 –sport 67:68 -j ACCEPT
   (and make sure that the newly added lines are above the line “exit 0”)
   Remark: long iptables options have — which tends to get displayed as unicode long hyphen; (has to be replaced manually when using copy and paste):
   To test hostapd and/or dnsmasq run it on the console: hostapd /etc/hostapd/hostapd.conf
   and/or dnsmasq -u dnsmasq –conf-file=/etc/dnsmasq.conf -d
6. Plug the mini wlan adapter ew-7811un into the raspberry pi and reboot
   try to join wlan Himmbeerhacks and try to connect with rdp to 10.0.0.1 or open 10.0.0.1:5901 with a vnc viewer (like  RD Client or Remoter VNC on iPad).

Further trial and error shows that with a bluetooth keyboard rdp works better than vnc. Especially square brackets (alt+5, alt+6) do not work well with vnc – at least in my setup with locale swiss german. That is why I started to use xrdp and the free microsoft remote desktop client for iOS.