dnsmasq configuration

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Debra Bennett
5 years ago
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1 Aim: Raspberry Pi searches for known router's (SSID) If the router is not found then it creates a hotspot so tablets, phones and computers can connect to the Raspberry Pi's WiFi hotspot, which is not routed to the internet but allows a connection via SSH, VNC etc. (Internet will not be available via Ethernet either while the hotspot is active but will be restored after a reboot and a known router is in range.) Requirements: Raspberry Pi 3, Raspberry Pi ZeroW or other Raspberry Pi with WiFi dongle* Internet Connection WiFi connection already set-up to your local router or any routers you are using with this script *some WiFi dongles don't work in adhoc mode or don't work with with the nl80211 driver used in this guide, so you may want to check this first before starting. Step1: To start with hostapd hotspot client and dnsmasq lightweight dns server need to be installed. Open a Terminal session. Update Raspbian with the latest updates by entering the commands: sudo apt-get update sudo apt-get upgrade To install hostapd enter the command: sudo apt-get install hostapd enter Y when prompted. To install dnsmasq enter the command: sudo apt-get install dnsmasq enter Y when prompted The installers will have set up the programme so they run when the pi is started. For this setup they only need to be started if the home router is not found. So automatic startup needs to be disabled. This is done with the following commands: sudo systemctl disable hostapd sudo systemctl disable dnsmasq Now the hostspot configuration file can be setup. This contains the name of the WiFi signal you will need to connect to (SSID) and the security password. To edit the configuration files I will be using the nano text editor but if you prefer an editor with an point and click interface then replace nano with leafpad in the following instructions. Hostapd Configuration Using a text editor edit the hostapd configuration file. This file won't exist at this stage so will be blank. sudo nano /etc/hostapd/hostapd.conf enter or paste the settings: interface=wlan0 driver=nl80211 ssid=rpi3hot hw_mode=g channel=6 wmm_enabled=0

2 macaddr_acl=0 auth_algs=1 ignore_broadcast_ssid=0 wpa=2 wpa_passphrase= wpa_key_mgmt=wpa-psk wpa_pairwise=tkip rsn_pairwise=ccmp The interface will be wlan0 The driver nl80211 works with the Raspberry Pi 3 onboard WiFi but you will need to check that your wifi dongle is compatable and can use Access Point mode. For more information on wifi dongles see elinux.org/rpi_usb_wi-fi_adapters The SSID is the name of the WiFi signal broadcast from the RPi, which you will connect to with your Tablet or phones WiFi settings. Channel can be set between 1 and 13. If you are having trouble connection because of to many wifi signals in your area are using channel 6 then try another channel. Wpa_passphrase is the password you will need to enter when you first connect a device to your Raspberry Pi's hotspot. This should be at least 8 characters and a bit more difficult to guess than my example. To save the config file press ctrl & o and to exit nano press Ctrl & x Now the defaults file needs to be updated to point to where the config file is stored. In terminal enter the command sudo nano /etc/default/hostapd Change: #DAEMON_CONF="" to DAEMON_CONF="/etc/hostapd/hostapd.conf" And save. dnsmasq configuration Next dnsmasq need to be configured to allow the PI to act as a router and issue IP addresses. sudo nano /etc/dnsmasq.conf Go to the bottom of the file and add the following lines #Pi3Hotspot Config #stop DNSmasq from using resolv.conf no-resolv #Interface to use interface=wlan0 bind-interfaces dhcp-range= , ,12h And then save (ctrl & o) and exit (ctrl & x) Step2: Now that hostapd and dnsmasq are configured we now need to make some changes to the interfaces file and then add a script that will detect if you are at home or not. Next we need to edit the interfaces file. There will be several entries already in the file. Look for references to Wlan0 and alter them as below.

3 Any reference to wpa_conf for wlan0 should be disabled by putting a # at the start of the line. Open the interfaces file with the command sudo nano /etc/network/interfaces edit the following lines as below auto lo wlan0 iface lo inet loopback allow-hotplug wlan0 iface wlan0 inet manual # wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf now save (ctrl & o) and exit (ctrl & x) Required only if: if your home routers SSID and password was listed in this file then the hotspot will probably not get generated. You will need to put a # infront of each line #iface wlan0 inet dhcp # wpa-ssid "myssid" # wpa-psk "Router Pasword" These details need to be in the wpa_supplicant.conf file to work with this setup. Add your router details to the wpa_supplicant.conf file with sudo nano /etc/wpa_supplicant/wpa_supplicant.conf and add the following commands to the bottom of the file. network={ ssid="myssid" psk="router Password" key_mgmt=wpa-psk } If in the future you change your router connection details with the WiFi icon by the clock then check that the changes have been made to the wpa_supplicant.conf file and not the /etc/network/interfaces file. Note: Change "myssid" to the ssid of your router and "Router Password" to the password of your router. Start-up Script The final stage is to setup the startup-scripts using the systemd process. if you have been updating Raspbian Jessie and not used a recent image you may not have some wifi tools installed. just chek you have iw installed with dpkg -s iw If it is not found then install it with sudo apt-get install iw This script will check what routers are available when the RPi. The first router found in the wifi settings will be connected to using existing configured WiFi settings. If no know routers are in range then a WiFi hotspot is created. Create the start-up script in a new file in /usr/bin/ sudo nano /usr/bin/autohotspot

4 Enter this script. (last modified 30th May 2017) #!/bin/bash #RaspberryConnect.com #Wifi config - if no prefered Wifi generate a hotspot #This two lines check for any SSIDs in your RPi's wifi settings wpassid=$(awk '/ssid="/{ print $0 }' /etc/wpa_supplicant/wpa_supplicant.conf awk -F'ssid=' '{ print $2 }' ORS=' ' sed 's/\"/''/g') ssids=($wpassid) #or check a restricted list of SSID,s that are setup. #Put a # infront of the two lines above first; #ssids=$(awk... & ssids=($wpassid) #Enter one or more ssids that are already setup in the wifi settings #Remove # below to use. separate SSIDs by a space, ('myssid1' 'myssid2') #ssids=('myssid1') #Main script createadhocnetwork() { ip link set dev wlan0 down ip a add /24 dev wlan0 ip link set dev wlan0 up systemctl start dnsmasq systemctl start hostapd } connected=false for ssid in "${ssids[@]}" do if iw dev wlan0 scan ap-force grep "$ssid" > /dev/null then wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf > /dev/null 2>&1 if dhclient -1 wlan0 then connected=true break else wpa_cli terminate break fi else echo "Not in range, WiFi with SSID:" $ssid fi done if! $connected; then createadhocnetwork fi One of the lines of the script may go off the right side of the webpage alternately this script is available to download here The line reads: ssids=$(awk '/ssid="/{ print $0 }' /etc/wpa_supplicant/wpa_supplicant.conf awk - F'ssid=' '{ print $2 }' ORS=' ' sed 's/\"/''/g') Thanks to Tino for this code

5 The line starting with ssids=$(awk... lists all routers in the Raspberry Pi's wifi settings. If you need to restrict this to only certain SSID's currently setup then put a # infront of the ssid=$(awk... line to deactivate it and also the line ssids=($wpassid). Then remove the # infront of #ssids=('myssid1') then in the line ssids=('myssid1') replace 'myssid1' with the SSID of your router. in the UK common SSIDs are in the format of SKY12345, BTHub-1234, TalkTalk12345, VM123456, plusnet1234 etc If you access other routers then enter them, with single quotes and a space between each entry. The script will try each one and make a connection to the first one that is available. Then save (ctrl & o) and exit (ctrl & x) make the autohotspot script executable with the command sudo chmod +x /usr/bin/autohotspot Next add a service file to systemd. Create a file in /etc/systemd/system and add the service file sudo nano /etc/systemd/system/autohotspot.service Enter the script [Unit] Description=Generates a non-internet Hotspot for ssh when a listed ssid is not in range. After=network-online.target [Service] Type=oneshot RemainAfterExit=yes ExecStart=/usr/bin/autohotspot [Install] WantedBy=multi-user.target Then save (ctrl & o) and exit (ctrl & x) This service file can be downloaded here now enable the Hotspot service with the command sudo systemctl enable autohotspot.service If you use a Hidden SSID... If your router does not broadcast the ssid the /usr/bin/autohotspot script will not find your router and always go to a hotspot. By scanning for your MAC address instead of your SSID the script will work. Your mac address will be printed on your router somewhere in the format XX:XX:XX:XX:XX:XX using letters and numbers. It can alternately by found using the command sudo iw wlan0 scan egrep "BSS SSID" Which will return all the routers in range, the top one should be your router. (My routers ssid is not hidden so you won't see the ssid but my results were as follows) BSS XX:XX:XX:XX:XX:XX(on wlan0) -- associated SSID: XXXXXXXX

6 BSS Load: where X is the address results. Once your know your MAC address the following changes can be made to the /usr/ bin/autohotspot script. Change: #enter required ssids: ssids=('ssid1' 'ssid2') ssids=('myssid1' 'myssid2') for #enter required MAC Addr: macadresses=('xx:xx:xx:xx:xx:xx' 'YY:YY:YY:YY:YY:YY') macadresses=('myroutermacadress') change: for ssid in "${ssids[@]}" do if iw dev wlan0 scan ap-force grep "$ssid" > /dev/null for for macadress in "${macadresses[@]}" do if iw dev wlan0 scan ap-force grep "$macadress" > /dev/null and change echo "Not in range, WiFi with SSID:" $ssid for echo "Not in range, WiFi with MAC:" $macadress The Router detection should now work for you. Thanks to Willem Me for supplying these modifications. Testing the Hostspot To test if the hotspot is being created edit the /usr/bin/autohotspot file again and change your SSID to something else such as myssid1off ssids=( 'myssid1' 'myssid2' ) to ssids=( 'myssid1off' 'myssid2off' ) Save the /usr/bin/autohotspot file and then reboot. When the desktop loads the WiFi network icon in the top right corner will be two screens instead of the usual WiFi icon. When the mouse is placed over the icon is should show a popup displaying the RPI3hot access point.

7 Check the WiFi signals in range with the wifi settings on a Laptop, tablet or Phone and you should see that one of them is RPI3hot Select RPI3hot as the WiFi signal to connect to. The security password will be the one you set in the hostapd.conf file. From my example that would be Now you are connected to the Raspberry Pi's hotspot and you can now open a SSH connection as usual using the IP address Once your happy it is all working, reset the SSID entry back to your routers SSID and your ready to go. This setup has been tested on a Raspberry Pi 2 and PiZero with a WiFi dongle and with a Raspberry Pi 3 and PiZero W all running Raspbian Jessie. Wifi and Hotspot Auto Switch Script I have an alternative script that can switch between wifi and a hotspot without rebooting using a timer or manually. Details are in this article Raspberry Pi - Auto WiFi Hotspot Switch Removal If you no longer require this script then it can easily be disabled without affecting your set-up. Restore your wifi startup by editing the /etc/network/interfaces file and removing the # from the line # wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf Then disable the startup script with the command sudo systemctl disable autohotspot After a reboot your RPI will connect to your router. Note: Dnsmasq bug: in versions below 2.77 there is a recent bug that may cause the hotspot not to start. This can be resolved by removing the dns-root-data. check your version with : dpkg -s dnsmasq versions 2.77 and above are ok. If not then try the command: sudo apt-get purge dns-root-data thanks to danny for highlighting this.

Raspberry Pi 3 Model B and JMRI with WiFi Access Point for Pi-SPROG One and Pi-SPROG Nano raspian-jessie build

Raspberry Pi 3 Model B and JMRI with WiFi Access Point for Pi-SPROG One and Pi-SPROG Nano 2017-04-10-raspian-jessie build June 2017 SPROG DCC These instructions describe the process of setting up a Raspberry