• NTPD Refusing to accept time from GPSD

    One of the (minor) drawbacks of the Raspberry Pi is the lack of a hardware clock. Normally, you'd work around this by configuring a good pool of NTP servers to connect to. What do you do though, if you can't guarantee there will be an Internet connection available when needed?

    The solution is obvious, so obvious that many have already done it - use the time provided by a cheap GPS dongle. The gpsd daemon helpfully pushes the time to Shared Memory Segments (SHM) so it's a simple adjustment to the NTP configuration file to have NTPD pull the time from the dongle.

    Except, it seems on Raspbian, it isn't quite so simple. You've followed all the instructions (simple as they are) but are still seeing an entry like this

    # ntpq -p
         remote           refid      st t when poll reach   delay   offset  jitter
    ==============================================================================
    SHM(0)          .GPS.            0 l    -   16    0    0.000    0.000   0.001

    No matter what you try, reach stays at 0.

    Frustrating, and there's very little to give you a guide. This post will tell you what the issue is, as well as how to go about finding it should it re-occur

  • Usurping the BTHomeHub with a Raspberry Pi: Part 2 - DNS, DHCP and NTP

    In Part One, we configured our RaspberryPi to act as a Wireless access point and bridged the wireless and wired interfaces so that WLAN client's were easily accessible from the LAN.

    As part of that setup, we configured a DHCP server, however we haven't yet made it the DHCP server for the LAN - our tired old BTHomeHub is still the authoritative server for the network.

    In this part, we'll be reconfiguring our DHCP server so that it takes responsibility for the entire LAN, configuring DNS services, and making our Pi the LANs central NTP (Network Time Protocol) Server

    Step by step, we'll be configuring our Raspberry Pi to take over nearly all of the duties performed by the BTHomeHub.