Finally getting down to assembling and installing this 7 node cluster.
Tag Archives: raspberry pi
I got Fedora 32 installed on an RPi 4 8GB, booting off USB, with UEFI and ACPI. I followed Robert Grimm’s instructions here, and had an additional set of complications summarised here. There’s not much to say except that it was fiendishly complicated. But it works beautifully now, and is reasonably quick too especially when you consider how little it cost.
So let’s talk about costs (all include tax and delivery):
|Raspberry Pi 4 8GB||£77.33|
|SanDisk 500GB SSD x 2||£149.98|
|small SD card needed for booting||£free|
Only one of the SSDs is actually used, but if you follow Robert’s instructions you will need two. I didn’t have any external USB SSDs that were both USB 3 and not spinning hard disks, so I had to buy these, but I’ll be able to reuse one in a future project. The SD card is required to work around a bug in the UEFI firmware, but I happened to have one lying around.
It took me about an hour to work out that I had the board plugged in the wrong way around, and that’s why nothing worked. My excuse is we’re in the middle of a heatwave at the moment ….
Anyway, the picture above is how you’re supposed to do it.
The board almost immediately finds a timepulse.
After running for a little while:
# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== xPPS(0) .PPS. 0 l 13 16 377 0.000 -7.334 0.159 xipv6test.te.net 188.8.131.52 3 u 51 64 377 72.959 -1.776 0.711
(and yes I know it says Stratum 0 …)
The output is saying that the GPS source (PPS) has an offset of 7.3ms from the internal clock. The stratum 3 internet source is 1.8ms from the internal clock (but note the internal clock is likely wrong). The delay (round trip?) to the local clock is 0, and the delay from the internet source is 73ms.
They are both currently marked as “x” meaning “falsetickers”. I think ntpd needs a bit longer to decide to use the GPS source.
# ntpq -c rv associd=0 status=0018 leap_none, sync_unspec, 1 event, no_sys_peer, version="ntpd firstname.lastname@example.org Sat Jul 4 15:08:48 UTC 2015 (1)", processor="armv7l", system="Linux/3.18.11-v7+", leap=00, stratum=1, precision=-20, rootdelay=0.000, rootdisp=86.994, refid=PPS, reftime=d942771e.6dc41fc9 Sat, Jul 4 2015 16:15:42.428, clock=d9427c3a.d8cd27b8 Sat, Jul 4 2015 16:37:30.846, peer=0, tc=4, mintc=3, offset=0.003, frequency=0.000, sys_jitter=0.116, clk_jitter=3.476, clk_wander=0.000
Update: After reading this Red Hat article and this ntp.org document, I realized my mistake was having only two clocksources, which is the worst configuration for ntpd. Adding a bunch more sources makes it better:
# ntpq -c peers remote refid st t when poll reach delay offset jitter ============================================================================== oPPS(0) .PPS. 0 l 16 16 377 0.000 -0.094 0.008 *server.104media 184.108.40.206 2 u 30 64 377 29.748 3.890 0.610 -ns2.vnet.sk 220.127.116.11 3 u 29 64 377 50.536 0.622 0.268 +nero.grnet.gr .GPS. 1 u 27 64 377 71.089 4.371 0.619 -frankfurt1.firs 18.104.22.168 3 u 26 64 377 35.655 5.620 0.541 -time.rdg.uk.as4 22.214.171.124 3 u 40 64 377 19.761 3.070 0.197 -ntp1.ic.net.uk 126.96.36.199 2 u 43 64 377 18.153 3.659 0.176 -ns0.luns.net.uk 188.8.131.52 2 u 48 64 377 25.761 3.648 0.219 +ntppub.le.ac.uk 184.108.40.206 2 u 47 64 377 21.566 3.783 0.520
However for some reason it only works when I restart the NTP server a minute after boot. It may be that the kernel PPS device isn’t ready when the NTP server starts first time. In any case, I added this to
( sleep 60 ; service ntp restart ) &
I’m following the instructions here and here to try and make a Stratum-1 NTP server using GPS and a Raspberry Pi 2. If this works, I should have a very accurate NTP server for a very reasonable amount of money.
I ordered the Raspberry Pi 2 from Amazon, and the other parts from HAB Supplies in the UK. The total cost (prices include tax) was:
|Raspberry Pi 2||£29.99|
|GPS expansion board||£35.99|
|Antenna and cable||£41.99|
Edit: I already had a spare 32GB SD card and power supply. If you don’t have those already, you’d need to buy them too.