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Comment by willis936 | Hacker News Reader

I have redundant pi holes and NTP servers running. One of them is GPS/PPS trained with chrony for some truly accurate network time.

I have another pi with a SCART hat and 180 GB of ROMs driving my BVM.

I have a 0w modulating its clock with Daftendirekt at 7am every morning for a pirate FM radio alarm clock.

If I had more impulse purchasing power I’m sure I would like to experiment with octoprint on my CR10S-Pro.

There are lots of things you can do with Pis. My use cases are far from the most fun or clever. You just have match them to your interests :)

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To be fair, I have 7 Pis running on my network. Home Assistant, 2x Pi-Holes (for redundancy), 1 magic mirror, my Weasleyclock, 1x w/ a hi-fi berry acting as a Spotify streaming device, and a garage door sensor. So roughly half the pis are in service. Maybe only 5% of all the sensors and projects are.

How do you set up the pi holes for redundancy? Just manually configured as primary and secondary DNS, or some nifty configuration syncing?

My guess would be for guest/home use or maybe for different devices/profiles.

The typical reason for running redundant pi holes is high availability. If you really want all DNS traffic to go through your filter then your internet ceases working as long as your DNS server stops running.

Both. Have your router (optionally all clients) point to each DNS server. You can go further by keeping the pi holes synchronized:

https://github.com/vmstan/gravity-sync

Since some hostile clients (such as TVs) have hard coded DNS, it is necessary to forward all port 53 and 853 traffic to a pi hole. This is easy enough with NAT redirection rules in the router, even with two pis.

https://www.myhelpfulguides.com/2018/07/30/redirect-hard-cod...

Not your parent poster, but I manually configured them as primary and secondary DNS servers (dockerized PiHole), and then just used pi-hole's "export configuration / restore configuration" tool to keep the DNSs mostly in sync.

I heard there's a tool called Gravity Sync that will sync them, but I have not tried it yet.

Techno Tim on the topic https://www.youtube.com/watch?v=IFVYe3riDRA

https://github.com/vmstan/gravity-sync

I just advertise both Pi-Holes via DHCP and when I configure manual DNS settings. The primary DNS gets the vast majority of the DNS traffic, about 150 requests/minute and the secondary gets about 10 requests/minute (mostly from a single device).

Both piholes are on different UPS power, different switches, in different locations. In theory the lights will go out on the main UPS and switch first (it draws more power), but this configuration did save me once.

I have a rpi 2b with a hifi berry DAC hat too. It works great. It is attached to a timecapsule with 20cm ethernet and usb cables, for data, network and power. Nothing important on the sd card.

If you have an extra Pi Zero W, Klipper has lower system requirements than Octoprint and runs better if you don't need any of the plugins that Octoprint offers, or a USB webcam hooked up.

Though it will involve flashing Klipper over Marlin on the CR10. That just means more stuff to tinker with!

Daftendirekt - the Daft Punk track? By "modulating its clock" do you mean playing the song as an alarm?

Sorry, I meant "Homework" as in the entire album.

By "modulating the clock" I mean modulating the SoC base clock frequency (nominally 100 MHz, but increased to be a valid and unused FM channel, if decreased then the pi locks up) with the audio to make an FM transmitter. Hook up a wire to the clock output GPIO pin and you have an FM antenna. Lay it next to an old FM clock radio and you now have a clock radio that plays whatever you want. Make a cron job and forget it.

https://github.com/pimylifeup/fm_transmitter

That is pretty cool. I'm actually working on a Raspberry Pi based clock and now I want to incorporate this somehow. Thanks for sharing.

I’m certain it plays hell on software timekeeping. If you don’t have an RTC then switching to chrony and increasing the poll rate should help prevent potential clock error.

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