These are the ramblings of Matthijs Kooijman, concerning the software he hacks on, hobbies he has and occasionally his personal life.
Most content on this site is licensed under the WTFPL, version 2 (details).
Questions? Praise? Blame? Feel free to contact me.
My old blog (pre-2006) is also still available.
See also my Mastodon page.
- Raspberry pi powerdown and powerup button (45)
- Repurposing the "Ecobutton" to skip spotify songs using Linux udev/hwdb key remapping (3)
- How to resize a cached LVM volume (with less work) (2)
- Reliable long-distance Arduino communication: RS485 & MODBUS? (6)
- USB, Thunderbolt, Displayport & docks (21)
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On a small embedded system, I wanted to run a simple Rails application and have it automatically start up at system boot. The system is running systemd, so a systemd service file seemed appropriate to start the rails service.
Normally, when you run the ruby-on-rails standalone server, it binds on port 3000. Binding on port 80 normally requires root (or a special capability enabled for all of ruby), but I don't want to run the rails server as root. AFAIU, normal deployments using something like Nginx to open port 80 and let it forward requests to the rails server, but I wanted a minimal setup, with just the rails server.
An elegant way to binding port 80 without running as root is to use systemd's socket activation feature. Using socket activation, systemd (running as root) opens up a network port before starting the daemon. It then starts the daemon, which inherits the open network socket file descriptor, with some environment variables to indicate this. Apart from allowing privileged ports without root, this has other advantages such as on-demand starting, easier parallel startup and seamless restarts and upgrades (none of which is really important for my usecase, but it is still nice :-p).