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Has anyone a working solution to bring up eth0/wlan0 when they are down using the information in interfaces.d/wlan0 and interfaces.d/eth0?

I would need it for an IoT device that might have an available ifconfig for eth0 or for both and ifconfig eth0 and wlan0.

I would also like the device to connect if the cabled/wifi is available some time after the device was powered.

I would need my device to reconnect whenever:

  • the connection of the router drops temporarily
  • the ethernet cable gets unplugged/replugged
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  • Do you really need ifupdown to manage networking? It isn't default on latest Raspbian. On Raspbian Stretch there is dhcpcd used by default and both interfaces wlan0 and eth0 reconnect out of the box. – Ingo Apr 8 '19 at 20:00
  • I know that. My colleague removed it because it says the ifupdown was better. is dhcpcd actually better? – Francesco Meli Apr 8 '19 at 20:05
  • I know very little about it so I need to trust who knows better. – Francesco Meli Apr 8 '19 at 20:06
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If you do not need ifupdown you can use the official supported Raspbian Stretch distribution. Just flash it to a SD Card, configure wpa_supplicant for wifi and everything works out of the box. If you plug in an ethernet cable the RasPi will get connected. It will also do it again if plug it out and in.

The same with WiFi. Once configured the RasPi connects to the hotspot. If the hotspot gets down or the RasPi leaves its range the connection will drop of course. But it comes again when going back into the range or when the hotspot gets up.

By default dhcpcd is working as network system. The Raspberry Pi Foundation means it is better than ifupdown. I mean systemd-networkd is better and it seems that ifupdown becomes deprecated. My suggestion is to use either default dhcpcd or for more sophisticated use cases systemd-networkd.

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  • ifupdown2 is actually quite nice and pretty popular in ISP infrastructure and datacenters. – mniess Apr 9 '19 at 1:12
  • @mniess Anyway, it's not available on the Raspbian repository. – Ingo Apr 9 '19 at 9:24
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If using raspberry pi 3+ be aware that the driver has a bug explained here may give issues to correctly manage eth0 and wlan0: https://github.com/raspberrypi/firmware/issues/1100

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