Any inbuilt way to change the hostname to the comitup-<nn> variable?

[revantjhalani]

If there are multiple comitup devices on the same network, there's bound to be hostname conflicts. Is there any inbuilt way to also change the hostname to the comitup- variable?

[davesteele]

if you are up to date, it is <nnn>. There is a .1% of 2 hosts having the same name. Also, look at the comitup.conf file.

[revantjhalani]

The conf only specifies how to add the hostname in the ssid, what I'd like to do is the opposite. I'd like to add the number as a suffix to the hostname. Also, I don't understand how the possibility of two devices having the same hostname is .1%? For instance, the prebuilt image you deliver has a default hostname of raspberrypi, if I were to flash 2 pis with that image and then connect them to the same network, won't there be a hostname problem right then

[davesteele]

True, but they also advertise on mdns as comitup-<nnn>.local.

There is automatic deconfliction with the "raspberrypi" name (on mdns). I have "raspberrypi" and "raspberrypi-2" on my network now. I've not looked into how that is managed.

This would be a decent addition to the Comitup Image. The package, though, should not be changing hostnames.

[davesteele]

The latest comitup image sets the hostname to the AP name on first boot.

[revantjhalani]

In the new image, I keep running across the error "unable to resolve host comitup-931: Name or service not known" while invoking any system commands. I haven't had a chance to look at the hosts and hostname files, I'll try to recreate the issue in a while, but thought that this could just be the behavior at the first system startup since you're now changing the hostname at runtime. Is that the case?

[davesteele]

I haven't seen this.

[minutmorph]

Hi David - first of all thank you for this project - it has become my starting point for every project recently! I have also been receiving this issue on the new image too (2021-03-17) - I am able to recreate it when running anything preceded with sudo.

eg. on first boot - my first action is to update the ap_name variable in /etc/comitup.conf (to "product-") and change the hostname to "device-$MACADDRESS" (for the exact reason mentioned above - to prevent conflict). Both actions require sudo, and doing this programmatically is difficult now on the new image. The line below gets the wlan0 mac address as a string and sets the hostname

# Change hostname to device-$MACADDRESS
pi@comitup-591:~ $ sudo hostname device-$(cat /sys/class/net/wlan0/address | sed -e 's/://g')
sudo: unable to resolve host comitup-591: Name or service not known

A quick google found me here: https://www.globo.tech/learning-center/sudo-unable-to-resolve-host-explained/

And the apparent solution is to include a loopback in /etc/hosts to the given hostname ie.

127.0.0.1             mynewhostname

I also found a way to change the /etc/hosts file programmatically - here's the full bash script below

#!/bin/bash

# Set Hostname
echo "Setting hostname..."
NEWHOSTNAME=$(cat /sys/class/net/wlan0/address | sed -e 's/://g')
sudo hostname device-$NEWHOSTNAME

# Add loopback to /etc/hosts file
echo "Adding loopback to /etc/hosts file..."
echo "127.0.0.1               device-$NEWHOSTNAME" | sudo tee -a /etc/hosts

Some notable strange behaviour that might be related:

1. When in AP mode - you can't even achieve changing the /etc/hosts file - sudo will not resolve, however, when connected to a host network, sudo has the same warnings but manages to update the file, seemingly fixing the problem!
2. The hostname always reverts back to the original session "comitup-" hostname - even if the new config specifies the ap_name to be device- and the hostname was changed before.
3. the ap_name variables such as and don't appear to work - I'm not sure if this is related or is a separate issue.... the AP simply displays as if and are strings rather than variables

I hope this helps.

Possibly related: Is there a way to force a new session variable programmatically? on every boot or trigger it on next boot perhaps... So a custom image can be provisioned knowing each device on first boot will not have the same initial session. This will also help with testing

[davesteele]

The persistent random number is stored in /var/lib/comitup/comitup.json. If it is set before comitup runs, it will not be overwritten.

The service that sets the host name runs exactly once, then self-deletes. In general, I don't want Comitup messing with hostnames.

The new ap_name variables currently require an "apt-get upgrade" to come alive.

[davesteele]

And the apparent solution is to include a loopback in /etc/hosts to the given hostname

A disk image with this change is uploading now.