Re-connecting Wi-Fi

· 2 min read · December 27, 2025 · #tech #linux #nixos #config

Having gone home to visit my parents for Christmas, I am pleasantly surprised to find that their village has finally acquired fibre broadband. As it’s always been a mobile signal blackspot—typically I find it hovers somewhere between No signal and E, occasionally claiming 3G or 4G, although I am told that most of those indicators are a lie—it is nice to have >100Mb/s and, above all, a stable connection.

One unintended, if easy to fix, side effect is that their Wi-Fi access point changed. The SSID was ported over but the old passphrase was insufficiently long for the new model so it had to change. After about a minute of wondering why I couldn’t connect, I realized what was going on and fired up nmtui to change the passphrase.¹^,² Unfortunately the colour scheme for the Modify connection page was illegible to me. So I finally read the man pages for nmcli to do it from the command line.

Herewith the crib in case anyone else other than future-me will find it useful. No need for sudo in my case as I’m in the networkmanager group.

# set the passphrase for existing wireless network ("connection") NAME to PASSPHRASE
nmcli connection modify 'NAME' wifi-sec.psk 'PASSPHRASE'

# create a new connection NAME on SSID with PASSPHRASE
nmcli connection add type wifi \
      con-name 'NAME' \
      ssid 'SSID' \
      802-11-wireless-security.key-mgmt wpa-psk  \
      wifi-sec.psk 'PASSPHRASE'

# change to the network NAME you just created
nmcli connection up 'NAME'

And to add the 2.4GHz specific Wi-Fi network that was created to support the new solar panel inverter installation because the inverter is too far away in signal terms from the access point for 5GHz to reach. ↩
And, of course, once my dad had remembered that it had indeed changed and furthermore, what the new one was. ↩