Of minor note, should others have a similar issue: it now takes a bit longer than before when logging in to connect to the network. I get a spinning cursor for about 15secs on logon (to xfce desktop) as it is detecting and connecting to the network. I'm sure that's longer than on Beowulf. So if I'm really speedy launching email / browser then it won't have acquired the connection. But I'm not complaining, just noting.

Thanks again, such a brilliant and helpful forum.

For a laptop, you might want a slightly more flexible configuration, and to use the wpa_gui to deal with new wireless access points.

First, enter the following at the top of /etc/wpa_supplicant/wpa_supplicant.conf:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
p2p_disabled=1

Secondly, bring down wlan0 (ifdown wlan0) before changing /etc/network/interfaces to have the follwing variant declaration:

auto wlan0
iface wlan0 inet manual
         wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

iface default inet dhcp

You'll note the difference of having a manual stanza with wpa-roam rather than wpa-conf, and a seemingly extra stanza declaring use of a dhcp configuration for a virtual default interface. All that is in support of roaming with dhcp.

Next, install wpagui (that's the package name for the wpa_gui tool) as user management tool for connecting your wireless interface to available acccess point by choice. By virtue of the update_config=1 setting you may save accesspoint settings so wpa_supplicant can find them "automatically" later.

You might also need to re-login the user after ensuring the user is in the netdev group, as per that first configuration line which wpa_supplicant will use for its control sockets.

With that you should be all set. for completeness, the p2p_disabled=1 is needed in order to disable that function which otherwise causes wpa_supplicant to be confused.. I'm not sure about the details.

by startup do you mean a reboot of the machine?

Yes, when I turn on or reboot the machine I don't get the automatic connection to the wireless network that I used to. (This is at home so there's a persistent wireless network waiting for it.)

And thanks for suggesting. Always worth trying in case it made the difference.

Its just another way to connect wpa_supplicant using a conf file. Thought it might help.

You can manually connect using ifup wlan0 ?

Yes, manual connection is fine.

Unfortunately no difference. No automatic connection on startup but manual forcing works fine. Out of interest, does this change how it connects or is the 'wpa_supplicant' line a convenient shorthand for what I previously had in /etc/network/interfaces?

# apt install rfkill

then let us know the output of using sudo or root account

# rfkill list 

sorry i didnt read your post correctly.

You can manually connect using ifup wlan0 ?

so maybe reset the network interfaces file like so.

# wpa_passphrase ESSID WPAKEY > /etc/wpa_supplicant/wpa_supplicant.conf

then edit /etc/network/interfaces file to look like so.

auto lo
iface lo inet loopback

auto wlan0
iface wlan0 inet dhcp
         wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

My /etc/network/interfaces is:

auto lo
iface lo inet loopback

#allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
   wpa-ssid {my-ssid}
   wpa-psk {passphrase}

I've tried alternating 'allow-hotplug' and 'auto'. Neither triggers automatic connection, but both work when I manually force it using:

ip link set wlan0 up
service networking restart

How do I make the connection automatic and persistent at startup/logon, please?