Adding ad-hoc Wifi without breaking existing ethernet.. no bridge or routing

I went back to trying to set up the receiving device as an access point.

The problems I was having was that the SSID and passphrase I used were too short; there is an 8-character minimum.

Attempting to start hostapd would say it failed, and journalctl -xe would report "failed to start advanced ieee 802.11 ap and ieee 802.1x/wpa/wpa2/eap authenticator".

Because I'm using fixed IP addresses for each device I was looking for the most simple configuration, and not using ip routing or bridging.

The configuration changes required to make this work follows:

Added two lines to /etc/dhcpcd.conf:

static ip_address=192.168.XX.YYY/24

(note that XX.YYY should be replaced with your choice)

Next, I added these two lines to /etc/dbsmasq.conf:

dhcp-range=192.168.XX.1,192.168.XX.20,255.255.255.0,24h

(Again, XX represents your choice, as should the range you choose)

Next, /etc/hostapd/hostapd.conf reads like this:

interface=wlan0
country_code=US
driver=nl80211
ssid=MyGreatSSID
hw_mode=g
channel=7
wmm_enabled=1
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=MyGreatPassword
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

Where MyGreatSSID is a substitute for the one I use. No quotes around it in the file, btw.. and MyGreatPassword is the substitute (in this example) for our actual password.

Last item, point hostapd to the file, editing /etc/default/hostapd:

Update this line: DAEMON_CONF= to this: DAEMON_CONF="/etc/hostapd/hostapd.conf"

There was an entry in /etc/rc.local to down the wlan0 interface that I changed it to bring it up; it was there from 'before', and I don't know if it comes that way by default or some previous project had left it there.

Reboot - and I was able to connect from Windows 10.