Pi won't reload etc/network/interfaces: Won't switch back to DHCP after static IP removed and networking restarted

Question

I'm following these instructions to create an Ad-Hoc WiFi network from a Pi Zero W. It works great. Problem is, once I'm done I want to switch the Pi back to DHCP and log on to my house WiFi like normal.

1) Replace the old files: /etc/dhcpcd.conf and /etc/network/interfaces to their original states from a backup before the Ad-Hoc instructions were followed

2) I'm trying to restart networking with:

sudo ifdown wlan0
sudo ifup wlan0

... and I've tried all these commands as well following that:

sudo service networking restart
sudo /etc/init.d/networking restart
sudo systemctl daemon-reload

No matter what I try, I can't get the Pi to give up it's static IP and connect normally back to my home WiFi... UNTIL I restart the computer. How else can I force the network to reload /etc/network/interfaces without powering cycling?

EDIT:

Here's the interfaces file BEFORE adhoc, which is restored AFTER adhoc:

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto wlan0

auto lo usb0
iface lo inet loopback

iface eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1
iface wlan1 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug usb0
iface usb0 inet manual

during adhoc the wlan0 part is changed to:

allow-hotplug wlan0
iface wlan0 inet static
    address 192.168.0.1
    netmask 255.255.255.0
    network 192.168.0.0

...and that's the problem, I can't "clear" that static IP address so the Pi won't connect to my router.

Answer 1

sudo service networking restart will DO NOTHING on a normal Raspbian, because it is not using networking it is using dhcpcd.

Try this:

sudo systemctl daemon-reload  
sudo systemctl start dhcpcd.service
# or if dhcpcd is already running:
sudo systemctl restart dhcpcd.service

It is not clear what other services you may have started, so you should investigate and stop these.