FINALLY SOLVED: Thanks to @tom
(added chmod and complete procedure for other users)

1. First create a script:

vi /usr/bin/rb5-wifi-static-ip.sh 

Content of rb5-wifi-static-ip.sh script (with sample IP):

#!/bin/bash

rb5_net='192.168'
drone_IP='192.168.178.201'
router_IP='192.168.178.1'
netmask_IP='255.255.255.0'
network_interface='wlan0'

# wait for wlan to get it's initial IP from router
rb5-net-check $network_interface $rb5_net

# set new IP
sudo ifconfig $network_interface $drone_IP netmask $netmask_IP
sudo route add default gw $router_IP $network_interface

2. Give permission to script (if not, will give you message "Permission denied"):

chmod u+x /usr/bin/rb5-wifi-static-ip.sh

3. Create a service:

vi /etc/systemd/system/rb5-wifi-static-ip.service

Content of rb5-wifi-static-ip.service file:

[Unit]
Description=WLAN0 Static IP Service
After=wlan_daemon.service

[Service]
ExecStart=/usr/bin/rb5-wifi-static-ip.sh

[Install]
WantedBy=multi-user.target

4. Enable this service when RB5 boots:

systemctl enable rb5-wifi-static-ip.service

Restart RB5 and you will have a static IP!

@tom & @Eric-Katzfey

List of services: (command to show active services)

systemctl list-units --type=service

Some services are down like:
● dnsmasq.service loaded failed failed dnsmasq - A lightweight DHCP and caching DNS server
● lunch-make-scripts.service loaded failed failed lunch make scripts
● mystatic-ip.service loaded failed failed My static IP

Somebody could please help me?

NOT RESOLVED @Eric-Katzfey & @tom

Works on Reboot but not if I turn RB5 OFF wait a wile and afterwards I turn it ON

Sometimes work and sometimes doesn't

Somebody could please help me?

RESOLVED: Thanks to @Eric-Katzfey & @tom

1. First create a script:

vi /etc/sudoers.d/mystatic-ip.sh

Content of mystatic-ip.sh script:

#!/bin/bash
sudo ifconfig wlan0 192.168.178.201 netmask 255.255.255.0
sudo route add default gw 192.168.178.1 wlan0

2. Create a service:

vi /etc/systemd/system/mystatic-ip.service

Content of mystatic-ip.service file (that starts after wlan daemon):

[Unit]
Description=My static IP
After=wlan_daemon.service

[Service]
ExecStart=/etc/sudoers.d/mystatic-ip.sh start

[Install]
WantedBy=multi-user.target

To enable this service when the RB5 boots:

systemctl enable mystatic-ip

Reboot and you will have a static IP!

@Eric-Katzfey
Thank you for help, what would you suggest? Perhaps a delay in the script or something similar?
how do you suggest to do the startup log? and how could this sequence be organized correctly?
Do you have a RB5 to test? Thank you for any help

@tom
Thank you for reply, yes If I run:

sudo ifconfig wlan0 192.168.178.201 netmask 255.255.255.0
sudo route add default gw 192.168.178.1 wlan0

works, but if I restart RB5 the script does not do his work, perhaps a chmod is needed?

@tom Thank you
But perhaps i did something wrong creating a script:

vi /etc/sudoers.d/mystatic-ip.sh

Content of mystatic-ip.sh file:

#!/bin/bash
sudo ifconfig wlan0 192.168.178.201 netmask 255.255.255.0
sudo route add default gw 192.168.178.1 wlan0

Then i created a service:

vi /etc/systemd/system/mystatic-ip.service

Content of mystatic-ip.service file:

[Unit]
Description=My static IP

[Service]
ExecStart=/etc/sudoers.D/mystatic-ip.sh start

[Install]
WantedBy=multi-user.target

To enable this service when startup I did:

systemctl enable mystatic-ip

I don't know what I did wrong. Could you please help me?
Robert

I would like to set a static IP.
I thought that maybe in UBUNTU you could set it as follows:

sudo vi /etc/dhcpcd.conf

I tried with the WiFi network wlan0 and set an IP compatible with my network: 192.168.178.201

# on the server to actually work
option rapid_commit

# A list of options to request from the DHCP server
option domain_name_servers, domain_name, domain_search, host_name
option classless_static_routes
# Most distributions have NTP support.
option ntp_servers
# Respect the network MTU. This is applied to DHCP routes.
option interface_mtu

# A ServerID is required by RFC2131.
require dhcp_server_identifier

# Generate Stable Private IPv6 Addresses instead of hardware based ones
slaac private

# ==== Test of static IP configuration: ======
interface wlan0
static ip_address=192.168.178.201/24
static routers=192.168.178.1
static domain_name_servers=8.8.8.8

But when I turn RB5 off and on again sometimes it works with right static IP 192.168.178.201 and sometimes with a random IP, I don't know what I did wrong. Could you please help me?
Robert