apt-get -y install hostapd dnsmasq

echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf
sysctl -p /etc/sysctl.conf
#
# Hostapd service is masked by default. This is the working way
# to unmask it and add to autostart:
#
echo "DAEMON_CONF=\"/etc/hostapd/hostapd.conf\"" >> /etc/default/hostapd
rm -f /etc/systemd/system/hostapd.service
ln -s /usr/lib/systemd/system/hostapd.service /etc/systemd/system/hostapd.service
systemctl daemon-reload

cat >> /etc/hostapd/hostapd.conf << EOF
interface=wlan0
driver=nl80211
country_code=UA
ssid=reise
# g means 2.4Ghz frequency:
hw_mode=g
# Enable 802.11n:
ieee80211n=1
wmm_enabled=1
channel=11
wpa=2
wpa_passphrase=nagorshkesidelkorol
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP
rsn_pairwise=CCMP
auth_algs=1
macaddr_acl=0
EOF

#
# WiFi interface cannot be assigned an IP address by netplan,
# unless Access Point is configured. Here is how to autoassign IP:
#
cat >> /etc/hostapd/wificonfig.sh << EOF
#!/bin/bash
ip addr add 192.168.20.29 dev wlan0
ip route add 192.168.20.0/24 dev wlan0 scope link src 192.168.20.29 metric 100
EOF

chmod 755 /etc/hostapd/wificonfig.sh

(crontab -l ; echo "@reboot sleep 20; /etc/hostapd/wificonfig.sh") | crontab -

cat >> /etc/dnsmasq.conf << EOF
strict-order
interface=wlan0
except-interface=lo
listen-address=192.168.20.29
bind-dynamic
dhcp-range=192.168.20.30,192.168.20.50,255.255.255.0,2h
dhcp-leasefile=/var/lib/misc/dnsmasq-wlan0.leases
#Let DHCP client recieve another DNS server, not local host:
#dhcp-option=option:dns-server,10.1.2.5,8.8.8.8
log-dhcp
# Create IP reserviation for known MAC:
dhcp-host=54:87:a2:19:95:f0,192.168.20.59
EOF

systemctl enable hostapd
systemctl start hostapd
systemctl enable dnsmasq
systemctl stop dnsmasq
systemctl start dnsmasq

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
service netfilter-persistent save