How to create hotspot without internet connection?

A simple solution is to use create_ap. From their site:

create_ap is a tool that helps you create an open, or encrypted AP at any channel, hide your SSID, disable communication between clients (client isolation), IEEE 802.11n & 802.11ac support, Internet sharing methods: NATed or Bridged or None (no Internet sharing)

For your case you want to create an AP with the linux pc without sharing the internet from your dongle to clients, but can do other Lan stuff, like file sharing.

Your wifi card needs to support creating AP

Install some packages:

sudo apt install util-linux bash procps hostapd iproute2 iw haveged net-tools dnsmasq iptables

Get the create_ap package. From the terminal do

git clone https://github.com/oblique/create_ap
cd create_ap
sudo make install

After installation, check the name of your modem and wifi card with ifconfig (deprecated) or:
```
iwconfig
```
the wifi card usually is wlan0 or wlp2s0 and usb modem is eth0. yours might be different
Now start hotspot from your linux without internet:
```
sudo create_ap -n wlp2s0 MyAccessPoint
```

You can then connect clients. Your internet would not be shared but you can do samba and other things without internet

Here is a script that will create Hotspot but not share the Ethernet Internet with the WiFi devices. You will have to change the network interface name according to your system.

Type ip link to find them. Also, make sure you have installed dnsmasq and hostapd.

sudo apt-get install ifconfig dnsmasq hostapd

Before running the script you will have to stop any Network Management Tool which is controlling WiFi.

eth-to-wifi-route.sh

#!/bin/bash

# Share Eth with WiFi Hotspot
#
# This script is created to work with Raspbian Stretch
# but it can be used with most of the distributions
# by making few changes. 
#
# Make sure you have already installed `dnsmasq` and `hostapd`
# Please modify the variables according to your need
# Don't forget to change the name of network interface
# Check them with `ifconfig`

ip_address="192.168.2.1"
netmask="255.255.255.0"
dhcp_range_start="192.168.2.2"
dhcp_range_end="192.168.2.100"
dhcp_time="12h"
eth="eth0" # replace it with Huawei 3G Modem interface
wlan="wlan0"
ssid="Arpit-Raspberry"
psk="arpit1997"

sudo rfkill unblock wlan &> /dev/null
sleep 2

#sudo iptables -F
#sudo iptables -t nat -F
#sudo iptables -t nat -A POSTROUTING -o $eth -j MASQUERADE  
#sudo iptables -A FORWARD -i $eth -o $wlan -m state --state RELATED,ESTABLISHED -j ACCEPT  
#sudo iptables -A FORWARD -i $wlan -o $eth -j ACCEPT 

#sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

sudo ifconfig $wlan $ip_address netmask $netmask

sudo ip route del 0/0 dev $wlan &> /dev/null
a=`route | awk "/${eth}/"'{print $5+1;exit}'`
sudo route add -net default gw $ip_address netmask 0.0.0.0 dev $wlan metric $a

echo -e "interface=$wlan \n\
bind-interfaces \n\
server=8.8.8.8 \n\
domain-needed \n\
bogus-priv \n\
dhcp-range=$dhcp_range_start,$dhcp_range_end,$dhcp_time" > /etc/dnsmasq.conf

sudo systemctl restart dnsmasq

echo -e "interface=$wlan\n\
driver=nl80211\n\
ssid=$ssid\n\
hw_mode=g\n\
ieee80211n=1\n\
wmm_enabled=1\n\
macaddr_acl=0\n\
auth_algs=1\n\
ignore_broadcast_ssid=0\n\
wpa=2\n\
wpa_key_mgmt=WPA-PSK\n\
wpa_passphrase=$psk\n\
rsn_pairwise=CCMP" > /etc/hostapd/hostapd.conf

sudo systemctl restart hostapd
sudo systemctl status hostapd &> /dev/null
if [ "$?" != 0 ];then
    echo "Some Network Management tool is running, which is stopping" 
    echo "hostapd to be configured."
    echo "Please stop that and again run the script."
fi

I have commented the iptable and packet forwarding commands. If anytime you need to give internet to the devices just uncomment them.

Run the script

sudo bash eth-to-wifi-route.sh

Source: eth-to-wifi-route.sh

How to create hotspot without internet connection?

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