#!/bin/bash
# Get clean Debian installation ready for use in GNS3


user='debian'
pass='debian'

ttyS0_service='/lib/systemd/system/ttyS0.service'


# Check if I am root
 [ "$(id -u)" != 0 ] && echo "Run the script as root, exiting" && exit 1 

# Update packages
 apt-get update
 [ "$?" != 0 ] && echo "System can't be updated, exiting" && exit 1

# Check if we utilities are installed -  net-tools to manage interfaces instead netplan
 for package in net-tools vim; do
  dpkg --list | grep "$package" &>/dev/null
  [ "$?" == 1 ] && sudo apt-get -y install "$package"
 done

# Check if ipv4 and ipv6 forwarding are enabled"
    ipv4_fwd="$(sysctl net.ipv4.ip_forward | cut -d ' ' -f3)"
    ipv6_fwd="$(sysctl net.ipv6.conf.all.forwarding | cut -d ' ' -f3)"

    if [ "$ipv4_fwd" == 0 ]; then
       sysctl -w net.ipv4.ip_forward=1
       sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/g' /etc/sysctl.conf
       echo "I have enabled IPv4 forwarding"
    elif [ "$ipv4_fwd" == 1 ]; then 
       echo "IPv4 forwarding is enabled between interfaces, nothing to do"
    else
       echo "IPv4 forwarding between interfaces is not enabled, exiting"
    exit 1
    fi    

   if [ "$ipv6_fwd" == 0 ]; then
       sysctl -w net.ipv6.conf.all.forwarding=1
       sed -i 's/#net.ipv6.conf.all.forwarding/net.ipv6.conf.all.forwarding/g' /etc/sysctl.conf
       echo "I have enabled IPv6 forwarding"
    elif [ "$ipv6_fwd" == 1 ]; then 
       echo "IPv6 forwarding is enabled between interfaces, nothing to do"
    else
       echo "IPv6 forwarding between interfaces is not enabled, exiting"
    exit 1
    fi    
        
# Stop renaming interface e.g. eth0 to ens3
 sed -i 's/GRUB_CMDLINE_LINUX=""/GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"/g' /etc/default/grub
 grub-mkconfig -o /boot/grub/grub.cfg

# Redirect video output to serial console
 echo '[Unit]' > "$ttyS0_service"
 echo -e "Description=Serial Console Service\n" >> "$ttyS0_service"
 echo '[Service]' >> "$ttyS0_service"
 echo 'ExecStart=/sbin/getty -L 115200 ttyS0 vt102' >> "$ttyS0_service"
 echo -e "Restart=always\n" >> "$ttyS0_service"
 echo '[Install]' >> "$ttyS0_service"
 echo 'WantedBy=multi-user.target' >> "$ttyS0_service"

 systemctl daemon-reload
 systemctl enable ttyS0
 systemctl start ttyS0
 
 
# Reduce timeout for network interfaces to 15sec during boot
 mkdir -p /etc/systemd/system/networking.service.d
 echo "[Service]" > /etc/systemd/system/networking.service.d/reduce-timeout.conf
 echo "TimeoutStartSec=15" >> /etc/systemd/system/networking.service.d/reduce-timeout.conf

# Add path to .bashrc
echo 'export PATH=$PATH:/usr/local/sbin:/usr/sbin:/usr/bin' >> /home/$user/.bashrc 

# Print login credential before login
 echo \n >> 
 echo "Username/password: $user/$pass" >> /etc/issue
 

exit 0