Disable IPv6 on Linux

DisableIPv6.sh

#!/bin/bash
# set -x

##
# This is only needed in some occasions, please don't use this unless you know what you're doing.
# Installs/Uninstalls sysctl configuration disable IPv6 at the kernel level
#
# @AUTHOR: Matt Spurrier (@DigitalSparky) | https://digitalsparky.com | https://github.com/digitalsparky
# @LICENSE GPLv3
##

OUTFILE="/etc/sysctl.d/99-ipv6-disable.conf"

__disablev6_activate_sysctl_config() {
  sysctl --system > /dev/null
  if [ "$?" -gt 0 ]; then
    __disablev6_term_revert
  fi
}

__disablev6_write_sysctl_config() {
  echo "Adding configuration to ${OUTFILE}..."
  cat <<EOF > "${OUTFILE}"
net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
EOF
}

__disablev6_revert_config() {
  rm -f "${OUTFILE}"
  __disablev6_activate_sysctl_config
}

__disablev6_term_revert() {
  echo "Configuration failed to apply, reverting."
  __disablev6_revert_config
  exit 255
}

__disablev6_root_check() {
  if [[ "$UID" -ne 0 ]]; then
    echo "This script must be run as root."
    exit 126
  fi
}

__disablev6_uninstall() {
  __disablev6_root_check
  __disablev6_revert_config
  echo "Uninstallation Complete!"
}

__disablev6_install() {
  __disablev6_root_check
  __disablev6_write_sysctl_config
  __disablev6_activate_sysctl_config
  echo "Configuration Complete!"
  echo "If you need to reverse this, simply run:"
  echo "$0 --uninstall"
}

__disablev6_help() {
  cat <<EOF
Linux IPv6 Disable/Enable

$0 [--install|--uninstall|--help]

--install: Installs the sysctl configuration to disable IPv6 and activates it
--uninstall: Uninstalls the sysctl configuration to disable IPv6 and activates the changes
--help: Prints this help screen

EOF
  exit 0
}

trap '__disablev6_term_revert' TERM

case $1 in
  "--install")
    __disablev6_install
    ;;
  "--uninstall")
    __disablev6_uninstall
    ;;
  "--help")
    __disablev6_help
    ;;
  *)
    __disablev6_help
    ;;
esac