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#!/bin/bash
# Author: Steven Shiau, <steven _at_ clonezilla org>
# License: GPL
# Program to get DNS server
# Load DRBL setting and functions
DRBL_SCRIPT_PATH="${DRBL_SCRIPT_PATH:-/usr/share/drbl}"
. $DRBL_SCRIPT_PATH/sbin/drbl-conf-functions
#
# Settings
DNS_sys="/etc/resolv.conf"
Usage() {
echo "Get the DNS server IP address for system."
echo "Usage:"
echo "$(basename $0)"
echo "Ex: $(basename $0)"
}
#
while [ $# -gt 0 ]; do
case "$1" in
-*) echo "${0}: ${1}: invalid option" >&2
Usage >&2
exit 2 ;;
*) break ;;
esac
done
nameserver_sys="$(LC_ALL=C grep -Ew "^nameserver" $DNS_sys | awk -F" " '{print $2}')"
if [ -z "$nameserver_sys" -o -n "$(echo "$nameserver_sys" | grep -E "^127\..*")" ]; then
# On Ubuntu, dnsmasq with network-manager, the result might 127.0.0.1. We use nm-tool to get the real one
# Ubuntu >= 22.04, use "resolvectl status"
# Ubuntu >= 17.10 or Debian >= 9, use "systemd-resolve --status"
# Ubuntu <= 14.04, use "nmcli dev list", while > 14.04, "nmcli dev show".
# Results of systemd-resolve --status, example:
# DNS Servers: 8.8.8.8
# 8.8.4.4
# or
# DNS Servers: 8.8.8.8
# 8.8.4.4
# 168.95.1.1
# DNSSEC NTA: 10.in-addr.arpa
nameserver_sys="$(LC_ALL=C resolvectl status 2>/dev/null | grep -E "^[[:space:]]*DNS Servers" | awk -F":" '{print $2}')"
if [ -z "$nameserver_sys" ]; then
nameserver_sys="$(LC_ALL=C resolvectl status 2>/dev/null | sed -r -n '/DNS Servers:/,/(^$|^[[:print:]]*:[[:space:]]+.*)/p' | sed -r -e "s/DNS Servers://g")"
# Decide the last line if it's the IP address.
last_line="$(LC_ALL=C echo "$nameserver_sys" | tail -n 1 | grep -E "^[[:print:]]*:[[:space:]]+.*$")"
fi
if [ -n "$last_line" ]; then
# Do not show the last line, remove it.
nameserver_sys="$(echo "$nameserver_sys" | head -n -1)"
fi
if [ -z "$nameserver_sys" ]; then
nameserver_sys="$(LC_ALL=C nmcli dev show 2>/dev/null | grep -i "IP4.DNS" | awk -F " " '{print $2}')"
fi
if [ -z "$nameserver_sys" ]; then
nameserver_sys="$(LC_ALL=C nmcli dev list 2>/dev/null | grep -i "IP4.DNS" | awk -F " " '{print $2}')"
fi
if [ -z "$nameserver_sys" ]; then
# Last posibility, dnsmasq
nameserver_sys="$(LC_ALL=C grep -Ew "^nameserver" /var/run/dnsmasq/resolv.conf 2>/dev/null | awk -F" " '{print $2}')"
fi
fi
sys_dns=""
# For multiple NIC configured with DNS,
# nameserver_sys can be like: '8.8.8.8 DNS Domain: ~. 8.8.8.8 DNS Domain: ~. '
# Hence we only put correct IPv4 address.
# Ref: https://groups.google.com/g/drbl/c/ebgoMdLIo9c
# Thanks to Alber Yang (alber.yang _at_ gmail com) for reporting this issue.
for i in $nameserver_sys; do
if `is_valid_IPv4_add $i`; then
sys_dns="$sys_dns, $i"
fi
done
# Strip the leading ", "
echo "$(echo $sys_dns | sed -r -e "s/^, //")"
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