Ubuntu22.04 resolve.conf 設定スクリプト

Ubuntu22.04(Ubuntu server)でのresolve.conf 設定スクリプトです。
# 環境に合わせた修正箇所ここからを修正して使用してください。

スクリプト実行前の/etc/resolve.conf

cat /etc/resolv.conf

$ cat /etc/resolv.conf 
# This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
# Do not edit.
#
# This file might be symlinked as /etc/resolv.conf. If you're looking at
# /etc/resolv.conf and seeing this text, you have followed the symlink.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0 trust-ad
search .

スクリプト実行後

cat /etc/resolv.conf

$ cat /etc/resolv.conf 
nameserver 192.168.0.11
nameserver 192.168.0.1
options edns0 trust-ad
search .

スクリプトを新規作成します。

nano ubuntu_resolv_conf.sh

$ nano ubuntu_resolv_conf.sh

以下のスクリプトをコピーペーストします。# 設定内容ここからから # 環境に合わせた修正箇所ここまでを環境に合わせた値に修正して保存してください。

#!/bin/bash

### /etc/resolv.conf 設定スクリプトVer1
### 参考にさせていただいたURL 
# https://access.redhat.com/documentation/ja-jp/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/replacing-etc-resolv-conf-with-a-symbolic-link-to-manually-configure-dns-settings_manually-configuring-the-etc-resolv-conf-file

### 使い方
# nano ubuntu_resolv_conf.sh
# sudo chmod +x ubuntu_resolv_conf.sh
# ./ubuntu_resolv_conf.sh

# 設定内容ここから
# 1.既存のresolv.conf.manually-configured バックアップ
# 2.新規ファイル作成 /etc/resolv.conf.manually-configured
# 3./etc/resolv.conf 削除
# 4./etc/resolv.conf という名前のシンボリックリンクを作成
# 設定内容ここまで

# 動作確認
# lsb_release -a
#No LSB modules are available.
#Distributor ID:	Ubuntu
#Description:	Ubuntu 22.04 LTS
#Release:	22.04
#Codename:	jammy

# 環境に合わせた修正箇所ここから
# nameserver
DNS_IP="192.168.0.11"
DNS_IP2="192.168.0.1"
# options
OPT_WD="edns0 trust-ad"
# search
SEA_WD="." 
# 環境に合わせた修正箇所ここまで

# ----------- 処理ここから -----------
cd

make_resolv_conf_manually-configured() {
        # 新規resolv.conf.manually-configured 作成
        echo nameserver $DNS_IP > resolv.conf.manually-configured
        echo nameserver $DNS_IP2 >> resolv.conf.manually-configured
        echo options $OPT_WD >> resolv.conf.manually-configured  
        echo search $SEA_WD >> resolv.conf.manually-configured 
}

# /etc/resolv.conf.manually-configured 存在する場合
# 1.既存のresolv.conf.manually-configured バックアップ
if [ -e /etc/resolv.conf.manually-configured ]; then
        sudo mv /etc/resolv.conf.manually-configured /etc/resolv.conf.manually-configured.bak
fi

# 2.新規ファイル作成 /etc/resolv.conf.manually-configured
make_resolv_conf_manually-configured

sudo mv resolv.conf.manually-configured /etc/
sudo chown root:root /etc/resolv.conf.manually-configured

# 3./etc/resolv.conf 削除
sudo rm /etc/resolv.conf

# /etc/resolv.conf.manually-configured を参照する
# 4./etc/resolv.conf という名前のシンボリックリンクを作成
sudo ln -s /etc/resolv.conf.manually-configured /etc/resolv.conf
# ----------- 処理ここまで -----------

新規作成したスクリプトを実行可能にします。

sudo chmod +x ubuntu_resolv_conf.sh