====== Ubuntu 20.04 設定 OpenVPN Client 自動連上方式 ======
因為 Server 與 Server 的聯繫要透過 OpenVPN 所以有這個需求, 本來以為可能要花一些時間寫 script , 測試結果發現非常簡單就可以搞定.

===== 安裝 OpenVPN 套件 =====
  * <cli>
sudo apt update
sudo apt install openvpn -y
</cli>

===== 設定 OpenVPN Client =====
  * 先透過 OpenVPN Server 取得到相關的憑證設定檔, Exp. amalia_gpu.ovpn
  * 將取得的 amalia_gpu.ovpn 放入 /etc/openvpn/ 內 <file>
root@amalia:/etc/openvpn# pwd
/etc/openvpn
root@amalia:/etc/openvpn# ls
amalia_gpu.ovpn  client  server  update-resolv-conf
</file>
  * 透過手動命令列方式來確認是否設定檔都正確  openvpn --config amalia_gpu.ovpn <code sh>
root@amalia:/etc/openvpn# openvpn --config amalia_gpu.ovpn
Jun  2 19:18:20 OpenVPN 2.4.7 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Mar 22 2022
Jun  2 19:18:20 library versions: OpenSSL 1.1.1f  31 Mar 2020, LZO 2.10
Jun  2 19:18:20 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
Jun  2 19:18:20 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
:
:
Jun  2 19:18:23 /sbin/ip route add 10.20.0.0/24 via 10.121.101.73
Jun  2 19:18:23 /sbin/ip route add 10.50.1.0/24 via 10.121.101.73
Jun  2 19:18:23 /sbin/ip route add 10.121.101.0/24 via 10.121.101.73
</code>
  * 將 範例的 amalia_gpu.ovpn 改成 client.conf 然後將 openvpn 服務啟動就會自動連上 <cli>
cp amalia_gpu.ovpn client.conf
</cli>
  * 設定開機自動連上去 VPN Server <cli>
sudo vi /etc/default/openvpn
</cli><file>
:
AUTOSTART="all"
:
</file><cli>
sudo systemctl enable openvpn@client.service
sudo systemctl daemon-reload
sudo service openvpn@client start
</cli>
  * 確認連上 OpenVPN Server 所取得的 IP <cli>
ip a | grep tun
</cli>結果如下<cli>
root@amalia:/etc/openvpn# ip a | grep tun
11: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 100
    inet 10.121.101.74 peer 10.121.101.73/32 scope global tun0
</cli>可知道 openvpn 取得到的 ip 是 10.121.101.74

===== 取消與關閉 openvpn =====
  * <cli>
sudo service openvpn@client stop
sudo systemctl disable openvpn@client.service
sudo systemctl daemon-reload
</cli>
  * 確認已經沒有連上 OpenVPN Server 所取得的 IP <cli>
ip a | grep tun
</cli>結果應該不會出現任何 ip


===== 參考網址 =====
  * https://tecadmin.net/install-openvpn-client-on-ubuntu/
  * https://www.ivpn.net/knowledgebase/linux/linux-autostart-openvpn-in-systemd-ubuntu/

{{tag>openvpn}}