January 2024 ~ My Daily Works Archive

This tutorial will help you to Start/Stop and Restart the network services on a CentOS 8 or RHEL 8 Linux system. Here are the two methods available. We prefer method 1 to use.

Method 1 – Using NetworkManager Service

Use the followings commands to start/stop network service on your CentOS/RHEL 8 Linux system.

sudo systemctl start NetworkManager.service
sudo systemctl stop NetworkManager.service

Use the followings commands to restart network service on your CentOS/RHEL 8 Linux system.

sudo systemctl restart NetworkManager.service

Method 2 – Using nmcli Tool

The nmcli is the command-line utility for the managing NetworkManager on CentOS/RHEL 8 Linux system. You can simply use this utility to stop/start network service on your CentOS 8 or RHEL 8 system.

WARNING – Do not run nmcli networking off for the remotely connected systems. This will disable the NetworkManager network connections on the machine and you will lose connection.

sudo nmcli networking off
sudo nmcli networking on

The above command will disable/enable the network connections on CentOS 8 or RHEL 8 Linux system.

am a new Ubuntu Linux server user. How do I setup an OpenVPN Server on Ubuntu Linux version 18.04/20.04 LTS or 20.10 server to shield my browsing activity from bad guys on public Wi-Fi, and more?

OpenVPN is a full-featured SSL VPN (virtual private network). It implements OSI layer 2 or 3 secure network extension using the SSL/TLS protocol. It is an open source software and distributed under the GNU GPL. A VPN allows you to connect securely to an insecure public network such as wifi network at the airport or hotel. VPN is also required to access your corporate or enterprise or home server resources. You can bypass geo-blocked site and increase your privacy or safety online. This tutorial provides step-by-step instructions for configuring an OpenVPN “road warrior” server on Ubuntu Linux 18.04/20.04 LTS (20.10) version including ufw/iptables firewall configuration. The steps are as follows:

Find and note down your public IP address
Download openvpn-install.sh script
Run openvpn-install.sh to install OpenVPN server

Find your public IP address:

Use any one of the following command to find out your IPv4 public address. If your internface name is eth0 or eth1, enter:
$ ip addr show eth0
OR
$ ip addr show eth1

OR
$ ip a

[root@radius ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 74:56:3c:37:b4:2c brd ff:ff:ff:ff:ff:ff
inet 192.168.33.6/24 brd 192.168.33.255 scope global noprefixroute enp5s0
valid_lft forever preferred_lft forever
inet 59.152.XXX.XXX/29 brd 59.152.107.151 scope global noprefixroute enp5s0
valid_lft forever preferred_lft forever
inet 192.168.33.7/24 brd 192.168.33.255 scope global secondary noprefixroute enp5s0
valid_lft forever preferred_lft forever
3: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 100
link/none
inet 10.8.0.1/24 brd 10.8.0.255 scope global tun0
valid_lft forever preferred_lft forever
inet6 fe80::334f:6f01:66fc:20b6/64 scope link stable-privacy
valid_lft forever preferred_lft forever
[root@radius ~]#

Note down the public IPv4 address

59.152.XXX.XXX/29

Download openvpn-install.sh script to set up OpenVPN server in 5 minutes on Ubuntu

Type the following wget command or curl command:
$ wget https://git.io/vpn -O openvpn-install.sh

wget grabbing the script:

[root@radius ~]# wget https://git.io/vpn -O openvpn-install.sh
--2024-01-03 06:04:21-- https://git.io/vpn
Resolving git.io (git.io)... 140.82.114.21
Connecting to git.io (git.io)|140.82.114.21|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://raw.github.com/Nyr/openvpn-install/master/openvpn-install.sh [following]
--2024-01-03 06:04:23-- https://raw.github.com/Nyr/openvpn-install/master/openvpn-install.sh
Resolving raw.github.com (raw.github.com)... 185.199.108.133, 185.199.110.133, 185.199.111.133, ...
Connecting to raw.github.com (raw.github.com)|185.199.108.133|:443... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://raw.githubusercontent.com/Nyr/openvpn-install/master/openvpn-install.sh [following]
--2024-01-03 06:04:23-- https://raw.githubusercontent.com/Nyr/openvpn-install/master/openvpn-install.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.110.133, 185.199.109.133, 185.199.111.133, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.110.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 23714 (23K) [text/plain]
Saving to: ‘openvpn-install.sh’
openvpn-install.sh 100%[========================================================================================================================================>] 23.16K --.-KB/s in 0.008s
2024-01-03 06:04:24 (2.69 MB/s) - ‘openvpn-install.sh’ saved [23714/23714]
[root@radius ~]#

We can verify script using a text editor such as nano command or vim command:
$ vi openvpn-install.sh

Running openvpn-install.sh to install OpenVPN server

Type the following command:
$ sudo chmod +x openvpn-install.sh $ sudo bash openvpn-install.sh
Make sure you provide needed information:

[root@radius ~]# ./openvpn-install.sh
Welcome to this OpenVPN road warrior installer!

Which IPv4 address should be used?
1) 192.168.33.6
2) 59.152.107.147
3) 192.168.33.7
IPv4 address [1]: 2

Which protocol should OpenVPN use?
1) UDP (recommended)
2) TCP
Protocol [1]: 1

What port should OpenVPN listen to?
Port [1194]: 1194

Select a DNS server for the clients:
1) Current system resolvers
2) Google
3) 1.1.1.1
4) OpenDNS
5) Quad9
6) AdGuard
DNS server [1]: 3

Enter a name for the first client:
Name [client]: nextgen

OpenVPN installation is ready to begin.
Press any key to continue...
Notice
------
'init-pki' complete; you may now create a CA or requests.

Your newly created PKI dir is:
* /etc/openvpn/server/easy-rsa/pki

Using Easy-RSA configuration:
* undefined

No Easy-RSA 'vars' configuration file exists!

Using SSL:
* openssl OpenSSL 1.1.1k FIPS 25 Mar 2021
.................................+++++
..........+++++

Notice
------
CA creation complete. Your new CA certificate is at:
* /etc/openvpn/server/easy-rsa/pki/ca.crt

No Easy-RSA 'vars' configuration file exists!

Using SSL:
* openssl OpenSSL 1.1.1k FIPS 25 Mar 2021
Generating a RSA private key
.......................+++++
.....................................................................................................................+++++
writing new private key to '/etc/openvpn/server/easy-rsa/pki/44ea2e7f/temp.1.1'
-----

Notice
------
Private-Key and Public-Certificate-Request files created.
Your files are:
* req: /etc/openvpn/server/easy-rsa/pki/reqs/server.req
* key: /etc/openvpn/server/easy-rsa/pki/private/server.key

Using configuration from /etc/openvpn/server/easy-rsa/pki/openssl-easyrsa.cnf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
commonName :ASN.1 12:'server'
Certificate is to be certified until Dec 31 11:06:09 2033 GMT (3650 days)

Write out database with 1 new entries
Data Base Updated

Notice
------
Certificate created at:
* /etc/openvpn/server/easy-rsa/pki/issued/server.crt

Notice
------
Inline file created:
* /etc/openvpn/server/easy-rsa/pki/inline/server.inline

No Easy-RSA 'vars' configuration file exists!

Using SSL:
* openssl OpenSSL 1.1.1k FIPS 25 Mar 2021
Generating a RSA private key
..............................................................................................................+++++
.....................+++++
writing new private key to '/etc/openvpn/server/easy-rsa/pki/7b06327f/temp.1.1'
-----

Notice
------
Private-Key and Public-Certificate-Request files created.
Your files are:
* req: /etc/openvpn/server/easy-rsa/pki/reqs/nextgen.req
* key: /etc/openvpn/server/easy-rsa/pki/private/nextgen.key

Using configuration from /etc/openvpn/server/easy-rsa/pki/openssl-easyrsa.cnf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
commonName :ASN.1 12:'nextgen'
Certificate is to be certified until Dec 31 11:06:10 2033 GMT (3650 days)

Write out database with 1 new entries
Data Base Updated

Notice
------
Certificate created at:
* /etc/openvpn/server/easy-rsa/pki/issued/nextgen.crt

Notice
------
Inline file created:
* /etc/openvpn/server/easy-rsa/pki/inline/nextgen.inline

No Easy-RSA 'vars' configuration file exists!

Using SSL:
* openssl OpenSSL 1.1.1k FIPS 25 Mar 2021
Using configuration from /etc/openvpn/server/easy-rsa/pki/openssl-easyrsa.cnf

Notice
------
An updated CRL has been created:
* /etc/openvpn/server/easy-rsa/pki/crl.pem

Created symlink /etc/systemd/system/multi-user.target.wants/openvpn-iptables.service → /etc/systemd/system/openvpn-iptables.service.
Created symlink /etc/systemd/system/multi-user.target.wants/openvpn-server@server.service → /usr/lib/systemd/system/openvpn-server@.service.

Finished!

The client configuration is available in: /root/nextgen.ovpn
New clients can be added by running this script again.
[root@radius ~]#

Start/stop/restart OpenVPN server on Centos 8

Run the following systemctl command to stop the OpenVPN service:
$ sudo systemctl stop openvpn-server@server.service
Want to start it again? Try:
$ sudo systemctl start openvpn-server@server.service
The command to restart the OpenVPN service:
$ sudo systemctl restart openvpn-server@server.service
View status of your OpenVPN systemd based service:
$ sudo systemctl status openvpn-server@server.service

● openvpn-server@server.service - OpenVPN service for server
   Loaded: loaded (/usr/lib/systemd/system/openvpn-server@.service; enabled; vendor preset: disabled)
   Active: active (running) since Wed 2024-01-03 06:06:10 EST; 25min ago
     Docs: man:openvpn(8)
           https://community.openvpn.net/openvpn/wiki/Openvpn24ManPage
           https://community.openvpn.net/openvpn/wiki/HOWTO
 Main PID: 16020 (openvpn)
   Status: "Initialization Sequence Completed"
    Tasks: 1 (limit: 47953)
   Memory: 1.2M
   CGroup: /system.slice/system-openvpn\x2dserver.slice/openvpn-server@server.service
           └─16020 /usr/sbin/openvpn --status /run/openvpn-server/status-server.log --status-version 2 --suppress-timestamps --cipher AES-256-GCM --ncp-ciphers AES-256-GCM:AES-128-GCM:AES-256-CBC:AES-128-CBC:BF-CBC --config server.conf

Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: 59.152.105.235:64346 WARNING: 'keysize' is used inconsistently, local='keysize 256', remote='keysize 128'
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: 59.152.105.235:64346 Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, 2048 bit RSA
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: 59.152.105.235:64346 [nextgen] Peer Connection Initiated with [AF_INET]59.152.105.235:64346
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 MULTI_sva: pool returned IPv4=10.8.0.2, IPv6=(Not enabled)
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 MULTI: Learn: 10.8.0.2 -> nextgen/59.152.105.235:64346
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 MULTI: primary virtual IP for nextgen/59.152.105.235:64346: 10.8.0.2
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 PUSH: Received control message: 'PUSH_REQUEST'
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 SENT CONTROL [nextgen]: 'PUSH_REPLY,redirect-gateway def1 bypass-dhcp,dhcp-option DNS 1.1.1.1,dhcp-option DNS 1.0.0.1,block-outside-dns,route-gateway >
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 Outgoing Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key
Jan 03 06:07:55 radius.zoomonline.com.bd openvpn[16020]: nextgen/59.152.105.235:64346 Incoming Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key

Conclusion

And there you have it, OpenVPN server installed in five minutes to increase your privacy. Please see OpenVPN project and road warrior installer Linux script.

My Daily Works Archive

Restart Network Service on CentOS 8 or RHEL 8

Method 1 – Using NetworkManager Service

Method 2 – Using nmcli Tool

Set up OpenVPN Server In 5 Minutes on Centos8 Linux

Find your public IP address:

Download openvpn-install.sh script to set up OpenVPN server in 5 minutes on Ubuntu

Running openvpn-install.sh to install OpenVPN server

Conclusion

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