How to Configure Networks on A Ubuntu Server?

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Configuring networks on an Ubuntu server involves modifying certain configuration files and settings to establish successful network connectivity. Here are the steps to do so:

  1. Open a terminal: Launch a terminal emulator to access the command-line interface on your Ubuntu server.
  2. Locate the network configuration file: Navigate to the /etc/netplan/ directory, which contains the network configuration file named "01-netcfg.yaml". Use the command "cd /etc/netplan/" to change the directory.
  3. Open the configuration file: Use a text editor such as Nano or Vim to open the network configuration file. For instance, run the command "sudo nano 01-netcfg.yaml".
  4. Configure network settings: Within the configuration file, you will find a section named "network". Here you can define network interfaces, their IP addresses, subnet masks, gateways, DNS servers, etc.
  5. Understand the configuration syntax: Pay attention to the YAML syntax used in the configuration file. Indentation is crucial in YAML, so make sure to maintain proper spacing and indentation while defining network parameters.
  6. Define network interfaces: Add or modify entries for network interfaces under the "network" section in the format: "ethernets": - "interface_name": "addresses": ["ip_address/subnet_mask"] "gateway4": "gateway_ip_address" "nameservers": "addresses": ["DNS_server_ip_address"] Replace "interface_name" with the actual name of your network interface (e.g., eth0, eth1). Enter the appropriate IP address, subnet mask, gateway, and DNS server values as required.
  7. Configure additional network interfaces: If you have multiple network interfaces, add or modify entries for each interface using the same format as above.
  8. Save the configuration file: After making the necessary changes, save the configuration file and exit the text editor.
  9. Apply the network configuration: Apply the new network configuration by running the command "sudo netplan apply". This will activate the changes you made to the network settings.
  10. Verify network connectivity: Verify that the network configuration is working by testing the network connection using commands like "ping" or "nslookup". For example, running "ping google.com" should indicate successful connectivity if the configuration is correct.


Remember to ensure the accuracy of the entered IP addresses, gateways, and DNS servers. Improper configuration can lead to network connectivity issues.

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Can I configure multiple IP addresses on a single network interface in Ubuntu server?

Yes, you can configure multiple IP addresses on a single network interface in Ubuntu Server. This can be done by creating multiple virtual network interface cards (subinterfaces) using the primary network interface.


Here's a step-by-step guide to configure multiple IP addresses on a single network interface in Ubuntu Server:

  1. Open the network configuration file for editing. The file is usually located at /etc/netplan/ and named something like 01-netcfg.yaml.
  2. Add a new configuration block for the primary interface and specify the IP address, subnet mask, and gateway. For example:
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network:
  version: 2
  renderer: networkd
  ethernets:
    ens160:
      dhcp4: no
      addresses: [192.168.0.10/24]
      gateway4: 192.168.0.1


Replace ens160 with the name of your primary network interface.

  1. Now, add additional address blocks under the primary interface configuration to assign multiple IP addresses to the same interface. For example, to add two more IP addresses, you can use:
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ethernets:
  ens160:
    dhcp4: no
    addresses:
      - 192.168.0.10/24
      - 192.168.0.20/24
      - 192.168.0.30/24
    gateway4: 192.168.0.1


  1. After making the necessary changes, save the file and exit the editor.
  2. Apply the changes by running the following command in the terminal:
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sudo netplan apply


Once the changes are applied, your network interface will have multiple IP addresses assigned to it. You can verify the configuration by using the ip addr or ifconfig command.


What command can be used to renew an IP address in Ubuntu server?

In Ubuntu server, you can use the dhclient command to renew an IP address.


What is the default network configuration file in Ubuntu server?

The default network configuration file in Ubuntu Server is "/etc/netplan/01-netcfg.yaml".

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How can I configure a proxy server on Ubuntu server?

To configure a proxy server on Ubuntu server, you can follow these steps:

  1. Install the Squid proxy server by running the following command: sudo apt update sudo apt install squid
  2. Once the installation is complete, modify the Squid configuration file by opening it with a text editor: sudo nano /etc/squid/squid.conf
  3. Find the line that starts with "http_port" and update it with the desired port number. By default, it is set to port 3128.
  4. Configure the allowed clients to access the proxy server by adding the following lines: acl allowed_clients src http_access allow allowed_clients Replace with the IP range or specific IP address of the client machines allowed to access the proxy server. Use "0.0.0.0/0" to allow all IP addresses.
  5. (Optional) If you want to enable authentication, uncomment the following lines by removing the "#" at the beginning: #auth_param basic program /usr/lib/squid/basic_ncsa_auth /etc/squid/passwd #auth_param basic children 5 #auth_param basic realm Squid proxy-caching web server #auth_param basic credentialsttl 2 hours #auth_param basic casesensitive on #auth_param basic utf8 on #acl auth_users proxy_auth REQUIRED #http_access allow auth_users Set a username and password in the /etc/squid/passwd file by running the following command: sudo htpasswd -c /etc/squid/passwd Replace with the desired username.
  6. Save the changes and exit the text editor.
  7. Restart the Squid proxy server for the changes to take effect: sudo systemctl restart squid


That's it! Your proxy server is now configured on Ubuntu server. You can configure your client machines to use the proxy server by setting the appropriate proxy settings in the browser or system network settings.


How can I assign a static IP address to my Ubuntu server?

To assign a static IP address to your Ubuntu server, you can follow these steps:

  1. Identify the network interface: Open a terminal and run the command: ifconfig or ip addr show. This will display a list of network interfaces. Identify the interface you want to assign the static IP address to (e.g., eth0, ens33, enp0s3).
  2. Configure the network interface: Open the network configuration file for the interface you identified in the previous step. The file's location may vary based on the Ubuntu version; for recent versions (e.g., Ubuntu 18.04), it is located at /etc/netplan/. Look for a file with a .yaml extension, typically named something like 50-cloud-init.yaml or 01-netcfg.yaml. Open the file using a text editor.
  3. Update the network configuration file: Inside the file, you should see a section specifying the network interface and its configuration (e.g., addresses, dhcp). Modify the configuration to assign a static IP address instead of using DHCP. Replace the existing lines, if any, with the following (replace and with your desired values): network: version: 2 renderer: networkd ethernets: : addresses: [/subnet_bits] gateway4: nameservers: addresses: [, ] For example, your updated configuration might look like this: network: version: 2 renderer: networkd ethernets: ens33: addresses: [192.168.1.100/24] gateway4: 192.168.1.1 nameservers: addresses: [8.8.8.8, 8.8.4.4]
  4. Apply the changes: Once you've made the necessary changes to the network configuration file, save the changes and exit the text editor. Apply the new configuration by running the command: sudo netplan apply This will apply the new network configuration and assign the static IP address to the specified interface.
  5. Verify the changes: You can use the ifconfig or ip addr show command again to verify that the network interface now has the static IP address assigned.


That's it! Your Ubuntu server should now have a static IP address assigned to the specified network interface.

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