作者: peterpang

Edit /etc/resolv.conf
add:

nameserver 8.8.8.8
nameserver 8.8.4.4

1. Update /etc/systemd/resolved.conf

[Resolve]
DNS=1.1.1.1 8.8.8.8
FallbackDNS=8.8.4.4

2. Restart system resolved: service systemd-resolved restart
3. Run systemd-resolve --status

the output should look like this:

Global
         DNS Servers: 1.1.1.1
                      8.8.8.8
...

Stop NetworkManager resets resolv.conf on every reboot

One way to stop Network Manager from adding dns-servers to /etc/resolv.conf file is to do this. So first open the nm conf file /etc/NetworkManager/NetworkManager.conf:

sudo vim /etc/NetworkManager/NetworkManager.conf

And add this to the [main] section:

dns=none

Save and exit.

Introduction

Virtual Network Computing, or VNC, is a connection system that allows you to use your keyboard and mouse to interact with a graphical desktop environment on a remote server. It makes managing files, software, and settings on a remote server easier for users who are not yet comfortable with the command line.

In this guide, you’ll set up a VNC server with TightVNC on an Ubuntu 20.04 server and connect to it securely through an SSH tunnel. Then, you’ll use a VNC client program on your local machine to interact with your server through a graphical desktop environment.

Prerequisites

To complete this tutorial, you’ll need:

• One Ubuntu 20.04 server with a non-root administrative user and a firewall configured with UFW. To set this up, follow our initial server setup guide for Ubuntu 20.04.
• A local computer with a VNC client installed. The VNC client you use must support connections over SSH tunnels:
  • On Windows, you can use TightVNC, RealVNC, or UltraVNC.
  • On macOS, you can use the built-in Screen Sharing program, or can use a cross-platform app like RealVNC.
  • On Linux, you can choose from many options, including vinagre, krdc, RealVNC, or TightVNC.

Step 1 — Installing the Desktop Environment and VNC Server

By default, an Ubuntu 20.04 server does not come with a graphical desktop environment or a VNC server installed, so you’ll begin by installing those.

You have many options when it comes to which VNC server and desktop environment you choose. In this tutorial, you will install packages for the latest Xfce desktop environment and the TightVNC package available from the official Ubuntu repository. Both Xfce and TightVNC are known for being lightweight and fast, which will help ensure that the VNC connection will be smooth and stable even on slower internet connections.

After connecting to your server with SSH, update your list of packages:

sudo apt update

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Now install Xfce along with the xfce4-goodies package, which contains a few enhancements for the desktop environment:

sudo apt install xfce4 xfce4-goodies

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During installation, you may be prompted to choose a default display manager for Xfce. A display manager is a program that allows you to select and log in to a desktop environment through a graphical interface. You’ll only be using Xfce when you connect with a VNC client, and in these Xfce sessions you’ll already be logged in as your non-root Ubuntu user. So for the purposes of this tutorial, your choice of display manager isn’t pertinent. Select either one and press ENTER.

Once that installation completes, install the TightVNC server:

sudo apt install tightvncserver

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Next, run the vncserver command to set a VNC access password, create the initial configuration files, and start a VNC server instance:

vncserver

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You’ll be prompted to enter and verify a password to access your machine remotely:

OutputYou will require a password to access your desktops.

Password:
Verify:

The password must be between six and eight characters long. Passwords more than 8 characters will be truncated automatically.

Once you verify the password, you’ll have the option to create a view-only password. Users who log in with the view-only password will not be able to control the VNC instance with their mouse or keyboard. This is a helpful option if you want to demonstrate something to other people using your VNC server, but this isn’t required.

The process then creates the necessary default configuration files and connection information for the server. Additionally, it launches a default server instance on port 5901. This port is called a display port, and is referred to by VNC as :1. VNC can launch multiple instances on other display ports, with :2 referring to port 5902, :3 referring to 5903, and so on:

OutputWould you like to enter a view-only password (y/n)? n
xauth:  file /home/sammy/.Xauthority does not exist

New 'X' desktop is your_hostname:1

Creating default startup script /home/sammy/.vnc/xstartup
Starting applications specified in /home/sammy/.vnc/xstartup
Log file is /home/sammy/.vnc/your_hostname:1.log

Note that if you ever want to change your password or add a view-only password, you can do so with the vncpasswd command:

vncpasswd

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At this point, the VNC server is installed and running. Now let’s configure it to launch Xfce and give us access to the server through a graphical interface.

Step 2 — Configuring the VNC Server

The VNC server needs to know which commands to execute when it starts up. Specifically, VNC needs to know which graphical desktop environment it should connect to.

The commands that the VNC server runs at startup are located in a configuration file called xstartup in the .vnc folder under your home directory. The startup script was created when you ran the vncserver command in the previous step, but you’ll create your own to launch the Xfce desktop.

Because you are going to be changing how the VNC server is configured, first stop the VNC server instance that is running on port 5901 with the following command:

vncserver -kill :1

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The output will look like this, although you’ll see a different PID:

OutputKilling Xtightvnc process ID 17648

Before you modify the xstartup file, back up the original:

mv ~/.vnc/xstartup ~/.vnc/xstartup.bak

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Now create a new xstartup file and open it in a text editor, such as nano:

nano ~/.vnc/xstartup

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Then add the following lines to the file:~/.vnc/xstartup

#!/bin/bash
xrdb $HOME/.Xresources
startxfce4 &

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The first line is a shebang. In executable plain-text files on *nix platforms, a shebang tells the system what interpreter to pass that file to for execution. In this case, you’re passing the file to the Bash interpreter. This will allow each successive line to be executed as commands, in order.

The first command in the file, xrdb $HOME/.Xresources, tells VNC’s GUI framework to read the server user’s .Xresources file. .Xresources is where a user can make changes to certain settings of the graphical desktop, like terminal colors, cursor themes, and font rendering. The second command tells the server to launch Xfce. Whenever you start or restart the VNC server, these commands will execute automatically.

Save and close the file after adding these lines. If you used nano, do so by pressing CTRL + X, Y, then ENTER.

To ensure that the VNC server will be able to use this new startup file properly, you’ll need to make it executable:

chmod +x ~/.vnc/xstartup

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Then restart the VNC server:

vncserver -localhost

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Notice that this time the command includes the -localhost option, which binds the VNC server to your server’s loopback interface. This will cause VNC to only allow connections that originate from the server on which it’s installed.

In the next step, you’ll establish an SSH tunnel between your local machine and your server, essentially tricking VNC into thinking that the connection from your local machine originated on your server. This strategy will add an extra layer of security around VNC, as the only users who will be able to access it are those that already have SSH access to your server.

You’ll see output similar to this:

OutputNew 'X' desktop is your_hostname:1

Starting applications specified in /home/sammy/.vnc/xstartup
Log file is /home/sammy/.vnc/your_hostname:1.log

With the configuration in place, you’re ready to connect to the VNC server from your local machine.

Step 3 — Connecting to the VNC Desktop Securely

VNC itself doesn’t use secure protocols when connecting. To securely connect to your server, you’ll establish an SSH tunnel and then tell your VNC client to connect using that tunnel rather than making a direct connection.

Create an SSH connection on your local computer that securely forwards to the localhost connection for VNC. You can do this via the terminal on Linux or macOS with the following ssh command:

ssh -L 59000:localhost:5901 -C -N -l sammy your_server_ip

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Here’s what this ssh command’s options mean:

• -L 59000:localhost:5901: The -L switch specifies that the given port on the local computer (59000) is to be forwarded to the given host and port on the destination server (localhost:5901, meaning port 5901 on the destination server, defined as your_server_ip). Note that the local port you specify is somewhat arbitrary; as long as the port isn’t already bound to another service, you can use it as the forwarding port for your tunnel.
• -C: This flag enables compression which can help minimize resource consumption and speed things up.
• -N: This option tells ssh that you don’t want to execute any remote commands. This setting is useful when you just want to forward ports.
• -l sammy your_server_ip: The -l switch let’s you specify the user you want to log in as once you connect to the server. Make sure to replace sammy and your_server_ip with the name of your non-root user and your server’s IP address.

Note: This command establishes an SSH tunnel that forwards information from port 5901 on your VNC server to port 59000 on your local machine via port 22 on each machine, the default port for SSH. Assuming you followed the prerequisite Initial Server Setup guide for Ubuntu 20.04, you will have added a UFW rule to allow connections to your server over OpenSSH.

This is more secure than simply opening up your server’s firewall to allow connections to port 5901, as that would allow anyone to access your server over VNC. By connecting over an SSH tunnel, you’re limiting VNC access to machines that already have SSH access to the server.

If you are using PuTTY to connect to your server, you can create an SSH tunnel by right-clicking on the top bar of the terminal window, and then clicking the Change Settings… option:

Find the Connection branch in the tree menu on the left-hand side of the PuTTY Reconfiguration window. Expand the SSH branch and click on Tunnels. On the Options controlling SSH port forwarding screen, enter 59000 as the Source Port and localhost:5901 as the Destination, like this:

Then click the Add button, and then the Apply button to implement the tunnel.

Once the tunnel is running, use a VNC client to connect to localhost:59000. You’ll be prompted to authenticate using the password you set in Step 1.

Once you are connected, you’ll see the default Xfce desktop. It should look something like this:

You can access files in your home directory with the file manager or from the command line, as seen here:

Press CTRL+C in your local terminal to stop the SSH tunnel and return to your prompt. This will disconnect your VNC session as well.

Now you can configure your VNC server to run as a systemd service.

Step 4 — Running VNC as a System Service

By setting up the VNC server to run as a systemd service you can start, stop, and restart it as needed, like any other service. You can also use systemd’s management commands to ensure that VNC starts when your server boots up.

First, create a new unit file called /etc/systemd/system/vncserver@.service:

sudo nano /etc/systemd/system/vncserver@.service

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The @ symbol at the end of the name will let us pass in an argument you can use in the service configuration. You’ll use this to specify the VNC display port you want to use when you manage the service.

Add the following lines to the file. Be sure to change the value of User, Group, WorkingDirectory, and the username in the value of PIDFILE to match your username:/etc/systemd/system/vncserver@.service

[Unit]
Description=Start TightVNC server at startup
After=syslog.target network.target

[Service]
Type=forking
User=sammy
Group=sammy
WorkingDirectory=/home/sammy

PIDFile=/home/sammy/.vnc/%H:%i.pid
ExecStartPre=-/usr/bin/vncserver -kill :%i > /dev/null 2>&1
ExecStart=/usr/bin/vncserver -depth 24 -geometry 1280x800 -localhost :%i
ExecStop=/usr/bin/vncserver -kill :%i

[Install]
WantedBy=multi-user.target

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The ExecStartPre command stops VNC if it’s already running. The ExecStart command starts VNC and sets the color depth to 24-bit color with a resolution of 1280×800. You can modify these startup options as well to meet your needs. Also, note that the ExecStart command again includes the -localhost option.

Save and close the file.

Next, make the system aware of the new unit file:

sudo systemctl daemon-reload

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Enable the unit file:

sudo systemctl enable vncserver@1.service

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The 1 following the @ sign signifies which display number the service should appear over, in this case the default :1 as was discussed in Step 2.

Stop the current instance of the VNC server if it’s still running:

vncserver -kill :1

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Then start it as you would start any other systemd service:

sudo systemctl start vncserver@1

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You can verify that it started with this command:

sudo systemctl status vncserver@1

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If it started correctly, the output should look like this:

Output● vncserver@1.service - Start TightVNC server at startup
     Loaded: loaded (/etc/systemd/system/vncserver@.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2020-05-07 17:23:50 UTC; 6s ago
    Process: 39768 ExecStartPre=/usr/bin/vncserver -kill :1 > /dev/null 2>&1 (code=exited, status=2)
    Process: 39772 ExecStart=/usr/bin/vncserver -depth 24 -geometry 1280x800 :1 (code=exited, status=0/SUCCESS)
   Main PID: 39795 (Xtightvnc)
...

Your VNC server is now ready to use whenever your server boots up, and you can manage it with systemctl commands like any other systemd service.

However, there won’t be any difference on the client side. To reconnect, start your SSH tunnel again:

ssh -L 59000:localhost:5901 -C -N -l sammy your_server_ip

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Then make a new connection using your VNC client software to localhost:59000 to connect to your server.

Conclusion

You now have a secured VNC server up and running on your Ubuntu 20.04 server. Now you’ll be able to manage your files, software, and settings with a user-friendly graphical interface, and you’ll be able to run graphical software like web browsers remotely.

The Issue

We want to convert our Ubuntu 20.04.1 LTS installation from BIOS to UEFI

Note

Before starting, we have to make sure that we have enough free disk space on the system disk (at least 1G, minimum 550MB probably will do as well)

There are many ways to

The Fix

1 Make sure the current hardware support both BIOS & UEFI, and the current Ubuntu installation is BIOS

Warning!!!: Before continuing, we must make sure that we have a full disk backup, although usually this type of conversion should not cause data loss, but there are still chances that data can get corrupted, so full disk backup is necessary.

2 Follow How to Convert Ubuntu 20.04.1 LTS OS disk from MBR to GPT/GPT to MBR without losing data to convert the disk first

(MBR with extent should not be an issue and should be able to be converted to GPT successfully)

Note 1: For this guide, we assume the disk we are converting is the only disk on the system, which means it is used for storing the operating system and user data

Note 2: For this guide, boot-repair-disk is preferred over Ubuntu Desktop Live (Although, we can use Ubuntu Desktop Live then install boot-repair on the live system too)

3 Boot from boot-repair-disk again

4 Launch GParted

5 Assume we only have one partition on the disk which is used for operating system itself and user data, we resize the partition then move the block with data to the end of the slide, so that we can have 550MB unallocated space at the beginning of the disk

6 Make sure the disk (partitions are unmounted first)

Click on Resize/Move button, Click on OK button on the warning screen, Click on the green Check button to commit the changes

7 Right Click on the unallocated space at the beginning, Click on New

8 For File system, Select Fat32, For Partition name, we enter EFI System Partition, Click on + Add button

9 Click on the green Check button to commit the changes

10 Right click on the fat32 partition that we have just created, Click on Manage Flags, Click on boot (boot and esp should be checked), Click on X Close button

11 Restart the system (Boot into BIOS/UEFI)

12 Change the settings to UEFI from BIOS

13 Boot from Boot Repair USB again

14 Click on No button if asked for updating the software

15 Click on the first button “Recommended repair (repairs most frequent problems)“

16 Carefully following the steps required by the Boot Repair software

17 When the boot repair is done without error, we need to restart the system (Remember to remove the bootable USB)

18 Now we should be able to boot into Ubuntu via UEFI

1 Download Ubuntu Desktop Live or boot-repair-disk

2 Create a bootable USB from the downloaded iso file using balenaEtcher or Ventoy suggested, refer to the following guides if necessary

List of free software/programs/Utilities to write ISO files to USB HDD/Thumb Drive/Flash Drive (Create bootable USB drives) easily etc. (balenaEtcher)

Another Simple and open source Multiboot USB creation tool (Ventoy)

3 Configure the BIOS/UEFI from the system which we want to convert the disk, so that we can boot it from USB (Refer to the motherboard manual or Search the motherboard model if necessary)

(If Boot Repair is asking to update the software, click on Nobutton)

4 Launch the terminal from the live system

5 We use the following command to convert the disk from MBR to GPT
(If gdisk is not installed, use sudo apt install gdisk to install it first)

sudo apt gdisk /dev/sdx

Note: Replace /dev/sdx with the correct disk label e.g. /dev/sda, /dev/sdb etc.

Output

GPT fdisk (gdisk) version 1.0.5
Partition table scan:
MBR: MBR only
BSD: not present
APM: not present
GPT: not present
***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
typing 'q' if you don't want to convert your MBR partitions
to GPT format!
***************************************************************
Command (? for help):

MBR to GPT

Enter w to convert MBR to GPT partition
Enter y to confirm and write the change

GPT to MBR

Enter r to enter the recover and transformation
Enter g to convert GPT to MBR partition

We can enter p to check the partitions.

Warning: We will lose our bootloader like grub, which means we will have to reinstall/fix the bootloader/grub etc. after the conversion, we can use boot-repair-disk from Step 1 to fix it easily by following steps prompted by the software