- Install any virtualization hypervisor, such as VirtualBox.
- Create a virtual machine and install any distribution of the Linux operating system, such as Debian.
- Use cloning of the virtual machine to create second virtual machine.
- Make sure that virtual machines can connect over a network using NAT, Internal Network, and Bridged Adapter.
Commonly used hypervisors:
Important reserved address blocks on an Internet network:
| Address block | Interval | No. of addresses | Description |
|---|---|---|---|
| 10.0.0.0/8 | 10.0.0.0 - 10.255.255.255 | 16.777.216 | Local addresses |
| 127.0.0.0/8 | 127.0.0.0 - 127.255.255.255 | 16.777.216 | Loopback addresses |
| 169.254.0.0/16 | 169.254.0.0 - 169.254.255.255 | 65.536 | Link-Local addresses |
| 172.16.0.0/12 | 172.16.0.0 - 172.31.255.255 | 1.048.576 | Local addresses |
| 192.168.0.0/16 | 192.168.0.0 - 192.168.255.255 | 65.536 | Local addresses |
| 224.0.0.0/4 | 224.0.0.0 - 239.255.255.255 | 268435456 | Multicast addresses |
The ip command allows us to display and manage network devices, network adapters, tunnels, and routing.
The ping command allows us to send ICMP ECHO_REQUEST packets to the selected network device based on its IP address.
The apt-get command is a package manager that allows us to install, modify, and delete programs, and search software through accessible repositories.
The su command allows us to change the user by running commands in the shell.
The mkdir command is used to create new directories.
The mount command allows us to mount a file system to the operating system.
The cd command allows us to change the working directory.
The sh command executes Standard Common Language (Shell) commands.
The shutdown command allows us to shutdown or restart the operating system.
The ls command prints the contents of any directory.
On Windows and macOS, install the VirtualBox hypervisor by downloading the installation files from the official website and following the instructions during installation. On Linux, however, install VirtualBox from the repositories of your distribution. On distributions based on Debian, we do this with the package manager "apt".
apt install virtualbox
After a successful installation, open VirtualBox and select New ... from the menu above to open the wizard for creating new virtual computers. In the first window, specify the Name, Machine folder, Type and Version of the new virtual computer. For example, we choose Debian as the name, /home/USER/VirtualBox VMs as the folder in which the virtual machine will be stored, Linux as the type, and Debian (64-bit) as the version. Then press the Next button.
In the second window, we determine the amount of memory (RAM) to be allocated to our virtual computer. For example, we specify 4096 MB of memory and press the Next button.
In the third window, we specify the virtual hard disk, namely, we can choose between three options: Do not add a virtual hard disk, Create a virtual hard disk now and Use an existing virtual hard disk file. For example, we choose to create a new virtual hard disk for our new virtual computer and press the Create button.
In the fourth window, we specify the format of the virtual hard disk that will be used by our virtual computer. We have three options: VDI (VirtualBox Disk Image), VHD (Virtual Hard Disk) and VMDK (Virtual Machine Disk) . For example, we select the VDI format and press the Next button.
In the fifth window, we define the method of allocating space for the virtual hard disk, which can be Dynamically allocated or Fixed size. For example, we select dynamic allocation and press the Next button.
In the sixth window, we specify where in the file system our new virtual hard disk will be created and what its maximum size will be. For example, we choose /home/USER/VirtualBox VMs/Debian/Debian.vdi for the location of our virtual disk and set its maximum size to 200.00 GB. Then click the Create button.
If we successfully created our Debian virtual machine, it appeared in the column on the left side of the VirtualBox window. In the column on the right side, detailed settings are displayed, which we specified during creation or were set to default values automatically.
Before the first launch, we can set the parameters of our virtual machine even more precisely by clicking on the Settings ... button in the menu above. For example, under the System\Processor tab, we can set the number of processor cores to assign to our virtual computer.
We have now finished setting up our new virtual machine and can start it by pressing the Start button. At the first start, a window will automatically appear for selecting the installation image of the operating system we want to install (e.g. Debian). The installation image of the operating system located on the disk can be selected by clicking on the button with the icon of the yellow folder with a green arrow. Otherwise, we can get to the selection of the installation image of the operating system if we go to the menu Devices\Optical drives\Select disk file... in the window of our virtual computer.
Now a bootloader window appears, in which we can choose between Graphical installation and Installation. For example, we decide on Graphical installation and press the Enter key on the keyboard.
In the next step, you can choose any language in which the installation will be performed. For example, select English or Slovenian and press the Continue button.
Now we choose where we are. For example, we get to Slovenia by selecting other\Europe\Slovenia and pressing the Continue button.
Then we select the localization. For example, we select United States - en_US.UTF-8 and press the Continue button.
Now let's choose the keyboard layout. For example, select Slovenian and press the Continue button.
In the next step, we define the name of our virtual computer. We can just use the default name debian and press the Continue button.
We can then select the network domain that our virtual machine will be a part of. We don't need it, for now, so we leave the field empty and press the Continue button.
Now enter any administrator password (root) in both fields and press the Continue button.
Next is the selection of the name of the new user, for which we can choose any name and press the Continue button.
Then we define any user name of the new user and press the Continue button.
In the end, enter any password of the new user in both fields and press the Continue button.
In the next step, we select the disks and set the partitions, where we can choose the default setting Guided - use entire disk, which will use the entire disk, and press the Continue button.
Now we select the disk on which we want to install our operating system. In our case, we select the only virtual disk we have and press the Continue button.
The following is the determination of the partitions on our disk, where one partition is sufficient for our needs, in which we save everything All files in one partition (recommended for new users) and press the Continue button.
Then the currently defined partitions that we will use and the option to manually set partitions are displayed. The default setting defines two partitions, namely: a primary partition for storing data with the EXT4 file system (Fourth extended file system) and a logical partition for expanding the system memory. We confirm the proposed partitions by selecting Finish partitioning and write changes to disk and press the Continue button.
Confirmation of the selected sections follows as the partitions and data that were previously written to the disk are deleted at this point. We select Yes to agree to the change and press the Continue button, thus starting the installation of the operating system.
During the installation, we refuse the installation of additional programs from other media by selecting the No option and pressing the Continue button.
Now we select the country in which we want to have a server that will be used by the package manager to install programs. A good practice is to select a country close to our location, for example, Slovenia and press the Continue button.
In the next step, we choose between the servers offered in the selected country for installing the programs. We can leave the default option deb.debian.org selected and press the Continue button.
The installation also allows us to set up a proxy server for Internet access, but we don't need it, so we leave the field empty and press the Continue button.
Next, disable the sending of anonymous data about our operating system used to the Debian servers by selecting the No option and pressing the Continue button.
In the next step, we select the graphical environment we want to use and possibly some additional software. For example, we will use the default values where we have the following options Debian desktop environment, GNOME and standard system utilities selected and then press the Continue button to continue the installation.
Now let's install the bootloader, which takes care of starting the operating system. We select the Yes option and press the Continue button.
Then select the disk on which to install the bootloader. We select our single installation disk by selecting /dev/sda (HARD_DISK_ID) and pressing the Continue button.
We have successfully installed the Debian operating system and now restart our virtual computer by pressing the Continue button.
After restarting, log into the operating system and test the operation of the operating system and the web.
In addition, we can also install VirtualBox Guest Additions, which allow us to automatically adjust the desktop resolution to the current window size, copy from a physical computer to a virtual computer and vice versa, and a bunch of other useful functionalities. We start the installation by updating the repositories of our operating system and then installing the packages we need before starting the installation.
su -
apt update
apt install build-essential dkms linux-headers-$(uname -r)
Now insert the VirtualBox Guest Additions installation image by selecting Devices\Insert Guest Additions CD Image ... in the virtual machine window. If we don't have the installation image yet, VirtualBox offers us to download it by confirming the download from the web by pressing the Download button twice and then the Insert button once more. If the automatic download does not succeeds, than manually download the right version of from this VirtualBox Guest Additions link.
In case of successful insertion of the VirtualBox Guest Additions installation image, we now have to mount it into the operating system.
mkdir -p /mnt/cdrom
mount /dev/cdrom /mnt/cdrom
cd /mnt/cdrom
Then we run the installation program and after successful installation, we restart our virtual computer.
sh ./VBoxLinuxAdditions.run --nox11
shutdown -r now
The easiest way to get a usable copy of a virtual computer is through the cloning process. We do it by right-clicking on the virtual computer in the left column of the main VirtualBox window to open an additional menu and click on the Clone ... option. A window for selecting cloning settings opens. You can specify Name, Path, MAC Address Policy and Additional options. MAC Address Policy allows us to Include all network adapter MAC addresses, Include only NAT network adapter MAC addresses or Generate new MAC addresses for all network adapters. For example, we choose Debian Clone as the name, we choose /home/USER/VirtualBox VMs as the folder where the virtual machine will be stored, we choose to create new MAC addresses for all network cards regardless of the settings and we leave the additional options unchecked. Press the Next button.
In the next step, we choose between the Full clone and Linked clone cloning modes. A full clone duplicates all of a virtual machine's files, while a linked clone keeps the same virtual machine files in shared files. The other files, which are different, are stored in files that are specific to each virtual computer. A linked clone takes up less disk space compared to a full clone. On the other hand, in a full clone, the clone provides faster access to files because they are written independently on the disk, while in a linked clone, several virtual machines access the same files on the disk at the same time, which can slow down access. Linked clones are dependent on each other, which can lead to unexpected changes in shared data and, as a result, corrupted files. In our example, we select the Full Clone option and press the Clone button to start cloning.
Below we present four possible network settings that at least partially allow us to connect via the network between several virtual computers.
Under the Network tab, we can assign up to four network adapters to our virtual computer. For example, we set the Adapter 1 of all our VMs to NAT, Internal Network, Bridged Adapter or NAT Network.
The NAT option sets us up to translate IP addresses from the network of our physical computer to the network of our virtual computer by changing the IP addresses in the IP packet headers (NAT - Network address translation ). In this case, our virtual computer has its network by default and cannot directly access other virtual computers, our physical computer and the physical network. Conditionally, we can provide access to specific applications by forwarding specific ports.
We set the network port forwarding by clicking on the Advanced tab and then clicking on the Port forwarding button.
Each port is forwarded by setting the Name, Protocol, Host IP, Host Port, Guest IP and Guest Port.
Accessing a virtual computer with a secure command shell (SSH) can be carried out via the NAT network by port forwarding. We install an SSH server on the virtual machine.
apt install openssh-server
We now forward the port by setting the Name to any name, Protocol to TCP, Host IP to the IP address of our physical computer, Host port to any port not used by other applications, such as 2222, Guest IP to the IP address of the virtual computer network adapter connected to the NAT network and Guest port to port 22, used by default by the SSH server.
We test the forwarded port by connecting from the physical computer's command line using SSH to the virtual machine and specifying the network port we forwarded on the physical computer, the user who will be used to log in to the virtual machine and the IP address of the physical computer.
ssh -p 2222 USER@IP_OF_THE_PHYSICAL_COMPUTER
The Internal network option connects several virtual computers to a network without a router, where they have to take care of establishing IP addresses themselves. The virtual computers can see each other after the network is set up correctly, but cannot access the web or other networks unless one virtual computer also acts as a router.
The IP address can be set on both virtual computers with the ip command, where we correctly set the IP address, network mask and network adapter to enable connectivity.
On the first virtual computer with the enp0s3 network adapter, set the network IP address for example to 192.168.1.1/24.
ip addr add 192.168.1.1/24 dev enp0s3
On the second virtual computer with the network adapter enp0s3, we set the network IP address in the same network as the first virtual computer, for example, to 192.168.1.2/24.
ip addr add 192.168.1.2/24 dev enp0s3
The Bridged adapter option enables us to share the network adapter of our physical computer with the virtual computer so that both obtain an IP address from the physical network. Our virtual machine acts as if it is connected to a physical network and by default has access to all computers on that network.
The option NAT network also sets up the translation of IP addresses from the network of our physical computer to a virtual network to which several virtual computers can connect. In this case, by default, our virtual computer has access to all virtual computers connected to the NAT network, which is defined by the name, but it does not have direct access via the network to our physical computer and the physical network. We can conditionally enable access to the physical network for certain applications by opening certain network ports (port forwarding).
If we select the NAT network option, this will not work for us by default, as we have to create it beforehand. We do this by selecting the File\Options ... menu in the main VirtualBox window. Under the Network tab, click on the button with the network adapter icon and the green plus symbol and create a new NAT network with the name NatNetwork.
The default values of the NAT network are sufficient for our needs, but we can change them by selecting the desired NAT network and clicking on the button with the network adapter icon and the orange gear symbol. We can also forward the ports for the entire NAT network. The selected NAT network can also be deleted by pressing the button with the network adapter icon and the red cross symbol.
If we use VirtualBox from version 7.0 onwards, then we manage the NAT network by selecting the menu File\Tools\Network Manager and then selecting the NAT Networks tab.
Now we can go back to the settings of our virtual machine by clicking on the Settings ... button in the menu above. Then, in the Network tab, we select that Adapter 1 uses the common NAT Network with the name NatNetwork that we previously created.
The IP addresses in individual virtual computers can be checked with the ip command.
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: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:40:07:ad brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic noprefixroute enp0s3
valid_lft 85104sec preferred_lft 85104sec
inet6 fe80::a00:27ff:fe40:7ad/64 scope link noprefixroute
valid_lft forever preferred_lft forever
The connectivity between individual virtual computers over the network can be checked with the ping command.
ping 10.0.2.15 -c 4
PING 10.0.2.15 (10.0.2.15) 56(84) bytes of data.
64 bytes from 10.0.2.15: icmp_seq=1 ttl=64 time=0.691 ms
64 bytes from 10.0.2.15: icmp_seq=2 ttl=64 time=1.44 ms
64 bytes from 10.0.2.15: icmp_seq=3 ttl=64 time=4.03 ms
64 bytes from 10.0.2.15: icmp_seq=4 ttl=64 time=0.538 ms
--- 10.0.2.15 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3027ms
rtt min/avg/max/mdev = 0.538/1.676/4.034/1.403 ms
