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About Gabriel Canepa

Gabriel Canepa
Gabriel Canepa is a Linux Foundation Certified System Administrator (LFCS-1500-0576-0100) and web developer from Villa Mercedes, San Luis, Argentina. He works for a worldwide leading consumer product company and takes great pleasure in using FOSS tools to increase productivity in all areas of his daily work. When he's not typing commands or writing code or articles, he enjoys telling bedtime stories with his wife to his two little daughters and playing with them, the great pleasure of his life.

How to create, restore, and delete virtual machine snapshots in VirtualBox

This article is part of our Academy Course titled VirtualBox Tutorial: Virtualization Essentials.

In this course, we provide a compilation of VirtualBox tutorials that will help you get started with this virtualization platform. We cover a wide range of topics, from installing the software and performing a basic configuration, to cloning, exporting, importing, and removing virtual machines. With our straightforward tutorials, you will be able to get your own Virtual Machines up and running in minimum time. Check it out here!

In our previous article we discussed how to perform several operations with virtual machines including cloning, exporting, importing, and deleting appliances. Among other things, this allows us to back up our virtual machines and to distribute them in a single, bundled file. So far so good.

But what happens if you need to have restore points of your virtual machines you can roll back to in case something goes wrong or does not work as expected while you are making changes (or deploying code, to name another example)? The same principle applies when you want to go back to a given state of the appliance, and that is where snapshots come in handy.

In this tutorial we will explain what snapshots are, how taking a snapshot and restoring it is different than exporting and importing the virtual machine, and give a few suggestions to consider in order to effectively use them in your daily tasks.

Taking a snapshot

The very first difference between exporting a virtual machine and taking a snapshot is the fact that you can perform the latter operation regardless of the current status of the machine. You don’t necessarily have to shut it down in order to take a snapshot.

When you take a snapshot of a running appliance, the exact memory state is saved as well, along with the active processes. This may result in a security risk if you are logged on to that machine since restoring this snapshot will bypass the need to enter login credentials in order to use it. However, this may be what you want, so use it at your own discretion.

To begin, open VirtualBox and select the appliance which you want to take a snapshot of. Then click on the Snapshots button as illustrated in Fig. 1. The right pane will then display the list of snapshots that have been taken of that virtual machine (if any).

Figure 1: Switching to the Snapshots pane

Figure 1: Switching to the Snapshots pane

To create an initial snapshot, click on the camera icon shown in Fig. 1. You will then be prompted to choose a name for the snapshot and enter a brief description for it, as shown in Fig. 2. Then click OK.

Figure 2: Choosing a name and entering a description for the current snapshot

Figure 2: Choosing a name and entering a description for the current snapshot

It is a good idea to use the date when the snapshot was taken and another detail you choose. Again, write a description that is as detailed as possible in order to help you know which snapshot you should restore to go back to a specific point in time.

You should now see the snapshot in the list as shown in Fig. 3:

Figure 3: Listing virtual machine snapshots for the first time

Figure 3: Listing virtual machine snapshots for the first time

That said, let’s start the machine, make some changes (we will install the Apache web server as explained in “How to install the Apache web server (CentOS / Ubuntu Linux Installation)” using the terminal, which will create the corresponding configuration files as well). When we are done, Apache should be running and its configuration files present as shown in Figure 4.

Figure 4: Checking the status of Apache and configuration files after installation

Figure 4: Checking the status of Apache and configuration files after installation

Now let’s shut the machine down and take another snapshot as explained earlier.

Restoring snapshots

You should now have two snapshots of the appliance as seen on Fig. 5. Note how there are three buttons that are now enabled as compared to Figure 1.

Figure 5: Listing snapshots after creating a second one

Figure 5: Listing snapshots after creating a second one

Pay special attention to the highlighted buttons in Fig. 5:

  1. Restore the selected snapshot.
  2. Delete the selected snapshot.
  3. Display a window with information about the selected snapshot.

Once we have made sure the first snapshot is selected, let’s click on the button indicated as #1 above. You will be prompted to confirm the restoration. Choose Restore in the popup window that will appear (see Fig. 6 for more details).

Figure 6: Confirm before restoring the snapshot

Figure 6: Confirm before restoring the snapshot

Then let’s start it and check that Apache and its configuration files are not present. The output should be as shown in Fig. 7:

Figure 7: Checking the status after restoring the virtual machine to a previous snapshot

Figure 7: Checking the status after restoring the virtual machine to a previous snapshot

As a personal exercise, you can turn off the appliance and restore the second snapshot. You should then be able to use Apache again. As you create and restore snapshots, pay attention that this process is generally a faster solution than exporting and importing an entire virtual machine.

Things to consider when restoring a snapshot

You have now learned how to create snapshots and how to restore them. It is a good time to point a few important facts you need to consider:

  • The hardware settings of the virtual machine are restored as well. If you had assigned more memory, for example, restoring a previous snapshot will undo this change.
  • As for modifications made to files, keep in mind that files previously created will be gone, files that had been deleted will be restored, and any changes to existing files will be reverted.
  • The snapshots are stored as .vdi (virtual drive) files in a folder named Snapshots under the same directory where the virtual machine files are kept (you can browse directly to this directory by right-clicking on the appliance and choosing Show in File Manager from the popup menu).

You may need to pay special attention to the last item in the list above, as carelessly creating snapshots will result in filling up storage space that may be needed for something else. Make sure to check the snapshots regularly and delete the ones you don’t need anymore.

Summary

In this tutorial we have discussed what virtual machine snapshots are, and explained how to create, restore, and delete them. You are in a better position to operate your appliance now, as you can create restore points to roll it back to a specific state or point in time.

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