This update (Debian 10) dates back to July 6, 2019. It is important to note: in order for the update to succeed, all commands must be run as root. Otherwise, you will need to add sudo.

Preparation

The important point is that you need to backup your virtual server. On its own, Debian is very stable; but there is always a degree of probability that potential incompatibility will arise.
Still important is the presence of broken packages. This can be done with dpkg –audit. If this does not help, you can try to fix the problem with apt -f install or dpkg –configure -a. In the case of faulty dependencies that cannot be resolved, aptitude -f install may fix it.

Also, you should make sure that the kernel metapackage is installed, which is similar to linux-image-amd64. If you have only the linux-image-4.9.0-9-amd64 package installed, your kernel may not be updated as needed. You can verify that it is installed by running apt install linux-image-amd64.

Updating all current packages

All packages must be updated to the latest version before updating the release. This is necessary in order to minimize all possible problems.

apt update
apt upgrade
apt autoremove --purge
reboot

Modifying Package Lists

Next, all package lists should be updated from Stretch to Buster. You can do this manually using the following:

nano /etc/apt/sources.list /etc/apt/sources.list.d/*

Upgrading to Debian 10

First you need to update the list of packages Debian 10

apt update

Next, update the packages themselves:

apt upgrade
apt dist-upgrade

During the upgrade, you may be asked if you want to restart the services. You can safely say no, as you will reboot later.

After which, you can reboot

reboot

Cleanup

It is necessary to make sure that your server has been updated when you started lsb_release -a. The conclusion should look like this.

No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 10 (buster)
Release:        10
Codename:       buster

You can remove any remaining dependencies with apt autoremove --purge.