How to upgrade Debian 9 to Debian 10 Buster using the CLI

Prerequisites

A system running Debian 9
A Debian user account with sudo privileges
Access to a command line/terminal window (Ctrl–Alt–F2)
A recent snapshot (backup) of the system

Upgrade to Debian Version 10 Buster

Make sure to bakup of Server data prior to upgrading. That way, if anything breaks during the upgrade, you can easily restore your system configuration.

Step 1: Update Package Manager and Repositories

By default, Debian 9 refers to the repositories designated for Stretch.

1. First, create a backup copy of the /etc/apt/sources.list file:

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

2. Then, open the file for editing

sudo nano /etc/apt/sources.list

3. Change all the references in this file from Stretch to Buster. The entries should appear as follows:

deb http://deb.debian.org/debian debian buster main

deb http://deb.debian.org/debian buster-updates main

deb http://deb.debian.org/debian buster/updates main

Debian Version 10 Buster successful install

4. Save the file using the keyboard combination Ctrl+O and Exit by pressing Ctrl+X.

Step 2: Upgrade from Debian 9 to Debian 10

1. Update the local package lists:

sudo apt-get update

2. Next, run updates on the software packages to prepare for the operating system upgrade:

sudo apt-get upgrade

3. Finally, run the distribution upgrade:

sudo apt-get dist-upgrade

4. Once the process completes, reboot the system to boot into Debian 10 Buster:

sudo reboot

Step 3: Verify Debian 10 Update

You can use the hostnamectl command to display the OS version with the command:

hostnamectl

The Operating System field should display Debian GNU/Linux 10 (buster).

The output should appear as:

PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

(Optional) Step 4: Remove Outdated Packages

After the upgrade to Debian 10, your system might have outdated packages and dependencies which are no longer necessary.

To remove outdated packages, run the --purge autoremove command:

sudo apt --purge autoremove

Conclusion

By following the directions above, you should have successfully upgraded from Debian 9 to Debian 10.

For more information about the upgrade process, including notes and extensive documentation, please refer to the Debian release notes.