This guide assumes that you have a system running Ubuntu 15.10, configured with a non-root user with privileges for administrative tasks.
Please note that if a new kernel is installed while running the above command, you need to reboot system in order to continue the upgrade process.
Then open Software & Updates from Unity Dash or your favorite application menu.
See How To Use Digital Ocean Snapshots to Automatically Backup your Droplets for more details on the snapshot process.
When you have verified that the update was successful, you can delete the snapshot so that you will no longer be charged for it.
To check your Ubuntu version, run If you are running Ubuntu 17.04, then follow the on-screen instruction to upgrade to Ubuntu 17.10.
If you are running Ubuntu 16.04, then follow the on-screen instruction to upgrade to Ubuntu 17.04 first and then follow the same steps to upgrade to Ubuntu 17.10.
Comprehensive backups and extensive testing are strongly advised.
To avoid these problems, when possible, we recommend migrating to a fresh Ubuntu 16.04 server rather than upgrading in-place.
Update: Ubuntu 17.04 reached end-of-life on January 13, 2018.
Ubuntu 16.04 users can now upgrade directly to Ubuntu 17.10.
Failing that, ensure that you have copies of user home directories, any custom configuration files, and data stored by services such as relational databases.