In this article I will provide simple instructions on how to upgrade Ubuntu 12.04 to 14.04.
In fact I didn't wanted to push for a server upgrade for a while, but decided to do it now, and not to wait when things will break completely. In fact I was working on a Drupal 8 site development and wanted to have it on more recent version of server, and so I opted to upgrade whole server. Following tutorial is inspired from How to Upgrade to Ubuntu 14.04 LTS
Backups
I highly suggest you to take a snapshot of your current server, before pushing for your upgrade. I have Linode backups enabled and before proceeding further I took a snapshot. It was pretty fast less than 5 minutes to generate a backup for all of mine server.
Stopping services
It's recommended that you stop as many services as possible before upgrading to Ubuntu 14.04 LTS. This includes web server daemons (Apache and nginx), database servers (PostgreSQL and MySQL), and any other non-critical services.
sudo service nginx stop
I opted to stop nginx
Upgrade your Linode to Ubuntu 14.04 LTS by entering the following command:
sudo do-release-upgrade -d
Follow the on-screen instructions to complete the installation process.
Because Linode offers internal package mirrors for Ubuntu, you may see this message:
No valid mirror found While scanning your repository information no mirror entry for the upgrade was found. This can happen if you run an internal mirror or if the mirror information is out of date. Do you want to rewrite your 'sources.list' file anyway? If you choose 'Yes' here it will update all 'precise' to 'trusty' entries. If you select 'No' the upgrade will cancel. Continue [yN]
Type y and return to continue.
The upgrade will cause your Linode to reboot. After it does so, verify that it’s running Ubuntu 14.04 LTS by entering the following command: cat /etc/lsb-release
You should see output that resembles the following:
DISTRIB_ID=Ubuntu DISTRIB_RELEASE=14.04 DISTRIB_CODENAME=trusty DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
Your Linode is now running Ubuntu 14.04 LTS.