This article requires more details with links to the other upgrade options. Maybe even have a general intro page on updates. Also, the same steps to record the Ubuntu version information before running the update.
In a server environment there are different levels of updates,
- upgrade - Package Update without removing packages
- dist-upgrade - Package Update using conflict resolution to remove outdated packages
- do-release-update - Release Updates
This is to allow the administer fine grained control. The more higher level of updates, the more risk to a system.
After running an upgrade, ssh into the system with a new session and check if the system welcome message requests a reboot,
sudo reboot
upgrade
Package Update using upgrade is the safest and covered in Setup Ubuntu Linux Base Server. The command to upgrade is,
sudo apt-get upgrade
A reboot is almost never required.
From the man pages,
dist-upgrade in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt-get has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist-upgrade command may remove some packages. The /etc/apt/sources.list file contains a list of locations from which to retrieve desired package files. See also apt_preferences(5) for a mechanism for overriding the general settings for individual packages.
Once the system actually is in production you will want to review what will be upgraded before actually performing the upgrade. This can be performed using --simulate,
sudo apt-get upgrade --simulate
dist-upgrade
The next level is,
sudo apt-get dist-upgrade
This type of upgrade often updates the Linux headers. A reboot is sometimes required.
From the man pages,
dist-upgrade in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt-get has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist-upgrade command may remove some packages. The /etc/apt/sources.list file contains a list of locations from which to retrieve desired package files. See also apt_preferences(5) for a mechanism for overriding the general settings for individual packages.
do-release-update
Release updates are the most disruptive. The almost always require a reboot. The process is quite involved and it is recommended to turn off all services.