Before upgrading any IP Office systems:
Plan for the upgrade.
Using the documentation for the target release, and any intermediate releases, understand any requirements created by changes in supported hardware, applications and system licensing requirements.
Verify the operation of the current system and obtain key details such as server addresses, passwords, etc.
Perform a full backup of all servers. Do not upgrade without having a backup of the existing systems. For information on backing up systems, see Backing Up IP Office Systems.
Perform the upgrade.
The first stage of any IP Office upgrade should be planning. You must consider and prepare for changes in supported hardware, applications and licenses. Each release of IP Office software is accompanied by a technical bulletin or release note which covers many of these issues.
These are available from the same support.avaya.com page as the downloads for the particular upgrade. You should obtain and read the technical bulletins for both the target release and also for any other intermediate releases that may have occured between that and your systems current release.
All major system changes, especially upgrades, should be preceeded by a full system backup. See Backup and Restore.
For 11.1, the underlying operating system used on Linux-based IP Office servers has changed from CentOS6 to CentOS7. Due to this, the normal upgrade methods cannot be used.
In order to upgrade to R11.1 from a pre-11.1 release, the Linux-based system must first be upgraded to R11.0.4.4. Once that has been done and operation of the system validated, a special upgrade process can be used to upgrade to R11.1.
The following links cover the normal upgrade methods that can be used for releases other than to 11.1 and for non-Linux-based IP Office servers.