The coronavirus situation made a dedicated DESY-wide messaging (chat) service more important. As a result, Mattermost was initially made available temporarily starting April 15, 2020, following a decision by the DESY Directorate.

The re-evaluation in light of the expiration of the current Mattermost licenses at the end of April 2026 confirmed a continued need for a messaging service. Given the changed licensing terms and costs for Mattermost, we cannot continue using it. Therefore, after analyzing available options, we are switching to Nextcloud/Talk and integrating the messaging service into our storage cloud Sync&Share (sas.desy.de).

The migration to Nextcloud Talk is currently planned for mid-April. The procedure and associated measures are outlined below.

Preparatory measures for the migration

The migration of data from Mattermost to Nextcloud Talk is handled centrally by DESY-IT. No special preparations or precautions are required on the part of users. However, if you have channels that should not be migrated, please archive them before the migration begins.

Channels can only be archived by the channel administrators. To do this, open the relevant channel and click on its title at the top. In the context menu, you should see the "Archive Channel" option at the very bottom.

Migration process

1. Shortly before the migration begins, all DESY users will be centrally granted access permissions for Nextcloud Talk (resource "sas-talk").
2. According to the current plan, the migration will be completed within a single weekend.
3. After the migration, access to Mattermost will no longer be possible as currently planned.
    

Are follow-up tasks required?

The following minor follow-up tasks may be recommended depending on your personal settings needs:

• Personal profile settings may need to be adjusted (e.g., setting a profile picture).
• Favorites need to be reconfigured.

Normally, no follow-up tasks are required. The following follow-up tasks may be necessary in special cases:

• Channels that were publicly accessible across DESY in Mattermost will be private after the migration. If the conversation should remain visible across DESY after the migration, this must be adjusted in the conversation settings after the migration. Please see here for further instructions.
• For (very few) channels that no longer have an admin, an admin will be randomly assigned. After the migration, it should be checked whether this arrangement should remain.
   

For more information on technical details and further instructions on recommended actions after the migration, click here.

What is different in Nextcloud Talk compared to Mattermost?

You can find an overview of the key changes/differences here.