I would replicate all the dbs.   This way the views will get rebuilt,  Daos will start fresh.     If you are changing ips  on the new server don't forget to change dns. server docs and connections docs.  If you can get by not doing that and going with the old server1 ip address even better.

I'm with Barry, definitely replicate the databases and it won't take that much longer replicating than copying via OS + the domino will accept the databases better so no risk of consistency checks or corruptions. A "pull" is quicker then a push so trigger the replication from Server1 so that it pulls from Server2.

Also note Barry'ssuggestions if it's a different IP from Server1 to the new Ubuntu server - make those changes on Server2's domino if required.

No need to remove Server1 from CLUSTER either I wouldn't have thought since you are going to bring it back up on the new Ubuntu server.

I would say, you're trying to set up a block-cutover type of installation.

Take your time, set up the Linux server.

Replicate everything over. Do it early. Why not, you'll be able to replicate again to sync up what's happened since.

If everything goes down, you get to recover without rewriting.

Copying (I assume you mean OS-level copying) won't let you resync this way, and frankly I don't know, is the Linux ODS now identical to the Windows ODS?

I'm sure you meant OS-level, but if you didn't, Notes copies change the DBID: you'll always have more options with replicas, and your users and their DBLinks and doclinks all continue to work.

There's just nothing better.

Replicate.

Thanks for all your answers.

The main issue here is that I need to maintain the original server name, in the new server.

So, original domino server name: SERVER1, new linux domino server name: SERVER-LINUX. Then I can replicate, but when replication finishes, I don't if the domino server can just be renamed, so, to take down SERVER1, and user SERVER1 in the new linux box.

Another way would be to replicate all to a temp server, lets say SERVER-TEMP, and when all DB are replicated shut the original server down, and configure a new one with the original name, and replicate back from TEMP. But this wouldn't be an online OS migration..

There are a handful of knowledge center articles I've seen over the years - take a look here:

https://www.ibm.com/support/knowledgecenter/SSKTMJ_9.0.1/admin/admn_reinstallingormovingadominoserverfromonecomputer_t.html

If Server1 has a large amount of data, you may want to not put Server2 into a cluster until you have finished replication of all applications from Server1 to Server2. If, for some reason, Server1 should fail, your users may be upset to find incomplete data (incomplete replicas or missing replicas) on Server2. My procedure is to add Server2 to the cluster only when everything appears to be in sync. 

Regarding Mike's question about whether the ODS in Linux is now the same as the ODS in Windows, I can't say. I have done an OS-level copy of data in both directions simply to check this, and I've not encountered obvious data corruption issues. However, I defer to others on whether this is supported, and I avoid relying on an OS-level copy from Windows to Linux or from Linux to Windows.   

Thanks guys.

The link Mark provided informs of a procedure to migrate from one OS to another. They don't mention anything about incompatibilities between OS for certain domino files: they do suggest to do an FTP-copy instead a direct OS-copy, to avoid problems with codepages corruption in some cases.

Thanks Jay for the suggestion about enabling clustering after replication, it is indeed a logical one.

Some weekend will migrate to linux and report back.