How do I back up files from a My Cloud v5.12.108 to v4.05.00-342 system?

How do I back up files from a My Cloud v5.12.108 to v4.05.00-342 system? I have two 4TB My Cloud NAS drives on the same network, but one is an older version and won’t run the new OS5. I would like to run something on the OS5 unit, so that I don’t need to involve an external computer in the transfer.

If you cannot do it using the Apps (Local Backup app or Remote Backup app) in the My Cloud Dashboard then you may need to rely on using Rsync via SSH to copy files to the first gen single bay v4.x firmware My Cloud.

How to Create a Remote Backup on a My Cloud Device
https://support-en.wd.com/app/answers/detail/a_id/19931

My Cloud OS 5: Remote Backups
https://support-en.wd.com/app/answers/detail/a_id/30036

There are a number of discussions on using Rsync to copy from an OS3 version single bay My Cloud to another location. It is possible one of those discussions will give you hints on how to proceed on OS 5 to copy the contents from an OS 5 My Cloud to a first gen single bay v4.x firmware My Cloud.

https://community.wd.com/search?q=rsync%20category%3A105

Thank you.
I have to check if my router uses uPnP and if it is enabled.
I would like to ask if the change to a static IP can be left in place and how one determines a good static IP to use.

Not sure UPnP even matters if one has both My Cloud devices on the same local network.

If both My Cloud devices are on the same local network then there is usually no need to change IP address’s on them. The Remote Backup directions link may be for backing up one My Cloud to another located on a different network.

One of those WD links above indicates that apparently Remote Backup app doesn’t support v4.x firmware single bay My Cloud devices.