In Nexus 2 you can copy the sonatype-work directory between instances. However, the repositories are stored differently in Nexus 3 and it is no longer possible to move the folders.
When migrating to Talend 7.x.x from any earlier version you will have Nexus 2. However, you want to be on the latest supported version of Nexus.
Upgrade the current 2.x version to 2.14.9, the latest release of Nexus 2, and then you can migrate from 2.14.9 to 3.9. You can download version 2.14.9 from the Sonatype site.
To upgrade your Nexus, overwrite your Nexus folder, in this example, /talend/tac/nexus/nexus-2.14.3-02, with the new version folder. However, you may need to fix the service.
Keep both Nexus sites for 2.14.9 and 3.9 are up, and make sure they do not share the same operating port, or they will collide. Locate the configuration file for both 2.x and 3.x versions, for example:
In 3.x, 7.x.x\tac\Artifact-Repository-Nexus-3.9.0-01-win64\sonatype-work\nexus3\etc\nexus.properties
In 2.x, 6.x.x\tac\Artifact-Repository-Nexus-V2.14.3-02\nexus-2.14.3-02\conf\nexus.properties
Login using the default admin credentials:
Enable the Upgrade: Agent capabilities in the 2.14.9 version of Nexus:
From the Nexus 3.9 UI, delete all of the repositories that you want to import. Navigate to Capabilities and activate the Upgrade tab on the Preferences screen.
Then you will be able to point to the Endpoint and the access token that you get from Nexus 2.14.9 to complete the migration.
For more information on the steps post upgrade to 2.14.9, watch the Sonatype, Easy upgrade to Nexus Repository 3 video.
You can find a great video tutorial here: 3:19 Internal Video with Talend Repos. At the end of the video, select Continue on your systems and complete the migration.
If when copying over the Nexus folder to upgrade from 2.x version to 2.14.9 your OS says the path is too long, simply move the artifact Nexus installation folder to the C or C:/talend drive.
If you start the migration process and you are not able to check any of the repository boxes then you have to first delete the Talend Specific Repositories from Nexus 3.9 before the migration can begin.