How do I backup a nexus repository manager
The nexus book: http://www.sonatype.com/books/nexus-book/reference/. Does not seem to spend any time on how one should go about backing up a nexus repository. If I am installing my snapshot and releases into this local repository, it seems that it would behoove me to back it up. However, I'm not really interested in backing up anything that can easily be downloaded from a remote repository.
Some google searches do not seem to reveal the canonical answer either, so perhaps for posterity it can be recorded here.
Thanks, Nathan
Answer
When you install Nexus, you'll end up with two directories:
nexus-webapp-1.3.1.1/
sonatype-work/
We've separated the application from the data and configuration. The Nexus application is in nexus-webapp-1.3.1.1/ and the data and configuration is in sonatype-work/nexus. This was mainly done to facilitate easier upgrades, but it also has the side-effect of making it very easy to backup a Nexus installation.
The Simple Answer
Nexus doesn't store repositories in a database or do anything that would preclude a simple backup of the file system under sonatype-work/nexus. If you need to create a complete backup, just archive the contents of the sonatype-work/nexus.
Better Answer
If you want a more intelligent approach to backing up a Nexus installation, you will certainly want to backup everything under sonatype-work/nexus/conf, sonatype-work/nexus/storage, sonatype-work/nexus/template-store. If you want to backup the metadata and file attributes that Nexus keeps for proxy repository, backup sonatype-work/nexus/proxy, although this isn't required as the information about the proxy repository will be generated on-demand as attributes are requested.
You don't need to backup sonatype-work/nexus/logs and you don't need to backup the Lucene indexes in sonatype-work/nexus/indexer.
Nexus Pro Answer
There is a Nexus Professional plugin which can automate the process of creating a backup of the Nexus configuration data. This plugin is going to address the contents of the sonatype-work/nexus/conf directory. If you need to backup the sonatype-work/nexus/storage directory, you will need to configure some backup system to backup the contents of that filesystem. Once again, as with Nexus Open Source, there is currently no real benefit in backing up the contents of sonatype-work/nexus/indexer or sonatype-work/nexus/logs.
Excluding Storage for Remote Repositories
In your question you mention that you want to exclude the storage devoted to the local cache of a remote repository. If you are interested in doing this, you'll have to take a further level of granularity and just exclude the directories under sonatype-work/nexus/storage that correspond to the remote repositories.
Do you need to shut Nexus down for a backup?
Brian Fox told me no, the only real chance for file contention is going to be the files in the indexer/ directory. You shouldn't have a problem backing up the sonatype-work filesystem with a running instance of Nexus.
BTW, thanks for the question, this answer will likely be incorporated into the next version of the Nexus book.