On 4/10/2018 7:32 AM, Christopher Schultz wrote:
What happened is that the new core directory was created as root,
owned by root.
Was it? If my server is running as solr, how can it create directories
as root?

Unless you run Solr in cloud mode (which means using zookeeper), the server cannot create the core directories itself. When running in standalone mode, the core directory is created by the bin/solr program doing the "create" -- which was running as root.  I know that because you needed the "-force" option.  So the core directory and its "conf" subdirectory (with the config) are created by the script, then Solr is asked (using the CoreAdmin API via http) to add that core.  It can't, because the new directory was created by root, and Solr can't write the core.properties file that defines the core for Solr.

When running Solr in cloud mode, the configs are in zookeeper, so the create command on the script doesn't have to make the core directory in order for Solr to find the configuration.  It can simply upload the config to zookeeper and then tell Solr to create the collection, and Solr will do so, locating the configuration in ZooKeeper.

See the big warning in the CREATE section of the CoreAdmin API documentation about the CREATE action needing to be able to find a configuration:


You might be wondering why Solr can't create the core directories itself using the CoreAdmin API except in cloud mode.  This is because the CoreAdmin API is *OLD* and its functionality has not really changed since it was created.  Historically, it was only designed to add a core that had already been created.  We probably need to "fix" this ... but it has never been a priority.  There are bigger problems and features to work on.  Cloud mode is much newer, and although the Collections API does utilize the CoreAdmin API behind the scenes, the user typically doesn't use CoreAdmin directly in cloud mode.

The client may be running as root, but the server is running as 'solr'.
And the error occurs on the server, not the client. So, what's really
going on, here?

I hope I've explained that clearly above.


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