Temporary Directory
Explanation
The temporary directory is where XWiki puts data it can produce again: resized images, attachments extracted from the database in order to be processed, and the intermediate files of operations such as an export. XWiki empties it at every startup, so nothing may be stored there that anything else depends on.
XWiki does not write straight into the directory the servlet container offers. It uses an xwiki-temp sub-directory of the location the container publishes as jakarta.servlet.context.tempdir, and it needs write access to it. When that location is missing or not writable, XWiki falls back to the directory named by the java.io.tmpdir Java system property; when that one is not writable either, it fails to start.
This is also where a permanent directory that was never configured ends up, which is how data that must be kept can disappear at the next restart.
FAQ
Do all parts of a running XWiki use this directory?
No. XWiki and its own components do, while third-party libraries usually write to the directory named by the java.io.tmpdir Java system property, which is not necessarily the same place.
