I'm putting (via curl on a client) a 10GB file up into an Apache server on Ubuntu Linux (v17.04). The root drive was pretty much full, and the ultimate destination for the PUT is a subversion root that is on a huge drive that's not root. The only other technology involved is mod_dav_svn.
How to move the tmp folder for Apache to that root drive too?
In modern Apache2 installs there's a /etc/apache2/envvars file that can happily have a line added to set the TMPDIR environmental variable.
Reboot Apache and it'll pick that up and run with it.
I've tested it over and over, and it works well (free space on the boot drive does not jeopardize the PUT of the large file).