I just dropped
putenv('TMPDIR=/data/xerte');
into modules/xerte/export.php
and hey presto
2015-10-12 10:14:55 /srv/www/vhosts/xerte/xertetoolkits/modules/xerte/export.php112Temporary zip file is : /tmp/xerteExportFEdO0Y
went to
2015-10-12 10:27:35 /srv/www/vhosts/xerte/xertetoolkits/modules/xerte/export.php112Temporary zip file is : /data/xerte/xerteExport793mcg
however the change of TMPDIR does not appear to be set in env
# env | grep TMP
# env | grep TMPDIR
For future releases would it be possible to make the directory where the zip is created a variable that can be configured via the admin UI