Drush won't clear uploaded temporary files So, working on a unix system, it's common that /tmp has the sticky bit set (i.e. only the owner of the temporary file can write/delete it). This is an issue when running drush cron.

If I upload a file, and the file gets stored in /tmp, then the owner is _www (I'm on a MacOS machine). When I run drush, I'm running it as my own user, so if I run drush cron then my user is attempting to delete the temporary file(s) that was uploaded, and I get a permission denied.

Can anyone think of a simple workaround for this problem?
Simply make CRON run drush as _www user. /etc/cron.d suppotys it, it's format is:

#&lt;timing&gt;   &lt;user&gt; &lt;command&gt;


Just make entry for your drush:

11 * * * *    _www   drush


Details, of course, may vary a little.

I used this answer.