Wordpress can't find temporary folder, but folder it's looking at has correct permissions

Question

So, I've spent a couple of hours looking around the internet to try to figure out this problem, since it seems like a dumb one that would probably be a duplicate, but apparently it isn't.

I'm hosting a WordPress site in a subdirectory on my main site (http://christopherdumas.org is the main site, http://christopherdumas.org/astraterra is the WP site) and when I try to upload files to a post in the WordPress site, it smacks me with this error:

Missing a temporary folder.

Now, this was working before I upgraded to WP 5.0, and I didn't test it after the update, assuming that it would just continue to work. It didn't. I thought I'd done everything necessary for the PHP server and WordPress setup to persist on boot, but I recently restarted my server and I had to restart/fix a couple things with WP so apparently not-- which might have something to do with this issue. Interestingly, I did the normal path to fix this the first time this happened, and I think that fixed it but I don't clearly remember, and now I'm having that problem again, even with the "fixed" configs.

Even worse, adding the usual lines to my wp-config.php file (setting WP_TEMP_DIR, etc) isn't helping, and neither does editing my php.ini (in the root directory of the server). Furthermore, the temp directory has www-data permissions (as does the entire wp-content directory) and I added a bit to the beginning of index.php to make sure that it is using www-data as the user, which it is. At this point, I can't think of anything more to do. I'm running this server on top of Lighttpd instead of Apache 2, which I did originally because of Lighttpd's ease of use, but I'm starting to regret doing that...

Answer 1

Connect to your server via SSH.

and remove System temporaty files:

rm -rf /tmp/*

Delete files that are older than 12 days from the /tmp and /var/tmp/ directories:

find /tmp -type f -mtime +12 -exec rm {} \;
find /var/tmp -type f -mtime +12 -exec rm {} \;

Delete temporary files created by Plesk and its services. Files in the directories below can be safely removed.

Note: We recommend to run these commands when the system is idle (No active Plesk backup and Plesk Installer tasks).

To check if Plesk Installer is running, run the following command:

ps aux | grep install | grep -v "grep"

No output means Plesk Installer is inactive.

To check if any Plesk backup task is running, run the following command:

plesk sbin pmmcli --get-tasks-list Backup | grep working

No output means there are no active backup tasks.

Temporary Plesk backup files:

rm -rf /usr/local/psa/PMM/tmp/*

Other temporary files:

rm -rf /usr/local/psa/tmp/*

If that does not work restart your apache.