Ewww could not install the tools in wp-content/ewww/

what OS are you running now? What were you running before?

I was on ubuntu with nginx, now I am on CentOS with nginx.

Check the permissions on that folder, the web user (likely httpd) needs to be able to write to the wp-content/ewww/ folder. Moving files from one linux box to another may have also messed up the ownership of the files as well, so make sure your wordpress folder has the right ownership (and apply it recursively).

that folder has drwxrwxrwx. And all the files inside have:

-rwxrwxrwx 1     33     33 337170 Mar 10 11:16 cwebp
-rwxrwxrwx 1     33     33 342379 Mar 10 11:16 cwebp-alt
-rwxrwxrwx 1     33     33 294779 Aug 26  2014 cwebp-custom
-rwxrwxrwx 1     33     33 750042 Aug 26  2014 gifsicle
-rwxrwxrwx 1     33     33 120094 Mar 10 11:16 jpegtran
-rwxr-xr-x 1 apache apache 102000 Mar 10 11:16 jpegtran-alt
-rwxrwxrwx 1     33     33 742965 Aug 26  2014 optipng
-rwxrwxrwx 1     33     33 838189 Aug 26  2014 pngquant

who is the owner of the ewww folder? 33:33 indicates the user id from the ubuntu server. You should make the entire wordpress folder owned by apache:apache like so:

chown -R apache:apache /var/path-to-wordpress-root/

Hi, done. Now all the www sites are owned by the web server.
There are still the same issues with the library and with that error message.

I tried to turn off and turn on the plugin, but the same.
I also turned on the plugin debug and I can see this: https://pastebin.com/ddYJRkQa

I a new log. Now it’s much bigger with more info. I replaced the name of the site with “mysite”: https://gist.githubusercontent.com/utnalove/c915fe3a70ad077989ae/raw/dbg%20ew3

how about just the debug information from the settings page, that would be helpful

If you mean the debug log from here: wp-admin/options-general.php?page=ewww-image-optimizer/ewww-image-optimizer.php#, this is the one I put githubusercontent.com, because pastebin does not support so big texts

I also tried to generate a wordpress debug with:

define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);

But it’s not generating any debug file, for some reason ??

Got it. Sorry, I didn’t notice there is an html version of the bug in the settings page. Here it is: https://pastebin.com/HdmUm8aU

Try setting permissions to 755 on everything in the ewww/ folder.

Done, now the files have -rwxr-xr-x
It looks like the error message disappeared. The new debug is here: https://pastebin.com/e7meH3bh

And the library is working fine now. Why with 777, which is a higher permission didn’t work?

Do you see any other problems in the debug log?

It doesn’t work with 777 because the plugin checks specifically for 755. I suppose I could probably change that, but the permissions check is a bit odd to start with. It’s not as simple as just looking for ‘755’ or ‘777’, it has some weird encoding issues.

Thank you. I see I have to check back all the permissions of the /var/www.
The wordpress debug.log is not being generated in the wp-content folder. Probably it’s another permission issue ??