/sitemap.xml doesn't appear
No. That file is task code and should execute as expected. It did if you went to the tasklog and saw a message the sitemap file was not writable. The problem appears that your webserver is not executing as Owner or User which has a 7 (read, write, execute) permission. It is either operating as member of Group or as Other both of which have a 5 (read, execute) permission. Specifically 5 does not permit writing.
You said you met with success with permission of 777, which some would agree is not necessary because it permits wide open permissions. 7 in all 3 positions is read, write and execute for anybody.
So, you could try 765. If that works, then httpd is operating as member of the group and 6 allows read and write. If 765 doesn't work but 756 does, then PHP is operating as Other because you gave it read and write permissions. There should be no need for execute permission to be given.
If 765 or 756 do not work, try 775 or 757. When you do get satisfactory results, that will tell you what your server's PHP is running under. As a consideration for others who stumble upon the same problem, report back with what you did to get success with this problem.
There is a possibility that something else is causing this problem, but the fact you met with success using 777 says it's only a permissions problem. Crazycat gave you the answer. My suggestion is to try the entire combination one by one until you find the right one.
You said you met with success with permission of 777, which some would agree is not necessary because it permits wide open permissions. 7 in all 3 positions is read, write and execute for anybody.
So, you could try 765. If that works, then httpd is operating as member of the group and 6 allows read and write. If 765 doesn't work but 756 does, then PHP is operating as Other because you gave it read and write permissions. There should be no need for execute permission to be given.
If 765 or 756 do not work, try 775 or 757. When you do get satisfactory results, that will tell you what your server's PHP is running under. As a consideration for others who stumble upon the same problem, report back with what you did to get success with this problem.
There is a possibility that something else is causing this problem, but the fact you met with success using 777 says it's only a permissions problem. Crazycat gave you the answer. My suggestion is to try the entire combination one by one until you find the right one.
