Before I say anything, I know how permission for groups and users works.

My setup is:

a. my user is monkey and is in the group www-data

groups monkey

monkey : monkey adm cdrom sudo dip www-data plugdev lpadmin sambashare

b. the root folder of apache is /home/monkey/var/www and has the permissions 0775 with owner www-data and group www-data

ls -la /home/monkey/var/www

total 8
drwxrwxr-x 2 www-data www-data 4096 Aug 12 10:37 .
drwxr-xr-x 3 root root 4096 Aug 12 10:37 ..

c. But I'm unable to write in /home/monkey/var/www/

monkey@ubuntu:~$ cp robots.txt var/www/robots.txt

cp: cannot create regular file âvar/www/robots.txtâ: Permission denied

The robots.txt file was created under monkey user.

What am I missing?