I have added debian8 into group www-data with command .

```
sudo usermod -G www-data  debian8

```

It can be verified with command.

```
cat /etc/group |grep 'www-data'
www-data:x:33:debian8

```

The ownership properties:

```
-rw-r--r-- 1 www-data www-data 418 Sep 25  2013 /var/www/html/wp/index.php

sudo ls  -al  /var/www/html/wp
total 200
drwxrwxr--  5 www-data www-data  4096 Jan  5 10:16 .
drwxrwxrwx  5 www-data www-data  4096 Jan  4 15:51 ..
-rw-r--r--  1 www-data www-data   418 Sep 25  2013 index.php

```

Why debian8 as a member of group www-data can't cat it?

```
debian8@hwy:/var/www/html/wp$ cat index.php
cat: index.php: Permission denied

sudo getfacl /var/www/html/wp/index.php
getfacl: Removing leading '/' from absolute path names
# file: var/www/html/wp/index.php
# owner: www-data
# group: www-data
user::rw-
group::r--
other::r--

```

Do as heemayl say,**Logout and then login**,the file `/var/www/html/wp/index.php` can be cated,why can't touch a new file in `/var/www/html/wp/test.txt` now?

```
touch  /var/www/html/wp/test.txt
touch: cannot touch ‘/var/www/html/wp/test.txt’: Permission denied

```

[![enter image description here](https://i.stack.imgur.com/WEWVO.png)](https://i.stack.imgur.com/WEWVO.png)

It is so strange that 

no problem for

```
touch  /var/www/html/wp/test1.txt

```

no permission for 

```
touch  /var/www/html/wp/test.txt

```