This seemed like a newbe question so I am placing it here.

I have a group that I create with groupadd. There is no corresponding user. I have added several users to the group by editing the /etc/group file so that it looks like:

<group>:x:527:<user1>,<user2>,<user3>,<user4>

I have a directory that is owned by root:root and has permission set 777. Inside this directory, I have a subdirectory owned by root:<group> with permission set as 770.

As <user3>, I can get to the first mentioned directory above, but can not get to the subdirectory. However, if I su, and then su <user3>, I can then get it.

What gives?

Please expand my understanding so I can correct this.

Thanks!

It sounds like you added user3 to the group and then immediately tried to access the directory. This doesn't work because user3 doesn't "realize" that he's in the new group yet. Log out and log back in as user3 and then try again. Also, it's probably a bad idea to make the top level directory 777, since that means anyone on the system can add or remove any file or directory to it. You should probably make it 755 or at least set the sticky bit (chmod u+t directory) to keep people from removing things that they don't own from it.