group permissions on directory being ignored for group member

[Itamar Gal]

Hey Ubuntu users,

Some quick background about me. I'm a junior sysadmin in a firm whose IT
department has no senior sysadmins, and I'm relatively new to the job. I've
inherited an environment from a previous administrator who was much better
at his job than I am, but who didn't leave much in the way of documentation.

Recently we've been experiencing a seemingly bizarre issue where it seems
that there is a user (on an Ubuntu 12.04.4 server) who is unable to access
a shared directory, even though that user belongs to the group which owns
the directory. Here is an example session:

$ whoami
username

$ cd /shared_directory
bash: cd: /shared_directory: Permission denied

ls /directory
ls: cannot open directory /shared_directory: Permission denied

$ ls -ld /shared_directory
drwxrws---+ 116 root groupname 4096 Jun 11 11:35 /shared_directory

$ getent group groupname
groupname:*:username:otheruser

sudo adduser username groupname
The user `username' is already a member of `groupname'

I posted this question on ServerFault here:

http://serverfault.com/questions/705988/group-permissions-on-directory-being-ignored-for-user

but I haven't gotten any responses.

A few remarks are probably in order. We are using LDAP-based authentication
which inherits from a global LDAP server run outside of our department. We
have a script which imports user data from the global LDAP server to our
own LDAP server.

This permissions issue has happened a handful of times so far. Each time I
was able to fix the problem by manually removing the user account form our
LDAP server and then reimporting the account from the global server
(although I have no idea why this had any effect, as I couldn't see any
differences in the relevant LDAP entries). But now I've run into a case
where doing this didn't resolve the problem, so I probably have to figure
what's actually going on.

If anyone can shed any light on this I would be forever indebted to you, as
I am completely baffled by this.

Cheers,
Itamar
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