Hofmockel.org

Installing an access control module removes the default "grant all" entry in node_access table. Uninstalling or disabling the module doesn't neccessary return the the default "grant all" privilege.

run the SQL code below to return the entry.

INSERT INTO node_access VALUES (0, 0, 'all', 1, 0, 0);

ref: http://drupal.org/node/12757#comment-42578

symptom: Granted edit permissions to a user but they can not edit the node.

solution: If the user's role does not have the permission to use the
"input type" the node is submitted as, they will not be allowed to
edit. Check "admin/input formats" and make sure the role has permission
to submit with that input format.

ex. A node is submitted with "Full HTML" input format and the role
is granted edit permissions but the role only has permission to submit
with "filtered HTML" input format. The role will not be allowed to edit.

Ref: http://www.dartmouth.edu/~rc/help/faq/permissions.html

Understanding file permissions on Unix: a brief tutorial

(For files on AFS fileservers, see below)

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Every user on a Unix system has a unique username, and is a member of
at least one group (the primary group for that user). This group
information is held in the password file (/etc/passwd). A user can
also be a member of one or more other groups. The auxiliary group

This module creates node based permissions view/edit by role(group).
Tested and deployed.

A neccessary addition if you want to mix public and private content.