POSIX.1 Permission Bit Mechanism
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The POSIX.1 standard specifies the use of the permission
bit mechanism that is currently implemented and used in many
POSIX-like systems. This mechanism allows the defined permissions of
read, write and execute to be specified for:
- the file owner,
- the group of users specified as the ``owning group,'' and
- all other users (named ``other'').
This mechanism can be cumbersome to use if permissions need
to be specified for a named user who is not the owner (and nearly
impossible to specify separate permissions for two users, neither of whom
is the owner). It is also not possible to provide specific permissions
for different named groups of users. These limitations pointed to
the need to provide a Discretionary Access
Control mechanism that can provide the granularity of specifying individual
users and named groups. The POSIX.6 standard specifies an access
control list mechanism to provide this functionality.
John Barkley
Fri Oct 7 16:17:21 EDT 1994