La acrobacia

The right on a file make it possible to restrict the accesses to a file, according to certain a number of parameters. It is one of the bases of the Computer security.

Presentation

The three principal rights on file S are:

the reading
the writing
the execution

The execution of a file corresponds:

for a program: with its execution, its launching
for a repertory: to enter inside

Under UNIX

See the detailed article: Permissions Unix

Under UNIX and its derivatives (Linux, FreeBSD, etc) the various rights are associated with three types of users:

the owner of the file
users belonging to the group to which the file
belongs all the other user

Many combinations are possible. One can thus allow to the other users the reading and the execution of a file (or of a repertory), but not his modification (in other words its writing), etc

This system has a limit, it does not allow a final tuning. It is for example impossible to give the same rights as oneself to a user in particular. To mitigate these gaps was conceived the systems of ACL.

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