Setting Access Acls - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Chapter 8.
Access Control Lists
Files and directories have permission sets for the owner of the file, the group associated with the file,
and all other users for the system. However, these permission sets have limitations. For example,
different permissions cannot be configured for different users. Thus, Access Control Lists (ACLs) were
implemented.
The Red Hat Enterprise Linux 5 kernel provides ACL support for the ext3 file system and NFS-
exported file systems. ACLs are also recognized on ext3 file systems accessed via Samba.
Along with support in the kernel, the acl package is required to implement ACLs. It contains the
utilities used to add, modify, remove, and retrieve ACL information.
The cp and mv commands copy or move any ACLs associated with files and directories.
8.1. Mounting File Systems
Before using ACLs for a file or directory, the partition for the file or directory must be mounted with
ACL support. If it is a local ext3 file system, it can mounted with the following command:
mount -t ext3 -o acl <device-name> <partition>
For example:
mount -t ext3 -o acl /dev/VolGroup00/LogVol02 /work
Alternatively, if the partition is listed in the /etc/fstab file, the entry for the partition can include the
acl option:
LABEL=/work /work ext3 acl 1 2
If an ext3 file system is accessed via Samba and ACLs have been enabled for it, the ACLs are
recognized because Samba has been compiled with the --with-acl-support option. No special
flags are required when accessing or mounting a Samba share.
8.1.1. NFS
By default, if the file system being exported by an NFS server supports ACLs and the NFS client can
read ACLs, ACLs are utilized by the client system.
To disable ACLs on NFS shares when configuring the server, include the no_acl option in the /
etc/exports file. To disable ACLs on an NFS share when mounting it on a client, mount it with the
no_acl option via the command line or the /etc/fstab file.

8.2. Setting Access ACLs

There are two types of ACLs: access ACLs and default ACLs. An access ACL is the access control list
for a specific file or directory. A default ACL can only be associated with a directory; if a file within the
directory does not have an access ACL, it uses the rules of the default ACL for the directory. Default
ACLs are optional.
ACLs can be configured:
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