Access Control Lists; Mounting File Systems; Setting Access Acls - Red Hat ENTERPRISE LINUX 3 System Administration Manual

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 can not be configured for different users. Thus, Access Control Lists (ACLs)
were implemented.
The Red Hat Enterprise Linux 3 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
utilities used to add, modify, remove, and retrieve ACL information.
The and commands copy or move any ACLs associated with files and directories.
cp mv

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
For example:
mount -t ext3 -o acl /dev/hdb3 /work
Alternatively, if the partition is listed in the
the option:
acl
LABEL=/work
If an ext3 file system is accessed via Samba and ACLs have been enabled for it, the ACLs are rec-
ognized because Samba has been compiled with the
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
file. To disable ACLs on an NFS share when mounting it on a client, mount it with
/etc/exports
the option via the command line or the
no_acl

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.
acl
device-name
<
/work ext3
package is required to implement ACLs. It contains the
partition
> < >
file, the entry for the partition can include
/etc/fstab
acl 1 2
--with-acl-support
/etc/fstab
Chapter 8.
option. No special flags
no_acl
file.
option in the