Access Control Lists, or ACLs, provide an extension to the standand Linux file permissions. In order to use ACLs on a filesystem, the filesystem must be mounted with the acl option:

mount -o acl /home

You can set this option in /etc/fstab:

/dev/volume/home  /home   ext3  acl 1 2

or use tune2fs to set it as a default mount option:

tune2fs -o acl /dev/volume/home

To set ACLs for a file or directory, use the setfacl -m command.

To set an ACL for a user, use the following:

setfacl -m u:[user name]:[permissions] /directory/file

Example:
setfacl -m u:ray:rx /home/foo.txt

This gives the user ray read and execute access to the /home/foo.txt file.

To set an ACL for a group, use the following:

setfacl -m g:[group name]:[permissions] /directory/file

Example:
setfacl -m g:accounting:rwx /finance/foo.txt

This gives the group accounting read, write, and execute access to /finance/foo.txt.

To remove an ACL, use the following:

setfacl -x u:[user name] /directory/file

Example:
setfacl -x u:ray /home/foo.txt

This removes the user ray's read and execute permissions from the /home/foo.txt file.

To check the ACLs associated with a particular file, use the following:

getfacl /directory/file

Example:
getfacl /home/foo.txt

This will get the ACL information about /home/foo.txt. The output will look something like this:

# getfacl /home/foo.txt

getfacl: Removing leading '/' from absolute path names
# file: home/foo.txt
# owner: root
# group: root
user::rw-
user:ray:rx
group::r--
group:marketing:rwx
mask::rwx
other::r--

More information about Access Control Lists can be found on the setfacl and getfacl man pages.