An important thing to realize, if you wish to use xattr, you need a filesystem that has extended attributes functionalty and also has those enabled! I lost quite a bit of time with puzzling why xattr was not working with my ext4 system, until I found that the extended attributes, by default, are not enabled.
Adding user_xattr to the mounting configuration of the filesystem where I was working fixed the problem
/dev/sdb2 /home ext4 relatime,user_xattr 0 2
To use xattr, you will need libattr installed. It is available at » http://oss.sgi.com/projects/xfs/.
These functions only work on filesystems that support extended attributes, and have them enabled at mount time. Some common filesystems that support extended attributes are ext2, ext3, reiserfs, jfs, and xfs.