If an ACL has been set on any file on a given file system, that file system has the
ext_attr attribute. This attribute can be seen using the following command:
tune2fs -l <filesystem-device>
A file system that has acquired the
ext_attr attribute can be mounted with older kernels, but those kernels do not enforce any ACLs which have been set.
Versions of the
e2fsck utility included in version 1.22 and higher of the
e2fsprogs package (including the versions in Red Hat Enterprise Linux 2.1 and 4) can check a file system with the
ext_attr attribute. Older versions refuse to check it.