The back up and restore process specified in the Lustre manual; sections 14.8.4, 14.8.5, and 17.3; need to be reviewed and, if necessary, modified to specify the "lustre" and "trusted" xattrs be restored explicitly rather than assuming tar will do this automatically. The correct usage of tar for back up is

tar --xattrs -cf <backup>.tar <file list>

To extract files,

tar --xattrs-include=lustre.* -xf <backup>.tar