The /etc/mtab.shadowfs file is an XML file that contains an entry for each shadow volume mounted by ShadowFS. It lists the mount point, the path for the primary file tree, and the path for the secondary file tree.
For example, the following XML entry defines the DST shadow volume for ShadowFS named VOL1:
<SHADOWFS_MOUNTPOINTS>
<MOUNTPOINT>
<PATH>/media/shadowfs/VOL1</PATH>
<PRIMARY_TREE>/media/nss/VOL1</PRIMARY_TREE>
<SHADOW_TREE>/media/nss/ARCVOL</SHADOW_TREE>
</MOUNTPOINT>
</SHADOWFS_MOUNTPOINTS>