The Volume GUID directory entry contains a GUID which enables implementations to uniquely and programmatically distinguish volumes. The Volume GUID exists as a benign primary directory entry in the root directory (see Table 32). The valid number of Volume GUID directory entries ranges from 0 to 1.

Table 32 Volume GUID DirectoryEntry

Field NameOffset(byte)Size(byte)Comments
EntryType01This field is mandatory and Section 7.5.1 defines its contents.
SecondaryCount11This field is mandatory and Section 7.5.2 defines its contents.
SetChecksum22This field is mandatory and Section 7.5.3 defines its contents.
GeneralPrimaryFlags42This field is mandatory and Section 7.5.4 defines its contents.
VolumeGuid616This field is mandatory and Section 7.5.5 defines its contents.
Reserved2210This field is mandatory and its contents are reserved.

7.5.1 EntryType Field

The EntryType field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1).

7.5.1.1 TypeCode Field

The TypeCode field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.1).

For the Volume GUID directory entry, the valid value for this field is 0.

7.5.1.2 TypeImportance Field

The TypeImportance field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.2).

For the Volume GUID directory entry, the valid value for this field is 1.

7.5.1.3 TypeCategory Field

The TypeCategory field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.3).

7.5.1.4 InUse Field

The InUse field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.4).

7.5.2 SecondaryCount Field

The SecondaryCount field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.2).

For the Volume GUID directory entry, the valid value for this field is 0.

7.5.3 SetChecksum Field

The SetChecksum field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.3).

7.5.4 GeneralPrimaryFlags Field

The GeneralPrimaryFlags field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.4) and defines the contents of the CustomDefined field to be reserved.

7.5.4.1 AllocationPossible Field

The AllocationPossible field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.4.1).

For the Volume GUID directory entry, the valid value for this field is 0.

7.5.4.2 NoFatChain Field

The NoFatChain field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.4.2).

7.5.5 VolumeGuid Field

The VolumeGuid field shall contain a GUID which uniquely identifies the given volume.

All possible values for this field are valid, except the null GUID, which is {00000000-0000-0000-0000-000000000000}.