Old Depreciated Tape Format
The format of the Block Header (version 1.26 and earlier) is:
uint32_t CheckSum; /* Block check sum */
uint32_t BlockSize; /* Block byte size including the header */
uint32_t BlockNumber; /* Block number */
char ID[4] = "BB01"; /* Identification and block level */
The format of the Record Header (version 1.26 or earlier) is:
uint32_t VolSessionId; /* Unique ID for this session */
uint32_t VolSessionTime; /* Start time/date of session */
int32_t FileIndex; /* File index supplied by File daemon */
int32_t Stream; /* Stream number supplied by File daemon */
uint32_t DataSize; /* size of following data record in bytes */
Current Bacula Tape Format
6 June 2001
Version BB01 is the old deprecated format.
A Bacula tape is composed of tape Blocks. Each block
has a Block header followed by the block data. Block
Data consists of Records. Records consist of Record
Headers followed by Record Data.
:=======================================================:
| |
| Block Header |
| (16 bytes version BB01) |
|-------------------------------------------------------|
| |
| Record Header |
| (20 bytes version BB01) |
|-------------------------------------------------------|
| |
| Record Data |
| |
|-------------------------------------------------------|
| |
| Record Header |
| (20 bytes version BB01) |
|-------------------------------------------------------|
| |
| ... |
Block Header: the first item in each block. The format is
shown below.
Partial Data block: occurs if the data from a previous
block spills over to this block (the normal case except
for the first block on a tape). However, this partial
data block is always preceded by a record header.
Record Header: identifies the Volume Session, the Stream
and the following Record Data size. See below for format.
Record data: arbitrary binary data.
Block Header Format BB01 (deprecated)
:=======================================================:
| CheckSum (uint32_t) |
|-------------------------------------------------------|
| BlockSize (uint32_t) |
|-------------------------------------------------------|
| BlockNumber (uint32_t) |
|-------------------------------------------------------|
| "BB01" (char [4]) |
:=======================================================:
BBO1: Serves to identify the block as a
Bacula block and also servers as a block format identifier
should we ever need to change the format.
BlockSize: is the size in bytes of the block. When reading
back a block, if the BlockSize does not agree with the
actual size read, Bacula discards the block.
CheckSum: a checksum for the Block.
BlockNumber: is the sequential block number on the tape.
VolSessionId: a unique sequential number that is assigned
by the Storage Daemon to a particular Job.
This number is sequential since the start
of execution of the daemon.
VolSessionTime: the time/date that the current execution
of the Storage Daemon started. It assures
that the combination of VolSessionId and
VolSessionTime is unique for all jobs
written to the tape, even if there was a
machine crash between two writes.
Record Header Format BB01 (deprecated)
:=======================================================:
| VolSessionId (uint32_t) |
|-------------------------------------------------------|
| VolSessionTime (uint32_t) |
|-------------------------------------------------------|
| FileIndex (int32_t) |
|-------------------------------------------------------|
| Stream (int32_t) |
|-------------------------------------------------------|
| DataSize (uint32_t) |
:=======================================================:
VolSessionId: a unique sequential number that is assigned
by the Storage Daemon to a particular Job.
This number is sequential since the start
of execution of the daemon.
VolSessionTime: the time/date that the current execution
of the Storage Daemon started. It assures
that the combination of VolSessionId and
VolSessionTime is unique for all jobs
written to the tape, even if there was a
machine crash between two writes.
FileIndex: a sequential file number within a job. The
Storage daemon enforces this index to be
greater than zero and sequential. Note,
however, that the File daemon may send
multiple Streams for the same FileIndex.
The Storage Daemon uses negative FileIndices
to identify Session Start and End labels
as well as the End of Volume labels.
Stream: defined by the File daemon and is intended to be
used to identify separate parts of the data
saved for each file (attributes, file data,
...). The Storage Daemon has no idea of
what a Stream is or what it contains.
DataSize: the size in bytes of the binary data record
that follows the Session Record header.
The Storage Daemon has no idea of the
actual contents of the binary data record.
For standard Unix files, the data record
typically contains the file attributes or
the file data. For a sparse file
the first 64 bits of the data contains
the storage address for the data block.
Volume Label
:=======================================================:
| Id (32 bytes) |
|-------------------------------------------------------|
| VerNum (uint32_t) |
|-------------------------------------------------------|
| label_date (float64_t) |
|-------------------------------------------------------|
| label_time (float64_t) |
|-------------------------------------------------------|
| write_date (float64_t) |
|-------------------------------------------------------|
| write_time (float64_t) |
|-------------------------------------------------------|
| VolName (128 bytes) |
|-------------------------------------------------------|
| PrevVolName (128 bytes) |
|-------------------------------------------------------|
| PoolName (128 bytes) |
|-------------------------------------------------------|
| PoolType (128 bytes) |
|-------------------------------------------------------|
| MediaType (128 bytes) |
|-------------------------------------------------------|
| HostName (128 bytes) |
|-------------------------------------------------------|
| LabelProg (32 bytes) |
|-------------------------------------------------------|
| ProgVersion (32 bytes) |
|-------------------------------------------------------|
| ProgDate (32 bytes) |
|-------------------------------------------------------|
:=======================================================:
Id: 32 byte Bacula identifier "Bacula 1.0 immortal\n"
(old version also recognized:)
Id: 32 byte Bacula identifier "Bacula 0.9 mortal\n"
LabelType (Saved in the FileIndex of the Header record).
PRE_LABEL -1 Volume label on unwritten tape
VOL_LABEL -2 Volume label after tape written
EOM_LABEL -3 Label at EOM (not currently implemented)
SOS_LABEL -4 Start of Session label (format given below)
EOS_LABEL -5 End of Session label (format given below)
label_date: Julian day tape labeled
label_time: Julian time tape labeled
write_date: Julian date tape first used (data written)
write_time: Julian time tape first used (data written)
VolName: "Physical" Volume name
PrevVolName: The VolName of the previous tape (if this tape is
a continuation of the previous one).
PoolName: Pool Name
PoolType: Pool Type
MediaType: Media Type
HostName: Name of host that is first writing the tape
LabelProg: Name of the program that labeled the tape
ProgVersion: Version of the label program
ProgDate: Date Label program built
Session Label
:=======================================================:
| Id (32 bytes) |
|-------------------------------------------------------|
| VerNum (uint32_t) |
|-------------------------------------------------------|
| JobId (uint32_t) |
|-------------------------------------------------------|
| *write_date (float64_t) VerNum 10 |
|-------------------------------------------------------|
| *write_time (float64_t) VerNum 10 |
|-------------------------------------------------------|
| PoolName (128 bytes) |
|-------------------------------------------------------|
| PoolType (128 bytes) |
|-------------------------------------------------------|
| JobName (128 bytes) |
|-------------------------------------------------------|
| ClientName (128 bytes) |
|-------------------------------------------------------|
| Job (128 bytes) |
|-------------------------------------------------------|
| FileSetName (128 bytes) |
|-------------------------------------------------------|
| JobType (uint32_t) |
|-------------------------------------------------------|
| JobLevel (uint32_t) |
|-------------------------------------------------------|
| FileSetMD5 (50 bytes) VerNum 11 |
|-------------------------------------------------------|
Additional fields in End Of Session Label
|-------------------------------------------------------|
| JobFiles (uint32_t) |
|-------------------------------------------------------|
| JobBytes (uint32_t) |
|-------------------------------------------------------|
| start_block (uint32_t) |
|-------------------------------------------------------|
| end_block (uint32_t) |
|-------------------------------------------------------|
| start_file (uint32_t) |
|-------------------------------------------------------|
| end_file (uint32_t) |
|-------------------------------------------------------|
| JobErrors (uint32_t) |
|-------------------------------------------------------|
| JobStatus (uint32_t) VerNum 11 |
:=======================================================:
* => fields deprecated
Id: 32 byte Bacula Identifier "Bacula 1.0 immortal\n"
LabelType (in FileIndex field of Header):
EOM_LABEL -3 Label at EOM
SOS_LABEL -4 Start of Session label
EOS_LABEL -5 End of Session label
VerNum: 11
JobId: JobId
write_btime: Bacula time/date this tape record written
write_date: Julian date tape this record written - deprecated
write_time: Julian time tape this record written - deprecated.
PoolName: Pool Name
PoolType: Pool Type
MediaType: Media Type
ClientName: Name of File daemon or Client writing this session
Not used for EOM_LABEL.
See also
Possible Next Steps
Go back to Storage Media Output Format.
Go back to Developer Guide.