[Info-vax] questions on initialize/gpt

[hb]

On 06/23/2015 07:26 PM, Simon Clubley wrote:
> I knew the blocks allocated to GPT.SYS were allocated to protect a
> console visible partition on IA-64 but I had thought it was VMS
> $ init itself which created that console visible partition. Oh well. :-)

Have a look, any VMS user can do this (and very likely will get a better
formatted output than shown here):

DEMO$ ld create gpt.dsk /size=10000
DEMO$ ld connect gpt.dsk
%LD-I-UNIT, Allocated device is $9$LDA11:
DEMO$ init $9$LDA11: gpt/gpt
DEMO$ mount $9$LDA11: gpt
%MOUNT-I-MOUNTED, GPT mounted on _$9$LDA11: (JACK)
DEMO$ sh dev/full $9$LDA11:

Disk $9$LDA11: (JACK), device type Generic SCSI disk, is online, allocated,
    deallocate on dismount, mounted, file-oriented device, shareable.

    Error count                    0    Operations completed
   1169
    Owner process             "DEMO"    Owner UIC
[DEMO_GROUP,DEMO]
    Owner process ID        21A04748    Dev Prot
S:RWPL,O:RWPL,G:R,W
    Reference count                2    Default buffer size
    512
    Total blocks               10000    Sectors per track
     10
    Total cylinders              100    Tracks per cylinder
     10
    Logical Volume Size        10000    Expansion Size Limit
  12288
    Allocation class               9

    Volume label               "GPT"    Relative volume number
      0
    Cluster size                   1    Transaction count
      1
    Free blocks                 9899    Maximum files allowed
   2500
    Extend quantity                5    Mount count
      1
    Mount status             Process    Cache name
"_$4$DKA0:XQPCACHE"
    Extent cache size             64    Max blocks in extent cache
    989
    File ID cache size            64    Blocks in extent cache
      0
    Quota cache size               0    Maximum buffers in FCP cache
   4624
    Volume owner UIC  [DEMO_GROUP,DEMO]
                                        Vol Prot
S:RWCD,O:RWCD,G:RWCD,W:RWCD

  Volume Status:  ODS-2, subject to mount verification, file high-water
marking,
      write-through XFC caching enabled, write-back XQP caching enabled.

DEMO$
DEMO$ dump/header/bl=co=0 disk$gpt:[000000]gpt.sys


Dump of file DISK$GPT:[000000]GPT.SYS;1 on 23-JUN-2015 17:54:44.06
File ID (11,11,0)   End of file block 68 / Allocated 68

                             File Header

Header area
    Identification area offset:           40
    Map area offset:                      100
    Access control area offset:           255
    Reserved area offset:                 255
    Extension segment number:             0
    Structure level and version:          2, 1
    File identification:                  (11,11,0)
    Extension file identification:        (0,0,0)
    VAX-11 RMS attributes
        Record type:                      Fixed
        File organization:                Sequential
        Record attributes:                <none specified>
        Record size:                      512
        Highest block:                    68
        End of file block:                69
        End of file byte:                 0
        Bucket size:                      0
        Fixed control area size:          0
        Maximum record size:              512
        Default extension size:           0
        Global buffer count:              0
        Directory version limit:          0
    File characteristics:                 MoveFile disabled
    Caching attribute:                    No_caching
    Map area words in use:                4
    Access mode:                          0
    File owner UIC:                       [DEMO_GROUP,DEMO]
    File protection:                      S:RWED, O:RWED, G:RE, W:E
    Back link file identification:        (4,4,0)
    Journal control flags:                <none specified>
    Active recovery units:                None
    File entry linkcount:                 0
    Highest block written:                68
    Client attributes:                    None

Identification area
    File name:                            GPT.SYS;1
    Revision number:                      1
    Creation date:                        23-JUN-2015 17:54:05.80
    Revision date:                        23-JUN-2015 17:54:05.80
    Expiration date:                      <none specified>
    Backup date:                          <none specified>

Map area
    Retrieval pointers
        Count:         34        LBN:          0
        Count:         34        LBN:       9966

Checksum:                                 55300
DEMO$

Which shows what the GPT.SYS covers: the protective MBR, the primary GPT
and the secondary GPT. The size of the GPT is 33 Blocks. It looks like
INIT wastes one block, the one at LBN 9999. For more info on the GPT:
https://en.wikipedia.org/wiki/GUID_Partition_Table.

And you can copy the LD disk image to your system and get a second
opinion of other OSes on this GPT:

$ losetup -f
/dev/loop0
$ losetup -f ./gpt.dsk
$ parted /dev/loop0
GNU Parted 2.3
Using /dev/loop0
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Warning: /dev/loop0 contains GPT signatures, indicating that it has a
GPT table.
However, it does not have a valid fake msdos partition table, as it should.
Perhaps it was corrupted -- possibly by a program that doesn't
understand GPT
partition tables.  Or perhaps you deleted the GPT table, and are now
using an
msdos partition table.  Is this a GPT partition table?
Yes/No? yes
Error: Both the primary and backup GPT tables are corrupt.  Try making a
fresh
table, and using Parted's rescue feature to recover partitions.
(parted) quit
$