List of ods5 specific mount options
- option bs=blocksize
ODS-2/5 disks have a default blocksize of 512 bytes. CDs/DVSs when formatted with
ODS-2/-5 have a blocksize of 2048 bytes. Disk images usually have the size of the disk,
but comtainer files can be any size (and multiple of 512 byte blocks).
To optimize the I/Os for the ods5 filesystem the blocksize can be set with the bs option.
Default is bs=512. Other possible values are 1024, 2048 and 4096. For CDs one would use bs=2048, for
disk images or container files - if they are a multiple of 4096, any of these values
can be used. Actually, you can use bs=4096 on most of the disk images and even hard disks
as long as the last blocks of that device aren't used. But in case of using a non-default value
and the ods5 file system reports an "Input/output error", mount the file system without the
bs option and try again.
- option dirless (not yet implemented)
Directories always have the suffix '.DIR;1'. That can be suppressed for
input and output. The
master file directory shows as '000000'. This does not conflict with a file
that has a name '000000'. That file will show as '000000.;1'.
This will make it easier to look
at /mnt/000000/000000/000000/ which is - as we know - still the
masterfile directory.
- option dotversion
Change the ';' to something easier to deal with in shells: '.'. Then the
master file directory will be '000000.DIR.1' and the file
'.;1' will be '..1'. A dot shows in the output of 'ls' and can be used as
input as well. (For input this in not new for VMS users, but that doesn't
matter, here.) However, the dotversion option is silently disabled when the
syml option is also specified.
- option home=lbn
Use an alternate home block with the specified block number, a non-zero
decimal value.
By default ods5 uses lbn 1, the second block on the disk,
also known as the primary home block (lbn zero
usually is the boot block). ODS disks which require a GPT, for Integrity
servers, do not have a primary
home block: the GPT is expected at the first disk blocks. VMS then uses an
alternate home block. Depending on the size of the ODS disk, good candidates
for alternate home blocks are 1034,
2067, ...
The ods5 file
system does not try to find an alternate home block. But it tries to use any
lbn
as specified with the 'home=' option. To find the first two (alternate) home
blocks simply do a
# od -a -Ax small.dsk | grep -m2 'D E C F I L E 1 1 B' 0047f0 D E C F I L E 1 1 B sp sp nul nul e x 0049f0 D E C F I L E 1 1 B sp sp nul nul i x # printf "%d\n" $((0x47f0/512)) 35 # mount -v -o ro,loop -t ods5 -o home=35 small.dsk /mnt- option mode=omask