f



Are "disk images" disk images or not?

I have seen the question "What are disk images" answered numerous times
with the assurance that they are exact sector-by-sector copies of real
physical disks. But my own eyes seem to contradict that apparently
standard answer.

Disregarding the instant .dmg "images" which can be cobbled together in
folders on the desktop, and concentrating on sincere attempts to create
real images of real physical disks with Disk Utility, if .dmg's are real
sector-by-sector copies, how come they shrink in size when files are
deleted from their source-devices to make the "images" fit on dvd ?

Can Disk Utility make, or is it even claiming to make, real images of
real physical disks?

Does anyone actually know?
0
tinkerer (32)
6/1/2009 1:26:36 PM
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Tinkerer Atlarge wrote:
> I have seen the question "What are disk images" answered numerous times
> with the assurance that they are exact sector-by-sector copies of real
> physical disks. But my own eyes seem to contradict that apparently
> standard answer.

There are many forms of disk images. Some are the standard sector by sector
copy of the entire disk. Some are a virtual disk, which can grow or shrink 
as files are moved.

Then just to really complicate things, a disk image can be compressed and or
encrypted. 

All can be read and created with the various incarnations of the OSX Disk 
Utility, which at one time was two different programs and most have the file
type .dmg. 

The CD(DVD) ROM images used for burning disks have the file type .cdr.

There are various utilities for reading .dmg files on other platforms, some
are more successful than others. 

Geoff.


-- 
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
0
gsm (601)
6/1/2009 1:39:04 PM
On 2009-06-01, Tinkerer Atlarge <tinkerer@optusnet.com.au> wrote:

> Can Disk Utility make, or is it even claiming to make, real images of
> real physical disks?

From your description of what you think a "real" image is, if you want 
to make one then just use dd(1).

Disk Utility can be used to package a directory into a .dmg file that 
can then be mounted as if it were a disk. As I understand it there is no 
claim that it makes anything like what you are calling a "real" image.

I look forward to reading other responses - I might be surprised.

Ian

-- 
Ian Gregory
http://www.zenatode.org.uk/ian/
0
foo37 (895)
6/1/2009 1:42:11 PM
In article <1j0nm6m.1ulwrn017m4utoN%tinkerer@optusnet.com.au>,
 tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:

> I have seen the question "What are disk images" answered numerous times
> with the assurance that they are exact sector-by-sector copies of real
> physical disks. But my own eyes seem to contradict that apparently
> standard answer.
> 
> Disregarding the instant .dmg "images" which can be cobbled together in
> folders on the desktop, and concentrating on sincere attempts to create
> real images of real physical disks with Disk Utility, if .dmg's are real
> sector-by-sector copies, how come they shrink in size when files are
> deleted from their source-devices to make the "images" fit on dvd ?
> 
> Can Disk Utility make, or is it even claiming to make, real images of
> real physical disks?
> 
> Does anyone actually know?

It doesn't make sector-perfect copies and doesn't claim to. There's also 
virtually no need to for a mainstream user.

-- 
I saw a truck today that had "AAA Batteries / Delivered and Installed" on the
side. My first thought was: That's a really weird business model. How many
inept people have urgent need of skinny little battery cells?
0
uce3 (3721)
6/1/2009 5:53:28 PM
Gregory Weston wrote:

> It doesn't make sector-perfect copies and doesn't claim to. There's also 
> virtually no need to for a mainstream user.

Physical copy of a disk can be of tremendous use when you have a failing
disk and you are willing to accept loss of already damaged sectors in
order to salvage the rest before the disk completely dies.

You can then use tools on your copy to try to fix broken structures to
recover files.

One way to test if the .dmg creators are able to make physical copies is
to load a CD whose structure is unknown to OS-X. (for instance , a VMS
CD). I should try this later on to see if it can be done.

If OS-X is able to make an image it would mean that it would be a
physical image since OS-X would not understand the file structure.
0
6/1/2009 10:22:47 PM
JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> Physical copy of a disk can be of tremendous use when you have a failing
> disk and you are willing to accept loss of already damaged sectors in
> order to salvage the rest before the disk completely dies.
> 
> You can then use tools on your copy to try to fix broken structures to
> recover files.

Why do you think copying to a disk image would have an advantage to just
copying to another drive?

-- 
Tribute to Humphrey Bogart <http://bogart-tribute.net>

Mac and geek T-shirts & gifts <http://designsbymike.net/shop/mac.cgi>
Prius shirts/bumper stickers <http://designsbymike.net/shop/prius.cgi>
0
mikePOST (4990)
6/1/2009 10:29:11 PM
Gregory Weston <uce@splook.com> wrote:

> In article <1j0nm6m.1ulwrn017m4utoN%tinkerer@optusnet.com.au>,
>  tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:
> 
> > I have seen the question "What are disk images" answered numerous times
> > with the assurance that they are exact sector-by-sector copies of real
> > physical disks. But my own eyes seem to contradict that apparently
> > standard answer.
[ ... ]
> > Can Disk Utility make, or is it even claiming to make, real images of
> > real physical disks?
> > 
> > Does anyone actually know?
>
> It doesn't make sector-perfect copies and doesn't claim to. 

Thanks to everyone for the replies. I am now satisfied Disk Utility
isn't claiming to make sector-by-sector copies of disks according to
current use of the terminology.

Maybe it's a case of the meaning of "disk copy" evolving into something
different without a corresponding adjustment to the terminology. As GSM
pointed out, Disk Utility is a merger of two formerly different
utilities. One of those, I believe, was "Disk Copy". I understood
"diskcopy" and "filecopy" were two distinct concepts. Perhaps the
earlier need to distinguish is no longer relevant.

Or maybe frequent reference to .dmgs as "images" refers to the way it is
deposited on a CDROM track? I'm not sure if that is the case either.

Failing either of those explanations, the almost universal use of the
word "image" in describing .dmg files would appear to be a mystery.
0
tinkerer (32)
6/2/2009 12:00:34 AM
JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> One way to test if the .dmg creators are able to make physical copies is
> to load a CD whose structure is unknown to OS-X. (for instance , a VMS
> CD). I should try this later on to see if it can be done.
> 
> If OS-X is able to make an image it would mean that it would be a
> physical image since OS-X would not understand the file structure.

Trying the opposite with highly suspect results is what led to my
initial question.

I used Disk Utility to make a compressed .dmg of an OSX-unmountable ext3
partition containing over a gigabyte of data. The resulting .dmg was
only 8 MB, casting serious doubt on my former assumption that .dmg's
were images of disk partitions regardless of their contents.
0
tinkerer (32)
6/2/2009 12:00:34 AM
Geoffrey S. Mendelson <gsm@mendelson.com> wrote:

> The CD(DVD) ROM images used for burning disks have the file type .cdr.

Is this what the "image" in .img and .dmg refers to? The DVD or CDROM
track it sometimes ends up as?
0
tinkerer (32)
6/2/2009 12:04:42 AM
In article <1j0oguk.xw6sk71uxsvkeN%tinkerer@optusnet.com.au>,
 tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:

> > The CD(DVD) ROM images used for burning disks have the file type 
> > .cdr.
> 
> Is this what the "image" in .img and .dmg refers to? The DVD or CDROM 
> track it sometimes ends up as?

It has nothing to do with a DVD or CD ROM.

-- 
Member National Rifle Association
Member American Civil Liberties Union
Member Human Rights Campaign
0
michelle14 (19004)
6/2/2009 12:28:39 AM
In article <1j0oe4p.1x76yx31fke3wuN%tinkerer@optusnet.com.au>,
 tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:

> Thanks to everyone for the replies. I am now satisfied Disk Utility
> isn't claiming to make sector-by-sector copies of disks according to
> current use of the terminology.
> 
> Maybe it's a case of the meaning of "disk copy" evolving into something
> different without a corresponding adjustment to the terminology. As GSM
> pointed out, Disk Utility is a merger of two formerly different
> utilities. One of those, I believe, was "Disk Copy". I understood
> "diskcopy" and "filecopy" were two distinct concepts. Perhaps the
> earlier need to distinguish is no longer relevant.
> 
> Or maybe frequent reference to .dmgs as "images" refers to the way it is
> deposited on a CDROM track? I'm not sure if that is the case either.
> 
> Failing either of those explanations, the almost universal use of the
> word "image" in describing .dmg files would appear to be a mystery.

When a .dmg file in mounted, it is essentially indistinguishable from a 
"real" disk and the term "image" seems quite appropriate.

-- 
Tom Stiller

PGP fingerprint =  5108 DDB2 9761 EDE5 E7E3  7BDA 71ED 6496 99C0 C7CF
0
tom_stiller (1288)
6/2/2009 12:37:16 AM
Tom Stiller <tom_stiller@yahoo.com> wrote:

> In article <1j0oe4p.1x76yx31fke3wuN%tinkerer@optusnet.com.au>,
>  tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:
> 
> > Thanks to everyone for the replies. I am now satisfied Disk Utility
> > isn't claiming to make sector-by-sector copies of disks according to
> > current use of the terminology.
....
> > Failing either of those explanations, the almost universal use of the
> > word "image" in describing .dmg files would appear to be a mystery.
> 
> When a .dmg file in mounted, it is essentially indistinguishable from a
> "real" disk and the term "image" seems quite appropriate.

To me as well. I don't see "image" as necessarily implying an exact copy
of the underlying structure. After all, a photographic image is not an
exact copy of the photographic subject; it just has a simillar
appearance when you look at it with your eyes. Likewise, a disk image
has the same appearance as a disk when you look at it through the file
system. If you look beyond the surface, it will certainly differ at some
level (for sure at the physical level, and likely at quite a bit higher
level as well), just like an image of a beautiful woman differs a lot
from a real woman beneath the surface (and for that matter, the
resemblance even fails rather poorly as soon as you get to the surface).

-- 
Richard Maine                    | Good judgment comes from experience;
email: last name at domain . net | experience comes from bad judgment.
domain: summertriangle           |  -- Mark Twain
0
nospam47 (9747)
6/2/2009 12:49:29 AM
Just tried.

Inserted a VMS CD (hi-sierra format). OS-X tells me it doesn't know
this, so I "ignore" instead of "eject".

Disk Utility calls the disk disk0s1 or something like that.

It allows me to click on "restore", but does not let me drag it to the
"source" field.

Also, when you create a .dmg file with disk utility, it forces you to
specify a valid format mountable by OS-X.

This would mean that the disk utility would not have the ability to do
raw disk copy (physical sectors) as it insists on understanding the file
structure of both source and destination.


I assume that there is some unix utility that can do raw
sector-by-sector copy.
0
6/2/2009 1:02:06 AM
JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> Just tried.
> 
> Inserted a VMS CD (hi-sierra format). OS-X tells me it doesn't know
> this, so I "ignore" instead of "eject".
> 
> Disk Utility calls the disk disk0s1 or something like that.
> 
> It allows me to click on "restore", but does not let me drag it to the
> "source" field.
> 
> Also, when you create a .dmg file with disk utility, it forces you to
> specify a valid format mountable by OS-X.
> 
> This would mean that the disk utility would not have the ability to do
> raw disk copy (physical sectors) as it insists on understanding the file
> structure of both source and destination.
> 
> 
> I assume that there is some unix utility that can do raw
> sector-by-sector copy.

What does any of this have to do with the question I asked in the post
you responded to?

-- 
Tribute to Humphrey Bogart <http://bogart-tribute.net>

Mac and geek T-shirts & gifts <http://designsbymike.net/shop/mac.cgi>
Prius shirts/bumper stickers <http://designsbymike.net/shop/prius.cgi>
0
mikePOST (4990)
6/2/2009 1:18:39 AM
On Mon, 1 Jun 2009 20:49:29 -0400, Richard Maine wrote:
> If you look beyond the surface, it will certainly differ at some
> level (for sure at the physical level, and likely at quite a bit higher
> level as well),

You're right: It has to differ, and that's what's confusing. Think about the 
meaning of "exact image" as it relates to, say, a common CD or even a simple 
Mac volume. You can't take the first bit (and I mean bit as in byte) of data 
and start merrily writing away on your hard drive, copying the exact data 
bit-for-bit -- you must at least have a wrapper around it or at least 
introduce what it is to the operating system or it will be total garbage.

0
no-spam2 (6830)
6/2/2009 2:07:19 AM
Tim Murray wrote:

> You're right: It has to differ, and that's what's confusing. Think about the 
> meaning of "exact image" as it relates to, say, a common CD or even a simple 
> Mac volume. You can't take the first bit (and I mean bit as in byte) of data 
> and start merrily writing away on your hard drive, copying the exact data 
> bit-for-bit -- you must at least have a wrapper around it or at least 
> introduce what it is to the operating system or it will be total garbage.

Actually, the container file itself can be an exact bit by bit copy of
the original drive. You can set file attributes (such as the file
extemsion) to invoke some handler that will mount this file as a disk
and use appropriate drivers.

I have used this on VMS. Did a physical backup of a corrupt drive to a
container file, and then used the disk image driver (LDdrive) to create
a disk device which I could then play with without touching the originla
drive. WIth a physical copy, you have access to blocks that are marked
"free" due to files being deleted by mistake for instance, and you can
use tools to recover it.

With a "logical" disk image (as disk utility does), it will not copy
blocks it considers unused into the container file and will recreate a
totally new drive which will *look* the same to you even thought it
won't be the same deep down.


With a physical copy, then a file in the reative boocks 1000 to 2000 on
the disk will be in relative blocks 1000 to 2000 on the container file.

With a logical image copy, files will not be in the same location in the
container fiel as they were in the original disk.
0
6/2/2009 9:30:23 AM
In article <001d4dfb$0$29042$c3e8da3@news.astraweb.com>,
 JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> Gregory Weston wrote:
> 
> > It doesn't make sector-perfect copies and doesn't claim to. There's also 
> > virtually no need to for a mainstream user.
> 
> Physical copy of a disk can be of tremendous use when you have a failing
> disk and you are willing to accept loss of already damaged sectors in
> order to salvage the rest before the disk completely dies.
> 
> You can then use tools on your copy to try to fix broken structures to
> recover files.
> 
> One way to test if the .dmg creators are able to make physical copies is
> to load a CD whose structure is unknown to OS-X. (for instance , a VMS
> CD). I should try this later on to see if it can be done.
> 
> If OS-X is able to make an image it would mean that it would be a
> physical image since OS-X would not understand the file structure.

OK, I just whipped a VMS documentation CD off the shelf...

On inserting it, I get a message that it's an unrecognizable format and 
a prompt to Ignore or Eject - this depends on the user settings in 
System Preferences.  IIRC the defaults supplied by OS X will simply 
eject the disk straight away.

Next I fired up Disk Utility and could see the disk as "Untitled 0". 
Right clicking on the disk and selecting "Information" gives me:

    Disk Identifier :    disk2s0

and then I can enter the following command to copy it.

sudo dd if=/dev/disk2s0 of=~/vmsdisk.iso

I think that's the correct incantation, it gives the correct sized 
output (as reported by Disk Utility) file of 629.9 MB

Another way to look at the CD is:

diskutil list

/dev/disk2
   #:                   type name           size      identifier
   0:    CD_partition_scheme                *723.4 MB disk2
   1:          CD_ROM_Mode_1                629.9 MB  disk2s0
 

Hmm... Out of curiosity I repeated the above dd command, but using 
/dev/disk2 and it gave me an output file of 723.4 MB.  I'm not sure
which one I should use for transferring to another system for reading. I 
may risk creating a coaster or two later on to see what happens.

-- 
Paul Sture
0
6/2/2009 10:03:09 AM
On 2009-06-02, JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> I assume that there is some unix utility that can do raw 
> sector-by-sector copy.

Of course there is:-) If you want to copy /dev/rdisk1 to /dev/rdisk2 
(assuming they are identical drives with a sector size of N bytes) you 
would just do:

dd -bs=N if=/dev/rdisk1 of=/dev/rdisk2

Or you could just copy /dev/rdisk1 to a file on /dev/rdisk0 (assuming it 
has enough space to hold it):

dd -bs=N if=/dev/rdisk1 of=IMAGEFILE

IMAGEFILE would then be an exact image of /dev/rdisk1 which you could 
examine with any tools want, or copy later onto another identical disk:

dd -bs=N if=IMAGEFILE of=/dev/rdisk2

Ian

-- 
Ian Gregory
http://www.zenatode.org.uk/ian/
0
foo37 (895)
6/2/2009 12:39:57 PM
In article <paul.sture.nospam-0A94F9.12030902062009@mac.sture.ch>, "P. Sture" <paul.sture.nospam@hispeed.ch> writes:
>In article <001d4dfb$0$29042$c3e8da3@news.astraweb.com>,
> JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:
>
>> Gregory Weston wrote:
>> 
>> > It doesn't make sector-perfect copies and doesn't claim to. There's also 
>> > virtually no need to for a mainstream user.
>> 
>> Physical copy of a disk can be of tremendous use when you have a failing
>> disk and you are willing to accept loss of already damaged sectors in
>> order to salvage the rest before the disk completely dies.
>> 
>> You can then use tools on your copy to try to fix broken structures to
>> recover files.
>> 
>> One way to test if the .dmg creators are able to make physical copies is
>> to load a CD whose structure is unknown to OS-X. (for instance , a VMS
>> CD). I should try this later on to see if it can be done.
>> 
>> If OS-X is able to make an image it would mean that it would be a
>> physical image since OS-X would not understand the file structure.
>
>OK, I just whipped a VMS documentation CD off the shelf...
>
>On inserting it, I get a message that it's an unrecognizable format and 
>a prompt to Ignore or Eject - this depends on the user settings in 
>System Preferences.  IIRC the defaults supplied by OS X will simply 
>eject the disk straight away.
>
>Next I fired up Disk Utility and could see the disk as "Untitled 0". 
>Right clicking on the disk and selecting "Information" gives me:
>
>    Disk Identifier :    disk2s0
>
>and then I can enter the following command to copy it.
>
>sudo dd if=/dev/disk2s0 of=~/vmsdisk.iso
>
>I think that's the correct incantation, it gives the correct sized 
>output (as reported by Disk Utility) file of 629.9 MB
>
>Another way to look at the CD is:
>
>diskutil list
>
>/dev/disk2
>   #:                   type name           size      identifier
>   0:    CD_partition_scheme                *723.4 MB disk2
>   1:          CD_ROM_Mode_1                629.9 MB  disk2s0
> 
>
>Hmm... Out of curiosity I repeated the above dd command, but using 
>/dev/disk2 and it gave me an output file of 723.4 MB.  I'm not sure
>which one I should use for transferring to another system for reading. I 
>may risk creating a coaster or two later on to see what happens.

Paul,

Why not transfer your vmsimage.iso (BTW, that's a UniCode CD format
on the VMS CDs and not ISO 9660) and then, use LD (the virtual disk
driver) to connect to that file.  Then, $ MOUNT/OVERRIDE=IDENT LDAn:
If your 'dd' copy is made from the appropriate device view of your
CD, it *should* mount on VMS; thus, proving out whether or not your
image will generate coasters or not when you burn them to media.

$ LD CONNECT vmsimage.iso LDA10:
$ MOUNT/OVERRIDE=IDENT LDA10:

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

  http://www.quirkfactory.com/popart/asskey/eqn2.png
  
  "Well my son, life is like a beanstalk, isn't it?"
0
VAXman
6/2/2009 1:52:56 PM
Gregory Weston wrote:

> It doesn't make sector-perfect copies and doesn't claim to. There's also
> virtually no need to for a mainstream user.

Well... now I'm a bit curious...

First of all, Disk Utility has some hidden settings. You can probably
trigger them in the terminal, but an easy way is to get Onyx, go to
"Parameters > Other" and enable "show more disk formats" for Disk Utility.
(the exact titles may be different in English, I'm guessing right now, based
on my localized version).

Once you enabled this, Disk Utility will hugely enhance the "format" popup
in the save-dialog, including an option "copy whole drive".

I was always assuming that this exactly would/should result in a complete
block-by-block copy of the entire drive content.

0
noreply6 (69)
6/2/2009 2:06:10 PM
Addendum...

If you don't want to download/use Onyx for that single task, you can also
simply double-click com.apple.DiskUtility.plist in your Library >
Preferences.

The first entry is "root > advanced-image-options" and you can just set it
from "no" to "yes".

0
noreply6 (69)
6/2/2009 2:52:05 PM
On Tue, 2 Jun 2009 05:30:23 -0400, JF Mezei wrote:
> Actually, the container file itself can be an exact bit by bit copy of
> the original drive. 

Not the "container" -- the contents in it, yes, but not the container itself. 
I guarantee that you didn't just start at the first block of corrupt drive 
and start writing it to another disk at some particular block. Well, you DID, 
but you're writing it sort of "inside" the container that defines it as a 
certain kind of object.

0
no-spam2 (6830)
6/2/2009 3:03:16 PM
JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:

> Actually, the container file itself can be an exact bit by bit copy of
> the original drive.

Well, if I feel like being pedantic, I'll repeat my prior point that it
certainly can't be an exact copy all the way down to every level. In
particular, by saying bit-by-bit, you have already ruled out multiple
lower levels. The original drive doesn't directly have "bits" at the
physical level. In some sense, when talking about bits, you are already
talking about an image or view of what is on the drive. It takes some
processing to turn the physical representation into bits. (I'll
carefully avoid being more specific or I'll probably reveal that I'm
decades out of date on the low-level details; I used to know that stuff,
but I bet some of it has changed).

There are (or sure used to be) drive recovery methodologies that work at
those lower levels. They can sometimes reconstruct the bits.

-- 
Richard Maine                    | Good judgment comes from experience;
email: last name at domain . net | experience comes from bad judgment.
domain: summertriangle           |  -- Mark Twain
0
nospam47 (9747)
6/2/2009 4:11:50 PM
> Once you enabled this, Disk Utility will hugely enhance the "format" popup
> in the save-dialog, including an option "copy whole drive".
> 
> I was always assuming that this exactly would/should result in a complete
> block-by-block copy of the entire drive content.
>

It might be a file-by-file copy instead.  They might not end up in the same
sectors as the original although all files are present on the copy.

Tom Lake

 
0
tlake (477)
6/2/2009 4:39:16 PM
In article <00A8C6F0.5E3F4C1F@SendSpamHere.ORG>,
 VAXman-  @SendSpamHere.ORG wrote:

> In article <paul.sture.nospam-0A94F9.12030902062009@mac.sture.ch>, "P. Sture" 
> <paul.sture.nospam@hispeed.ch> writes:
> >
> >OK, I just whipped a VMS documentation CD off the shelf...
> >
> >On inserting it, I get a message that it's an unrecognizable format and 
> >a prompt to Ignore or Eject - this depends on the user settings in 
> >System Preferences.  IIRC the defaults supplied by OS X will simply 
> >eject the disk straight away.
> >
> >Next I fired up Disk Utility and could see the disk as "Untitled 0". 
> >Right clicking on the disk and selecting "Information" gives me:
> >
> >    Disk Identifier :    disk2s0
> >
> >and then I can enter the following command to copy it.
> >
> >sudo dd if=/dev/disk2s0 of=~/vmsdisk.iso
> >
> >I think that's the correct incantation, it gives the correct sized 
> >output (as reported by Disk Utility) file of 629.9 MB
> >
> >Another way to look at the CD is:
> >
> >diskutil list
> >
> >/dev/disk2
> >   #:                   type name           size      identifier
> >   0:    CD_partition_scheme                *723.4 MB disk2
> >   1:          CD_ROM_Mode_1                629.9 MB  disk2s0
> > 
> >
> >Hmm... Out of curiosity I repeated the above dd command, but using 
> >/dev/disk2 and it gave me an output file of 723.4 MB.  I'm not sure
> >which one I should use for transferring to another system for reading. I 
> >may risk creating a coaster or two later on to see what happens.
> 
> Paul,
> 
> Why not transfer your vmsimage.iso (BTW, that's a UniCode CD format
> on the VMS CDs and not ISO 9660) and then, use LD (the virtual disk
> driver) to connect to that file.  Then, $ MOUNT/OVERRIDE=IDENT LDAn:
> If your 'dd' copy is made from the appropriate device view of your
> CD, it *should* mount on VMS; thus, proving out whether or not your
> image will generate coasters or not when you burn them to media.
> 
> $ LD CONNECT vmsimage.iso LDA10:
> $ MOUNT/OVERRIDE=IDENT LDA10:

What I was trying to ascertain here was how to use dd on the OS X side 
in the first place to grab copies of CDs in a "foreign" format (here 
defined as one that OS X doesn't understand).  It's something I never 
got to grips with when I first got my iBook and ended up finding another 
way.  Better late than never.

What I have verified is that the _filesystem_ I was after was the 629.9 
MB one addressable by dd as /dev/disk2s0 (i.e. the foreign file system 
that's sitting on the CD), and not the vanilla /dev/disk2 as reported by 
"diskutil list".  I am not entirely surprised, but now I know for 
certain.

I didn't realise that the VMS CDs are Unicode - that nugget of 
information answers another question that's been nagging me for several 
years.

For completeness, trying to use LDDRIVER on the full 723.4 MB copy gave 
"%LD-F-UNSUPPORTEDFS, Unsupported filesystem").

Thanks for the input. I'm in the process of packing for a move and my 
Alpha cables are already boxed up. Simh and LDDRIVER got me there.

-- 
Paul Sture
0
6/2/2009 6:21:25 PM
In article <C64B0935.93069%noreply@hotmail.com>,
 MartinC <noreply@hotmail.com> wrote:

> Addendum...
> 
> If you don't want to download/use Onyx for that single task, you can also
> simply double-click com.apple.DiskUtility.plist in your Library >
> Preferences.
> 
> The first entry is "root > advanced-image-options" and you can just set it
> from "no" to "yes".

I don't see that entry there (on Tiger).

However if you have TinkerTool, go to the Applications tab, and check 
"Enable extended options when converting disk images".

It then appears in 

/users/username/Library/Preferences/com.apple.DiskUtility.plist

as enabled.

-- 
Paul Sture
0
6/2/2009 6:41:28 PM
Ok, I used Thinker Tool to enable the "Enable extended options when
converting disk images".

Then, from Disk utility, you click on the grey CD (disk1s0 ), and then
"New Image". You can then specify "entire disk".

It created a 633 megabyte file with .dmg extension.
0
6/3/2009 12:29:40 AM
On 2009-06-02, Ian Gregory <foo@prdetfanaaeextna.invalid> wrote:
> On 2009-06-02, JF Mezei <jfmezei.spamnot@vaxination.ca> wrote:
>
>> I assume that there is some unix utility that can do raw 
>> sector-by-sector copy.
>
> Of course there is:-) If you want to copy /dev/rdisk1 to /dev/rdisk2 
> (assuming they are identical drives with a sector size of N bytes) you 
> would just do:
>
> dd -bs=N if=/dev/rdisk1 of=/dev/rdisk2

I just noticed the spurious "-" characters in my post. That command 
should have read:

dd bs=N if=/dev/rdisk1 of=/dev/rdisk2

Ian

-- 
Ian Gregory
http://www.zenatode.org.uk/ian/
0
foo37 (895)
6/3/2009 11:38:42 AM
Tom Lake wrote:

> It might be a file-by-file copy instead.  They might not end up in the same
> sectors as the original although all files are present on the copy.

OK, it might be - but then I'm curious about the difference between "copy
whole drive" and virtually every other option. You can select "read only"
and "sparse bundle" and "compressed image" and "whatever" and it actually
should *always* copy all files.

So either the option "copy whole drive" is a misleading double-entry for
some of the other options, or it does copy the "unused" blocks as well.

I don't have the time right here and now at the moment to verify it myself,
but it would actually make sense. After all, the whole Disk Utility is
mostly a GUI for the OS-X built-in repair and disk tools, and since you
*can* do a block-by-block copy in the terminal, the GUI may just do it as
well, when enabled.

0
noreply6 (69)
6/3/2009 12:55:53 PM
MartinC <noreply@hotmail.com> wrote:

> OK, it might be - but then I'm curious about the difference between "copy
> whole drive" and virtually every other option. You can select "read only"
> and "sparse bundle" and "compressed image" and "whatever" and it actually
> should *always* copy all files.
> 
> So either the option "copy whole drive" is a misleading double-entry for
> some of the other options, or it does copy the "unused" blocks as well.

I just did two restores of a dmg image I created by dragging my normal
Startup Disk's icon into a Burn Folder prior to re-partitioning the
internal hard drive under OS X 10.4 about a week ago.

The first Disk Utility Restore took almost an hour (3.5 GB compressed
dmg to 8 GB restored). The restored Startup Volume booted and worked ok,
but showed a few worrying imperfections which caused me to eventually
wipe it and start again. Even though I restored the same dmg to a
freshly erased partition both times, on the second attempt I ticked the
seemingly unnecessary "Erase Destination" checkbox. That made an
enormous difference to the style of restore Disk Utility performed.

The second restore gave the status line: "Copying BLOCKS" and took only
about five minutes to restore the whole thing. There was also no trace
of the imperfections and vulnerabilities I had noticed following the
earlier restore. 

My only remaining puzzlement comes about because the Startup partition I
dragged into the Burn Folder was smaller than the resized partition I
restored it back onto. The regular smooth pulses on the drive's activity
light confirmed it was not a file-based restore like the first one. So
whether I now have a smaller partition stamped on top of a nominally
larger one, or whether Disk Utility had the smarts to adjust for the
partition-size mismatch - or if it is even relevant - remains to be
seen.
0
tinkerer (32)
6/8/2009 11:28:33 AM
In article <1j10edu.1opu72cuc3c4cN%tinkerer@optusnet.com.au>,
 tinkerer@optusnet.com.au (Tinkerer Atlarge) wrote:

> MartinC <noreply@hotmail.com> wrote:
> 
> > OK, it might be - but then I'm curious about the difference between "copy
> > whole drive" and virtually every other option. You can select "read only"
> > and "sparse bundle" and "compressed image" and "whatever" and it actually
> > should *always* copy all files.
> > 
> > So either the option "copy whole drive" is a misleading double-entry for
> > some of the other options, or it does copy the "unused" blocks as well.
> 
> I just did two restores of a dmg image I created by dragging my normal
> Startup Disk's icon into a Burn Folder prior to re-partitioning the
> internal hard drive under OS X 10.4 about a week ago.

That's an interesting way to create a disc image. I would have thought 
Burn Folder would only be useful to burn something to optical disc. What 
extra steps are necessary to make it create a DMG file instead?

> The first Disk Utility Restore took almost an hour (3.5 GB compressed
> dmg to 8 GB restored). The restored Startup Volume booted and worked ok,
> but showed a few worrying imperfections which caused me to eventually
> wipe it and start again. Even though I restored the same dmg to a
> freshly erased partition both times, on the second attempt I ticked the
> seemingly unnecessary "Erase Destination" checkbox. That made an
> enormous difference to the style of restore Disk Utility performed.
> 
> The second restore gave the status line: "Copying BLOCKS" and took only
> about five minutes to restore the whole thing. There was also no trace
> of the imperfections and vulnerabilities I had noticed following the
> earlier restore. 

So the DMG created by Burn Folders is always a block copy, then?

Some details about those "imperfections and vulnerabilities" would be 
much appreciated.

-- 
Send responses to the relevant news group rather than email to me.
E-mail sent to this address may be devoured by my very hungry SPAM
filter. Due to Google's refusal to prevent spammers from posting
messages through their servers, I often ignore posts from Google
Groups. Use a real news client if you want me to see your posts.

JR
0
jollyroger (11010)
6/8/2009 12:50:40 PM
In article <jollyroger-B7ECD5.07503908062009@news.individual.net>,
 Jolly Roger <jollyroger@pobox.com> wrote:

> So the DMG created by Burn Folders is always a block copy, then?

I always "scan image for restore" (as it says in DU) once I've created a 
disk image. This sets it up for block copy, I think.
-- 
Suddenly he realized that he was alone 
with a giant halfwit on a dark deserted street.
  -- Chester Himes

0
warren.oates (3828)
6/8/2009 1:54:45 PM
On Mon, 8 Jun 2009 08:50:40 -0400, Jolly Roger wrote:
> What extra steps are necessary to make it create a DMG file instead?

Apple downloads has a few creators of DMG for download.

0
no-spam2 (6830)
6/8/2009 9:10:13 PM
On Jun 8, 10:50=A0pm, Jolly Roger <jollyro...@pobox.com> wrote:
> In article <1j10edu.1opu72cuc3c4cN%tinke...@optusnet.com.au>,
> =A0tinke...@optusnet.com.au (Tinkerer Atlarge) wrote:
>
> > I just did two restores of a dmg image I created by dragging my normal
> > Startup Disk's icon into a Burn Folder prior to re-partitioning the
> > internal hard drive under OS X 10.4 about a week ago.
>
> That's an interesting way to create a disc image. I would have thought
> Burn Folder would only be useful to burn something to optical disc. What
> extra steps are necessary to make it create a DMG file instead?

That's the part that happened a week ago. It is probably inaccurate. I
tried to
repeat that step just now and couldn't. What I probably ended up doing
was
making the image with Disk Utility then copying the image into the
Burn
Folder so that I ended up with just a single dmg file on the DVD. As
far as
I can now recall, I didn't do anything special when creating the dmg
apart
from selecting "compressed" in order to fit it on a 4.7 GB DVD.

> > The first Disk Utility Restore took almost an hour (3.5 GB compressed
> > dmg to 8 GB restored). The restored Startup Volume booted and worked ok=
,
> > but showed a few worrying imperfections which caused me to eventually
> > wipe it and start again. Even though I restored the same dmg to a
> > freshly erased partition both times, on the second attempt I ticked the
> > seemingly unnecessary "Erase Destination" checkbox. That made an
> > enormous difference to the style of restore Disk Utility performed.
>
> > The second restore gave the status line: "Copying BLOCKS" and took only
> > about five minutes to restore the whole thing. There was also no trace
> > of the imperfections and vulnerabilities I had noticed following the
> > earlier restore.
>
> So the DMG created by Burn Folders is always a block copy, then?

Probably not. See above.

> Some details about those "imperfections and vulnerabilities" would be
> much appreciated.

There were extra folder aliases for tmp, etc and var (IIRC) in the
restored
disk's window following my first attempt at restoring. They persisted
after I successfully booted from it. After a while I decided to get
rid
of them by dragging them into the Trash. After that, the restored
system
hung during reboot. I dragged them back out of the trash and put them
back where they came from, but it continued to hang during reboot even
after that. Open Firmware saw them as "slnk rhap", whatever that
means.

The other differences I noticed were really the differences in Disk
Utility's
behaviour during the two Restores previously described. In addition to
the diffs previously mentioned, the Destination partition remained
mounted
during the earlier (slow, flickery) Restore, whereas it remained
absent from
the desktop during and even after the second (smooth, fast) restore. I
got
it back by clicking Unmount, then Mount in Disk Utility following the
restore.
It also lost its name during the restore and ended up with the saved
disk's
original name rather than retaining its new name like the slower
restore.
There are a few other probably related minor differences which I am
now
too hazy about to describe accurately.

As for other "vulnerabilities", I figured that if one hit me in the
eye the moment
I opened the disk icon, there were probably less obvious ones lurking
beneath
the surface somewhere as well..

Cheers

Tink

0
tinkerer (32)
6/9/2009 5:10:56 AM
In article <0001HW.C652F6750011978BF0182648@nntp.charter.net>,
 Tim Murray <no-spam@thankyou.com> wrote:

> On Mon, 8 Jun 2009 08:50:40 -0400, Jolly Roger wrote:
> > What extra steps are necessary to make it create a DMG file instead?
> 
> Apple downloads has a few creators of DMG for download.

He stated he used a Burn Folder to create a DMG file. That's what I'd 
like to know more about.

-- 
Send responses to the relevant news group. E-mail sent to this address
may be devoured by my ravenous SPAM filter. Due to Google's refusal to
prevent spammers from posting messages, I often ignore posts from
Google. Use a real news client if you want me to see your posts.

JR
0
jollyroger (11010)
6/9/2009 5:35:51 AM
Reply:

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Hello, &nbsp; &nbsp; I have built a picture using a 2D Array and then converted it by using the "Array to Image" (Vision Module) and then displayed it using the "Image Display" Control and tried also the "IMAQ WindDraw" vi. The problem is that when I loose focus with the mouse, or open another window, the picture disappears or parts of it are overwritten and are not updated back when I come back to the Image. &nbsp; Is there a way to set the image so that it won't be affected by other actions, and will remain stable ? &nbsp; Thanx The information in <a href="http://forums.ni.com/ni/board/message?board.id=170&amp;message.id=119402#M119402" target="_blank">this</a> post and <a href="http://forums.ni.com/ni/board/message?board.id=170&amp;message.id=114513#M114513" target="_blank">this other </a>post may be of use to you in understanding this. Basically an IMAQ image display is globally accessible in nature and it is easy to update or overwrite it from left-field operations if you are not careful. ...

"Thickness of a region" in an image / Image analysis
Hello - I have images like this one; http://twitpic.com/bbnnnm/full And I really want to do some analysis on them; What I need in the centroid = or the shape, the average distance from the centroid to the border, and the= average thickness of the intensely green region.=20 My method for finding the average thickness is something like this; I greys= cale the image, dilute it several times, then erode it, then hole fill, seg= ment and apply border with sobel filter. Then I use regionsprops to find th= e centroid, and can then calculate the distance from centroid to border. This works, but can run into problems when the Green region is fragmented, = which happens quite a bit. Is there a more elegant way? Finally, any suggestions on how to work out the thickness of the green regi= on?=20 Thanks in advance! ...

Size of "image"-images' pixels
Hello, which size will a pixel have, that is used with the image-operator? Didn't found a specification for it. TIA, Oliver P.S.: Why are those pixels not sharp displayed? When I use the examples from the Bluebook, I got smeared grafics, so there are not sharp edges. Looks like aliasing or something like that..?! In article <1115414000.431902@elch.in-berlin.de>, Oliver Bandel <oliver@first.in-berlin.de> wrote: >which size will a pixel have, that is used >with the image-operator? > >Didn't found a specification for it. Look in the PLRM in the Operator Details section. The image is considered to exist in its own coordinate system, or image space. The rectangular boundary of the image has its lower-left corner at coordinates (0, 0) and its upper-right corner at (width, height). The matrix operand defines a transformation from user space to image space. -- -- Rod -- rodd(at)polylogics(dot)com ...

What is "image"
Hi, I often heard that "image" is used in embedded application. This is something to do with a pointer and it is common to use "image" to configure the peripheral Integrated Circuit (IC). What is this "image" actually ? Why and When we use "image" ? Thanks in advance. The term "image" is most often used for identical memory locations, which can be accessed at different addresses. That happens when addresses are incompletely decoded. A very simple example: an 8-bit CPU might have a total address space of 64kB, i.e. it has 16 address lines (A0..A15). You reserve the upper half for some peripheral registers by selecting these registers if A15 is high. If you use the lower four bits (A0..A3) to select one out of 16 registers, then you can address the first of these registers with any address from 0x8??0...0xf??0. The question mark means that any combination is valid. In other words, an access to 0x8000 adresses the same data as 0x8010. 0x8010 is called an image of 0x8000. "Wong" <tatto0_2000@yahoo.com> wrote in message news:509bfe22.0502110306.641c47c6@posting.google.com... > Hi, > I often heard that "image" is used in embedded application. This is > something to do with a pointer and it is common to use "image" to > configure the peripheral Integrated Circuit (IC). > What is this "image" actually ? Why and When we use "image" ? > Thanks in a...

Disk Utility
In Disk Utility one can "Unmount" or "Eject" the volume on a physical device. What's the difference? Does unmount logically disconnect it but not "eject" the physical media (on devices that can eject)? -- "Civilization is the limitless multiplication of unnecessary necessities." -Samuel Clemens. In article <z7idneeI6ug9ombSnZ2dnUVZ_rIAAAAA@giganews.com>, Alan Browne <alan.browne@FreelunchVideotron.ca> wrote: > > In Disk Utility one can "Unmount" or "Eject" the volume on a physical > device. > > What's the difference? Does unmount logically disconnect it but not > "eject" the physical media (on devices that can eject)? Yes, it does what you say last. If you eject, it physically turfs it out of the tray or whatever you have. You can mount something you have unmounted but you can't mount something that is ejected. See the Mount menu come alive when you merely Unmount. A bit like that you can kill a person and then never be able to talk to them or just put them in coventry and still not talk to them. -- dorayme On 2012-07-09 18:56 , dorayme wrote: > In article <z7idneeI6ug9ombSnZ2dnUVZ_rIAAAAA@giganews.com>, > Alan Browne <alan.browne@FreelunchVideotron.ca> wrote: > >> >> In Disk Utility one can "Unmount" or "Eject" the volume on a physical &g...

MAC SE: "Bomb" "Sys Error" / Address error" at start
Stephen Buggie (505) 863-2390 Psychology Department Univ. of New Mexico, Gallup February 15, 2006 200 College Road Gallup NM 87301 buggie@unm.edu NEED RESCUE DISK! MAC SE -- BOMB System Error / Address Error ------------------------------------------------------------------------------------------------ Dear Macintosh experts, My Mac SE crashes at power-up. I gives the bell-chime, then it proceeds though the launch sequence. After showing two extension-icons, it crashes. Then a dialogue-box shows the BOMB icon with the message, SORRY, A SYSTEM ERROR HAS OCCURRED --- ADDRESS ERROR It never reaches the desktop; this crash occurs every time. The Mac SE has a 330 meg internal hard drive, System 6.x.x, and a 1.4 meg internal 3.5 floppy drive. There is a SCSI port but no internal CD reader. The b/w screen is extremely sharp in its focus. The computer worked fine until about a year ago, when I stupidly put a file in the wrong folder. It has crashed consistently ever since! It has an assortment of software on the hard drive, but I have backups of everything and am willing to reformat the entire hard drive if necessary to get the computer working again! If I can resurrect the computer, I hope to upgrade the system to System 7.0 or 7.1 . DONE SO FAR: Yes, I have launched it with shift-key down, to turn off the extensions, but it always crashes Ive also tried vari...

"Invalid System Disk..." Error
OK, I'm attempting to install FreeBSD 5.3 on this AST Ascentia P laptop with a swappable floppy/CD-ROM drive. Windows 95 was originally installed so I formatted the hard drive and set the BIOS to boot from the CD-ROM drive. When I reboot, nothing happens, and I have to open the CD drive and close it again and repeat that process about 3 times before it reads the CD and I receive the "invalid system disk - replace the disk and press any key" message. I've tried using multiple CDs and I still receive the error. Any ideas? Tim Tim O'Neal wrote: > OK, I'm attempting to install FreeBSD 5.3 on this AST Ascentia P laptop > with a swappable floppy/CD-ROM drive. Windows 95 was originally > installed so I formatted the hard drive and set the BIOS to boot from > the CD-ROM drive. When I reboot, nothing happens, and I have to open > the CD drive and close it again and repeat that process about 3 times > before it reads the CD and I receive the "invalid system disk - replace > the disk and press any key" message. I've tried using multiple CDs and > I still receive the error. Any ideas? Is that old enough that it doesn't recognize a CD-R/RW? ISTR that early CD drives would only read CD-ROM. If you were using CD-RW, try CD-R. Do you have an original Win95 CD you could try to boot off of? Is booting from floppies and doing an install over the 'net an option for you? Maybe b...

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