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Old 03-28-2006, 05:03 AM   #106
AwesomeMachine
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Post Make and Recombine Split Files with dd


Quote:
Originally Posted by nerdful1
Is there anyone out there?
repeat:So can you answer my question I asked at 5:34pm 2 days ago? how to use DD to recombine files split using dd and pipe to split. Not using cat. I am not looking for shortcuts. I want to learn all the proper dd stuff. thanks
clip from the past:So can you answer my question I asked at 5:34pm today? how to use DD to recombine files split using dd and pipe to split. Not using cat. I am not looking for shortcuts. I want to learn all the proper dd stuff. thanks
For real dd warriors, you can make split files and recombine them using dd.

You have a 30 GB partition and want to make (3) 10 GB files.

dd if=/dev/sourcepartition ibs=4k count=2.5M | gzip | of=/home/sam/file1.gz

dd if=/dev/sourcepartition ibs=4k count=2.5M skip=2.5M | gzip | of=/home/sam/file2.gz

dd if=/dev/sourcepartition ibs=4k count=2.5M skip=5M | gzip | of=/home/sam/file3.gz

Put them back into a partition:

dd if=/home/sam/file1.gz ibs=4k | gunzip | of=/dev/sourcepartition

dd if=/home/sam/file2.gz ibs=4k | gunzip | of=/dev/sourcepartition seek=2.5M

dd if=/home/sam/file3.gz ibs=4k | gunzip | of=/dev/sourcepartition seek=5M


This would not be a productive use of time. I wouldn't answer right away because this post is unimportant. Tar can do the same thing by itself, so why use dd? Jinkels is right. You can't use dd for everything.

Last edited by AwesomeMachine; 04-13-2006 at 04:16 PM.
 
Old 03-28-2006, 12:46 PM   #107
nerdful1
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thank you very much. It may not be efficient, but now I think I have a concept of the process.
If I have any more dd problems piping, I'll drop the pipe stuff and go manual as seems to be recommended to me. Sorry If I bothered anyone, but I am learning a lot.
 
Old 04-12-2006, 01:10 PM   #108
bugmenot60
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Quote:
Originally Posted by AwesomeMachine
dd if=/dev/sdb2 ibs=4096 | tar zc | of=/home/sam/partition.image.tar.gz conv=noerror
I tried the above command on my Linux box with Fedora Core 5,
and it didn't work.

The error I got was "tar: Cowardly refusing to create an empty archive."

Could somebody clue me in on what I am doing wrong?

I tried changing the "tar zc" to "tar -zc" and it still didn't work.

Thank you.
 
Old 04-12-2006, 06:17 PM   #109
jlinkels
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I think there is an error in the way tar is called.

tar MUST have a file spec of the files to archive. Stdin or stdout are only used for the archive file. You cannot use stdin as input for tar as a stream to archive. This means that you can write:
Code:
tar -zcf myarchive.tar *.c
to tar all your .c files into myarchive.tar, or alternatively:
Code:
tar -zc *.c
to get the tar file dumped on stdout.

However,
Code:
cat *.c | tar -zcf myarchive.tar
is not supposed to work as far as I know.

Which means that the example given by Awesome doesn't work. Awesome, could I be correct?

Besides, it is a waste of time to try and use dd in this way.

jlinkels
 
Old 04-12-2006, 08:22 PM   #110
bugmenot60
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Quote:
Originally Posted by jlinkels
Besides, it is a waste of time to try and use dd in this way.

jlinkels
What do you suggest then?

Fedora Core 5 doesn't have partimage installed by default.
 
Old 04-12-2006, 09:33 PM   #111
jlinkels
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It depends what you want to achieve, because that is not completely clear to me.

If you want to make an image of your disk or of each partition, use dd. And forget about the tar.

If you want to make a backup of your disk, use tar.

If you insist of multi-volume, download and use star. This is a sort of extended tar, and very versatile and powerful. It can do multivolumes.

In the latter two cases, forget about dd.

Is FC so rigid that you cannot install parted if you really need that?

To Awesome: if you have the idea that your thread is hijacked, I cannot deny that it looks like that. Sorry, it is not my intention. If you think it is annoying, please ask a mod to split the thread.

jlinkels

Last edited by jlinkels; 04-12-2006 at 09:36 PM.
 
Old 04-13-2006, 01:45 PM   #112
bugmenot60
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I have a 10 gig partition with Windows in it, and I want to make an image of
that Windows partition without the image itself taking 10 gigs. I usually use
partimage on a Knoppix live CD to image the partition and compressed, it is
only a couple gigs.

If I use dd, then the image file will be 10 gigs and I am trying to avoid that.

I think Awesome's post uses "tar" just for compressing. Thanks for any help/
insight you can provide.

P.S. The reason why I need the image of the Windows partition is b/c I have
to keep restoring the damn thing due to Wind0ze's inherent instabilities and
problems.
 
Old 04-13-2006, 03:01 PM   #113
jlinkels
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I have not tested it extensively, but I would say:

dd if=/dev/sdb2 ibs=4096 | bzip2 -v > image.bz2

and the other way around:

bzip2 -v -c image.bz2 | dd of=/dev/sdb2

Be careful with the latter command, it wipes out your sdb2 partition. And I am not 100% certain that this is the right command as I did NOT test it for obvious reasons.

Further nice features of bzip2 in the man page.

jlinkels
 
Old 04-13-2006, 04:17 PM   #114
AwesomeMachine
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See my revised post

Quote:
Originally Posted by jlinkels
I think there is an error in the way tar is called.

tar MUST have a file spec of the files to archive. Stdin or stdout are only used for the archive file. You cannot use stdin as input for tar as a stream to archive. This means that you can write:
Code:
tar -zcf myarchive.tar *.c
to tar all your .c files into myarchive.tar, or alternatively:
Code:
tar -zc *.c
to get the tar file dumped on stdout.

However,
Code:
cat *.c | tar -zcf myarchive.tar
is not supposed to work as far as I know.

Which means that the example given by Awesome doesn't work. Awesome, could I be correct?

Besides, it is a waste of time to try and use dd in this way.

jlinkels
The tar command does not work between pipes, but gzip does. See revised post.
 
Old 04-13-2006, 09:10 PM   #115
jlinkels
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Awesome,

That is gonna work either. At the moment the output from dd hits the pipe, it is going into gzip. Gzip expects a gzip output file (or maybe another pipe), but it will not understand
... gzip | of=somefile.

I think you could pipe gzip output into another instance of dd like:
... gzip | dd of=somefile
(but what would be the use of that?)

or alternatively you could redirect gzip's output directpy to a file:
... gzip > somefile

jlinkels
 
Old 04-18-2006, 11:10 PM   #116
AwesomeMachine
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I tried it. It works. I assumed tar would do the same thing, but tar won't work between pipes.
 
Old 04-19-2006, 03:37 AM   #117
kncharyulu
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Very Good Article!!!!!!!!!
 
Old 04-25-2006, 03:46 AM   #118
gubak
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Linux clone problem

I cloned my linux HDD with dd command yesterday, but I have some problems.
My linux HDD has the following partitions:
Device Boot Start End Blocks ID System
/dev/hda1 * 1 13 10439 83 Linux
/dev/hda2 14 9954 79851082+ 83 Linux
/dev/hda3 9955 10011 457852+ 82 Linux swap

First I shuted down my linux os and connected a HDD with the same parameters as my linux HDD. After that I switched on the system. The new HDD became /dev/hdc. After that I type the command:
dd if=/dev/hda of=/dev/hdc
and a couple of hours later I get the message that copying is successfully completed (or something similar). After that my second HDD (/dev/hdc) had completely the same partitions as my primary HDD:

Device Boot Start End Blocks ID System
/dev/hdc1 * 1 13 10439 83 Linux
/dev/hdc2 14 9954 79851082+ 83 Linux
/dev/hdc3 9955 10011 457852+ 82 Linux swap

So I thinked that if I disconnected my primary (Linux) HDD, and I started machine with secondary HDD it would work, but unfortunately not. If I start machine with clone HDD, I get the command "Kernel panic".
Why?

Last edited by gubak; 10-04-2006 at 01:09 AM.
 
Old 04-27-2006, 03:03 AM   #119
AwesomeMachine
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There are so many possible reasons for this.

Quote:
Originally Posted by gubak
I cloned my linux HDD with dd command yesterday, but I have some problems.
My linux HDD has the following partitions:
Device Boot Start End Blocks ID System
/dev/hda1 * 1 13 10439 83 Linux
/dev/hda2 14 9954 79851082+ 83 Linux
/dev/hda3 9955 10011 457852+ 82 Linux swap

First I shuted down my linux os and connected a HDD with the same parameters as my linux HDD. After that I switched on the system. The new HDD became /dev/hdc. After that I type the command:
dd if=/dev/hda of=/dev/hdc
and a couple of hours later I get the message that copying is successfully completed (or something similar). After that my second HDD (/dev/hdc) had completely the same partitions as my primary HDD:

Device Boot Start End Blocks ID System
/dev/hdc1 * 1 13 10439 83 Linux
/dev/hdc2 14 9954 79851082+ 83 Linux
/dev/hdc3 9955 10011 457852+ 82 Linux swap

So I thinked that if I disconnected my primary (Linux) HDD, and I started machine with secondary HDD it would work, but unfortunately not. If I start machine with clone HDD, I get the command "Kernel panic".
Why?
I really can't say, from the tiny amount of information you have given, why this wouldn't work. I could give a whole bunch of different reasons, which would all fit the data given, but this would lead to confusion for other people reading the thread. What would be much better is for you to ask the question in a way that a definitive answer could be given. I do what you described all the time. I never have had a problem. The first thing I would look at is the partition table in the MBR. If the disks are different sizes, the geometry of the second disk is probably off. This would make the boot loader jump to the wrong place on the drive to find the kernel.
 
Old 04-30-2006, 12:14 PM   #120
harys
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dd and dvd film

hi, could you please tell me if it is possible to use dd with gnomebaker to burn a dvd film. if possible how do i process ? thanks. harys
 
  


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