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Old 07-23-2010, 10:27 PM
"Joseph L. Casale"
 
Default ssh and dd

Tonight I have to boot a diskless server with iLO and dd a remote image available by ssh
onto a usb key. As there is no local place to store the image, whats the most efficient
cmd to push the image from the remote server using ssh into the local pipe pushing out
to `dd of=/dev/sdx`?

Would a remote execution of `dd if=/dev/sdx` be the best over ssh? I suppose I could use
nc and do away with ssh, is that in the CentOS rescue mode?

Thanks,
jlc
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Old 07-23-2010, 11:29 PM
Ross Walker
 
Default ssh and dd

On Jul 23, 2010, at 6:27 PM, "Joseph L. Casale" <jcasale@activenetwerx.com> wrote:

> Tonight I have to boot a diskless server with iLO and dd a remote image available by ssh
> onto a usb key. As there is no local place to store the image, whats the most efficient
> cmd to push the image from the remote server using ssh into the local pipe pushing out
> to `dd of=/dev/sdx`?
>
> Would a remote execution of `dd if=/dev/sdx` be the best over ssh? I suppose I could use
> nc and do away with ssh, is that in the CentOS rescue mode?

How about remote cpio?

-Ross

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Old 07-24-2010, 01:32 AM
Jim Wildman
 
Default ssh and dd

YOu can ssh to it and mount an iso from a web server as well.

On Fri, 23 Jul 2010, Ross Walker wrote:

> On Jul 23, 2010, at 6:27 PM, "Joseph L. Casale" <jcasale@activenetwerx.com> wrote:
>
>> Tonight I have to boot a diskless server with iLO and dd a remote image available by ssh
>> onto a usb key. As there is no local place to store the image, whats the most efficient
>> cmd to push the image from the remote server using ssh into the local pipe pushing out
>> to `dd of=/dev/sdx`?
>>
>> Would a remote execution of `dd if=/dev/sdx` be the best over ssh? I suppose I could use
>> nc and do away with ssh, is that in the CentOS rescue mode?
>
> How about remote cpio?
>
> -Ross
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>

----------------------------------------------------------------------
Jim Wildman, CISSP, RHCE jim@rossberry.com http://www.rossberry.com
"Society in every state is a blessing, but Government, even in its best
state, is a necessary evil; in its worst state, an intolerable one."
Thomas Paine
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Old 07-24-2010, 01:34 AM
Les Mikesell
 
Default ssh and dd

Joseph L. Casale wrote:
> Tonight I have to boot a diskless server with iLO and dd a remote image available by ssh
> onto a usb key. As there is no local place to store the image, whats the most efficient
> cmd to push the image from the remote server using ssh into the local pipe pushing out
> to `dd of=/dev/sdx`?
>
> Would a remote execution of `dd if=/dev/sdx` be the best over ssh? I suppose I could use
> nc and do away with ssh, is that in the CentOS rescue mode?
>

dd over ssh should be a sure thing. If you do a lot of image copies remote or
otherwise you might want to try clonezilla-live. It knows enough about most
file systems to only copy the used blocks and can access the image store with
smb, nfs, or ssh.

--
Les Mikesell
lesmikesell@gmail.com
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Old 07-24-2010, 02:38 AM
"Joseph L. Casale"
 
Default ssh and dd

>dd over ssh should be a sure thing. If you do a lot of image copies remote or
>otherwise you might want to try clonezilla-live. It knows enough about most
>file systems to only copy the used blocks and can access the image store with
>smb, nfs, or ssh.

Yeah not lots, just an esxi update...
I'll look into cpio now, its backing up as we speak.

Thanks guys!
jlc
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Old 07-25-2010, 04:50 PM
Gordon Messmer
 
Default ssh and dd

On 07/23/2010 04:29 PM, Ross Walker wrote:
>
> How about remote cpio?

cpio requires rsh/ssh to reach a remote system, and would be a poor
choice for copying an image to a block device.
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Old 07-25-2010, 10:26 PM
Ross Walker
 
Default ssh and dd

On Jul 25, 2010, at 12:50 PM, Gordon Messmer <yinyang@eburg.com> wrote:

> On 07/23/2010 04:29 PM, Ross Walker wrote:
>>
>> How about remote cpio?
>
> cpio requires rsh/ssh to reach a remote system, and would be a poor
> choice for copying an image to a block device.

Better then dd over ssh, but clonezilla would be a better choice overall I think if it can read/write from a pipe, even better if it can resume from a broken pipe.

-Ross

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Old 07-26-2010, 07:54 PM
Gordon Messmer
 
Default ssh and dd

On 07/25/2010 03:26 PM, Ross Walker wrote:
>
> Better then dd over ssh,

Well, no... If you're trying to do an *image*, you'll find that cpio
can't write an image out to a block device.

It's fairly easy to make dd as bandwidth efficient as clonezilla.

1: Clear all of the unused blocks on the local filesystem which you want
to image:
# dd if=/dev/zero of=/mnt/zero
# rm /mnt/zero

2: Copy your filesystem to a file:
# umount /mnt
# dd if=/dev/sdb1 of=/var/tmp/fs.img

3: Compress your filesystem image:
# bzip2 /var/tmp/fs.img

4: Copy the image to the remote system:
# ssh root@remote 'bzip2 -dc | dd of=/dev/sda1' < /var/tmp/fs.img.bz2

Can't get much better than that for low-volume copies. If you need to
repeat the process on a lot of machines, clonezilla gives you some nice
options. If you're copying files instead of images, cpio might be useful.
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Old 07-27-2010, 09:15 AM
John Doe
 
Default ssh and dd

From: Gordon Messmer <yinyang@eburg.com>

> Well, no... If you're trying to do an *image*, you'll find that cpio
> can't write an image out to a block device.
> It's fairly easy to make dd as bandwidth efficient as clonezilla.

Maybe have a look at ddrescue, which handles errors a little bit better than
plain dd...

JD



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