rsync - Dec 2018 - rsync remote raw block device with --inplace

It would be very nice to be able to rsync the raw data content of, e.g., a
non-mounted disk partition, particularly in combination with --inplace.

Our reality: several dual-boot machines running Windows during the day and
Linux at night, during backups.  Windows is very tedious and iffy to
re-reinstall without a raw disk image to start from.  Disks fail, and the
ensuing downtime must be minimized.

We're using dd for this.  Most of the nightly work is redundant and
wasteful of elapsed time and storage.  Storage is cheap, but it's not
*that* cheap.  Elapsed time is priceless.

Rsync refuses to back up raw devices, and even raw character devices, with
the message "skipping non-regular file" (I think the relevant message
is in
generator.c).

In Linux, anyway, the "raw" command allows a block device to be bound
as a
character device, and then even a "cat" command can read the raw data
of
the block device.  So why does rsync refuse to copy such content, or why is
it a bad idea, or what rsync doctrine conflicts with it?  I agree there are
security concerns here, but rsync already disallows some of its functions
unless the super user is requesting them.
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There have been addons to rsync in the past to do that but rsync really
isn't the correct tool for the job.  Neither is dd.

The right tool is something that understands the filesystem within the
block device such as ntfsclone (what I use) or partimage (if you have
ever used Clonezilla this is what it uses).  These will know how to skip
all the empty parts of the filesystem and will still be capable of
restoring a complete image in a bare metal restore.  You can still use
dd to snag a copy of the MBR since that is outside of any filesystems.

Also, if you do have to resort to a plain image use ddrescue instead of
dd.  It has a status screen and it can resume as long as you used a log
file when you ran it.

On 12/30/18 1:45 PM, Steve Newcomb via rsync wrote:
> It would be very nice to be able to rsync the raw data content of, e.g.,
> a non-mounted disk partition, particularly in combination with --inplace.
> 
> Our reality: several dual-boot machines running Windows during the day
> and Linux at night, during backups.  Windows is very tedious and iffy to
> re-reinstall without a raw disk image to start from.  Disks fail, and
> the ensuing downtime must be minimized. 
> 
> We're using dd for this.  Most of the nightly work is redundant and
> wasteful of elapsed time and storage.  Storage is cheap, but it's not
> *that* cheap.  Elapsed time is priceless.
> 
> Rsync refuses to back up raw devices, and even raw character devices,
> with the message "skipping non-regular file" (I think the
relevant
> message is in generator.c). 
> 
> In Linux, anyway, the "raw" command allows a block device to be
bound as
> a character device, and then even a "cat" command can read the
raw data
> of the block device.  So why does rsync refuse to copy such content, or
> why is it a bad idea, or what rsync doctrine conflicts with it?  I agree
> there are security concerns here, but rsync already disallows some of
> its functions unless the super user is requesting them. 
> 
> 
-- 
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,
	Kevin Korb			Phone:    (407) 252-6853
	Systems Administrator		Internet:
	FutureQuest, Inc.		Kevin at FutureQuest.net  (work)
	Orlando, Florida		kmk at sanitarium.net (personal)
	Web page:			https://sanitarium.net/
	PGP public key available on web site.
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,

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> There have been addons to rsync in the past to do that but rsync really
> isn't the correct tool for the job.
why not correct tool ?

if rsync can greatly keep two large files in sync between source and destination
(using --inplace), why should it (generally spoken) not also be used to keep two
blockdevices in sync ? 

maybe these links are interesting in that context:

https://lists.samba.org/archive/rsync/2010-June/025164.html

https://github.com/dop251/diskrsync

roland
> Gesendet: Sonntag, 30. Dezember 2018 um 19:53 Uhr
> Von: "Kevin Korb via rsync" <rsync at lists.samba.org>
> An: rsync at lists.samba.org
> Betreff: Re: rsync remote raw block device with --inplace
>
> There have been addons to rsync in the past to do that but rsync really
> isn't the correct tool for the job.  Neither is dd.
> 
> The right tool is something that understands the filesystem within the
> block device such as ntfsclone (what I use) or partimage (if you have
> ever used Clonezilla this is what it uses).  These will know how to skip
> all the empty parts of the filesystem and will still be capable of
> restoring a complete image in a bare metal restore.  You can still use
> dd to snag a copy of the MBR since that is outside of any filesystems.
> 
> Also, if you do have to resort to a plain image use ddrescue instead of
> dd.  It has a status screen and it can resume as long as you used a log
> file when you ran it.
> 
> On 12/30/18 1:45 PM, Steve Newcomb via rsync wrote:
> > It would be very nice to be able to rsync the raw data content of,
e.g.,
> > a non-mounted disk partition, particularly in combination with
--inplace.
> > 
> > Our reality: several dual-boot machines running Windows during the day
> > and Linux at night, during backups.  Windows is very tedious and iffy
to
> > re-reinstall without a raw disk image to start from.  Disks fail, and
> > the ensuing downtime must be minimized. 
> > 
> > We're using dd for this.  Most of the nightly work is redundant
and
> > wasteful of elapsed time and storage.  Storage is cheap, but it's
not
> > *that* cheap.  Elapsed time is priceless.
> > 
> > Rsync refuses to back up raw devices, and even raw character devices,
> > with the message "skipping non-regular file" (I think the
relevant
> > message is in generator.c). 
> > 
> > In Linux, anyway, the "raw" command allows a block device to
be bound as
> > a character device, and then even a "cat" command can read
the raw data
> > of the block device.  So why does rsync refuse to copy such content,
or
> > why is it a bad idea, or what rsync doctrine conflicts with it?  I
agree
> > there are security concerns here, but rsync already disallows some of
> > its functions unless the super user is requesting them. 
> > 
> > 
> 
> -- 
>
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,
> 	Kevin Korb			Phone:    (407) 252-6853
> 	Systems Administrator		Internet:
> 	FutureQuest, Inc.		Kevin at FutureQuest.net  (work)
> 	Orlando, Florida		kmk at sanitarium.net (personal)
> 	Web page:			https://sanitarium.net/
> 	PGP public key available on web site.
>
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,
> 
> -- 
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