[patch] read-devices

[Donovan Baarda]

On Mon, Aug 05, 2002 at 10:28:38AM +0300, Eran Tromer wrote:
> Greetings,
> 
> I'd like to propose a new option to rsync, which causes it to read 
> device files as if they were regular files. This includes pipes, 
> character devices and block devices (I'm not sure about sockets). The 
> main motivation is cases where you need to synchronize a large amount of 
> data that is not available as regular files, as in the following scenarios:
> 
> * Keep a copy of a block device
> http://rsync.samba.org/cgi-bin/rsync.fom?auth=ckdf646d354e73&editCmds=compact&file=87
> 
> * Make backups using a huge tar file instead of actual files, to prevent 
> need to be root in order to preserve attributes:
> http://rsync.samba.org/cgi-bin/rsync.fom?auth=ckdf646d354e73&editCmds=compact&file=228
> 
> * Keep an SQL-formatted dump of database tables (i.e., output of 
> mysqldump) for backup purposes
> 
> In all three cases, using a temporary file may require unreasonable 
> amounts of additional diskspace, and there is no good reason to mandate it.

I'm not that familiar with rsync code at the lowest level, but I'm guessing
this patch adds support for in-place patching, possibly without reverse
seeks in the basis.

How does this work? Does it have an adverse affect on the delta size? Have I
got this wrong and it just allows the source to be a device, still requiring
a temporary file for target creation?

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