Re: incremental backup

Sandro Dentella wrote:
> hi all,

Hello,

> 
>    I just started using dar and I'm really positively impressed. It solves a
>    bunch of problems I used to have w/ my scripts built on tar.
> 
>    What I would like to better understand is the way dar recognizes if a
>    file is to be backed up in incremental backups. Namely, does it use dim
>    and timestamp or does it compute som hash function. Does it need to read
>    it all *before* deciding whether to backup?

a file is defined to be "changed" since backup of reference if its inode 
  has changed: that's it if its permission changed or last modification 
date changed (last acces time and last inode change time are not 
compared) or ownership changed (unless -O is specified on command-line) 
or if its type has changed (file, named pipe, socket, char device, block 
device, directory, ...). If this is a plain file, the size of the file 
is also check for changes. If this is a symbolic link, the file pointed 
to, is also checked for change.

If all this stay identical a file is considered as unchanged. If by some 
manipulations you change a file contents without changing its size and 
set back the last modification time to what it was originally, dar will 
not know the file has changed.

> 
>    I ask this becouse I want to implement some network backup, ie saveing to
>    a remote box that is reachable only via an adsl line, so I wanted to know
>    how much information must be transferred over the internet.


> 
>    Is this already explained in some document that I missed?

In doc/FEATURE looking for "REMOTE OPERATION" will bring you all the 
informational pointers about that feature.

> 
>    Thanks for dar, thanks for your help

Thanks for feedback, you are welcome.

> 
>    sandro
>    *:-)
> 
> 
> 

Denis.
;-)



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