Re: Monitor ongoing upload?

[Colin Percival <cperciva@tarsnap.com>]

On 06/29/14 12:26, Jamie Landeg-Jones wrote:
>> If I copy a snapshot off to another device or tar file, and then
>> tarsnap off of that, will the transfer-only-changes feature still work
>> when I do subsequent tarsnaps of the original data?
> 
> There is an option to control this. From the man page:
> 
>  | --snaptime file
>  |              (c mode only) This option MUST be specified when creating a
>  |              backup from a filesystem snapshot, and file must have a modifica-
>  |              tion time prior to when the filesystem snapshot was created.
>  |              (This is necessary to prevent races between file modification and
>  |              snapshot creation which could result in tarsnap failing to recog-
>  |              nize that a file has been modified.)

This isn't really necessary for the case of "copy files to a different
device" -- it's specific to the case of filesystem snapshots (as in UFS
and ZFS) because those will keep the timestamps from the underlying file
system.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid