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
