Under certain circumstances, Tarsnap will interrupt the creation of an archive. When this occurs, the archive's name will have ".part" appended, to denote that it is a "partial" archive, and a new archive cannot be given the same name as the original (attempted) archive.

Partial archives can arise from:

• The user presses ^Q or sends a SIGQUIT.
• Tarsnap fails while creating an archive (e.g., due to a power failure or loss of internet connectivity) but later recovers a checkpoint.
• The bandwidth limit --maxbw is reached.

Partial archives count towards deduplication: If you attempt to create a new archive from the same data, Tarsnap will not upload any data that is already covered by that partial archive, thereby allowing us to minimize wasted bandwidth.

"Completing" a partial archive

For example, suppose we wish to have a series of daily archives, but today's archive is interrupted. For simplicity, suppose that today is January 3rd, 2016.

tarsnap --list-archives
backup-2016-01-01
backup-2016-01-02
backup-2016-01-03.part

To "complete" the partial archive, we would create a new archive as normal, albeit with a new name:

tarsnap -c -f backup-2016-01-03-second /MY/DATADIR

If we created the backup-2016-01-03-second archive successfully, then we can delete the partial archive and rename the new one to match our naming scheme:

tarsnap -d -f backup-2016-01-03.part

tarsnap -c -f backup-2016-01-03 @@backup-2016-01-03-second

tarsnap -d -f backup-2016-01-03-second

We will now be left with the archives we desired:

tarsnap --list-archives
backup-2016-01-01
backup-2016-01-02
backup-2016-01-03