merge ‐ merge incremental dumps onto full dumps for restore

     merge <output file> <full dump> <incremental dump>

     merge is a utility that allows one to apply incremental dumps to a full
dump and produce a new full dump which reflects a later state of the volume.
The new dump can then be used to restore the volume, or can be merged with other

     An incremental or full dump reflects the state of the volume at the time it
was dumped. Full dumps can be restored so that a user may access an older state
of a volume. Incremental dumps do not necessarily have sufficient information to
be restored. For instance, all the vnodes in the dump may not be present. The
merging process allows a full image of a state that was only incrementally
dumped to be restored.

     Currently incrementals apply to the last successful full dump that was
done.  As an example, say full dumps for a volume are done on Sundays, with
incrementals being taken the rest of the week. If an administrator wishes to
restore a volume to Wednesdays state, he would have to fetch the full dumpfile
from Sunday and the incremental dumpfile for Wednesday. Once these are present,
the administrator would use the merge program to create a new updated full dump
for Wednesdays state, and restore it to the server (using volutil(8) restore).

     Information in the dump header is used to place a total ordering on the
dumps. This way incrementals can only be applied to the dump with repect to
which they were taken. In addition, incrementals cannot be applied to other
incrementals, and the dumps to be merged must have been created from the same
volume replica. The merge program checks these things, and reports failures if
they are violated.

     volutil (8), restore (1)


     David C. Steere, 1991, created