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The map usedinomap is a list of inodes that have been deleted since the last dump. restore uses this map to delete files before doing a restore of files in this dump. The map dumpinomap is a list of all inodes contained in this dump. Each header contains a lot of information:
Logical block of record
Number of records to follow
Name of dumped filesystem
Name of dumped device
Name of dumped host
First record on volume
Map of inodes deleted since last dump
Map of inodes in dump
Beginning of file record
Continuation of file record
End of volume marker
When dump writes the header, it includes a copy of the inode for the file or directory that immediately follows the header. Since inode data structures have changed over the years, and different filesystems use slightly different inode data structures for their respective filesystems, this
As long as all dump programs do this, then you should be able to restore the data on any Unix system that expects the inode data structure to be in the old BSD format. It is for this reason you can interchange a dump volume written on Solaris, HP-UX, and AIX systems.
This was first published in August 2007