freebsd-dev/tools/3.0-upgrade

By 1996/12/04, the utmp element size has been changed, in order to
allow for longer usernames.  This change renders all existing wtmp
files unusable.  The cvt-wtmp utility is provided as an aid to convert
your old wtmp files into the new format, so you don't lose the
existing track record.

The tool cannot handle gzip'ed wtmp backups, so unzip them first if
you need.  Then simply call it as:

	./cvt-wtmp /var/log/wtmp*

The old wtmp files are being renamed to <file>.bak, so nothing will be
lost even in case of a failure.  If you are only about to test whether
the tool will grok your files correctly, you can run it as:

	./cvs-wtmp -n /var/log/wtmp*

The tool tries an ``educated guess'', based on the reasonability of
the timestamp values in the wtmp file.  If it fails to recognize the
format of your wtmp, it normally bails out, or at least ignores
garbage records.  In this case, rename the .bak files to the original
name, and try to force the conversion:

	./cvs-tmp -f /var/log/wtmp.xxx

Make sure to verify the result however!


Dresden, Jan 2, 1996			Joerg  <joerg@freebsd.org>