Re: bin/52432: /etc/dumpdates format egregious

[Robert Elz <kre%munnari.OZ.AU@localhost>]

The dumpdates file (and all associated with it) needs lots of work.
It is close to hopeless when dumping filesystems on wedges (what good is
it knowing that /dev/dk3 was last dumped... when dk3 might be something
entirely different when the next dump happens.)

What's more, it dates back to the days when dumps were all done to tape,
and there would be one set of tapes for each filesystem, and (provided
that one can map device names to filesystems) it worked OK for keeping
track of what had been dumped where.

These days, I'd guess that more people do dumps like I do, onto a removable
USB drive - each one of those can handle lots of dumps, for many filesystems,
and for many dump cycles ... but doing just that means that there's not
a lot of redundancy (in the tape days, if a tape was found to be bad when
a filesystem restore was needed, you simply picked the next most recent,
usually the day before...)

I have a bunch of USB drives I dumps to, and to make that rational, each
has its own dump sequence (so I do a full (level 0) dump, then some
incrementals, then another full dump, ...) but not to the same device each
time, I flip around which drive I am using so no one gets used twice in a
row, so if one of those fails, there's always the other one, or another...

To make that work with dump as it is, my script has to look and see which
dumpdates file is in /etc and if it is the wrong one, copy the one that
belongs to the dump sequence for the output device being used for this set
of dumps ... it would be much simpler if I could just tell dump where the
dumpdates file is located .. and then use the one in /etc merely to keep
track of the last dumps for each filesystem, not for working out which date
to go back until when doing an incremental dump (ie: provide the data for
dump W to use, and nothing else.)

I have been meaning to propose some radical work on dumpdates for ages.

I do not buy the "it is the API" for a second, the only thing that uses
dumpdates is dump (restore doesn't) change dump (keep it able to read the
old format) and we can make the dumpdates file contain any format that
makes sense, which the current one does not.

kre