[geeks] Linux tape backup help

[der Mouse]

> So I need to know 2 things:

> 1. How to append to a rewound tape.

mt fsf N, where N is the number of files on the tape, then write.  Or,
if you want to append to a single tape file, mt fsr N where N is the
number of records on the tape.

At least, assuming the tape fits the usual Unix tape model.  Not all
tapes do (eg, quarter-inch cartridges); you say "LTO3", but I don't
recognize that enough to say anything useful about it.  Might be worth
experimenting with a scratch tape.

> 2. How to determine the size of a backup (full and incremental) and
> of space exists on the tape to store it.

Size?  You'll have to deal with your backup software for that.  Some of
them can give you estimates, of varying degrees of accuracy.  (You say
"tar", but there are many variants of tar, with disparate
capabilities.)

It's relatively easy to figure out how big the backup was, ie, after
the fact, but for this you want to know how big it will be, ie, before
the fact.  Historical data might be enough, but also might not - I
don't know enough about your environment.

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