advantage of 'mt'?
2007-12-25 11:55:00
For the most part I heard that either on was good, but the ufsrestore
with the 's' switch will only work if you are at the beginning of the
tape.
Here are some of the responses:
Thanks,
Dave Parker
=============================================================================
I have found that the ufsrestore switch is sometimes confused for no
aparent reason. We proved this with a lab at a Sun course I took in NY
last year.
I also use ufsdump with many files on one tape. Typically, I will set
up a text header on the tape with a table of contents. Mine is very
complicated, but you could set one up such as this:
FS Host Volume
1 hosta /
2 hosta /usr
3 hosta /var
4 hosta /export
5 hostb /
6 hostb /export/share0
7 hostb /export/share1
8 hostb /export/share2
Then, I will put in the tape and 'cat /dev/rmt/0n' to be sure I have the
right tape. If I want to restore from /export/share0 on hostb, I will
do this:
# mt -f /dev/rmt/0n asf 6
# ufsrestore ivf /dev/rmt/0n
The 'asf' command will space to the *absolute* file system. The first
file, the table of contents, is file ZERO.
Best,
Sal Serafino
=====================================================
No difference whatsoever if you're at the start of the tape.
If you need to do more complicated things (like skip back 2 dumps), then
you'll need mt.
David Mitchell
======================================================
You can't use "ufsrestore" when on tape are present backups that are not
created with "ufsdump". With "mt" you can browser the beginning of each
volume present on tape, go to on the last volume (option "eom") for
appending another volume and so on.
On my daily task the machines make a backup on tapes, and each time one
of that is done, the script append information where the backup are
present on tape (tape and position).
However, the two option ("mt" and "ufsrestore") are identical, for your
pourpose.
Hope this help.
Cesare
================================================================
I have found the 's' option from ufsrestore to be a bit flaky for some
reason. One real problem with it is that it will only do relative skips
(i.e. skip forward n tape files). I like to use the 'asf' mt command to
put me at the tape file I want rather than trying to remember which tape
file I am up to and calculating a diff between where I am and where I am
going.
Brett Lymn
==================================================================
No functional difference - I usually use the ufsrestore switch for
simplicity.
Ian MacPhedran
==================================================================
My guess is that those that use `mt' are using scripts that date from
before the arrival of the `-s' option on restore. I must admit that
when it comes to data recovery, I'm an out-and-out control freak and I
like a stage-by-stage approach, so I use `mt'. Does `-s' get you a
progress report as it skips?
Ultimately I don't see it making much difference, though, no.
Sam Nelson
=================================================================
Original Message: Dec. 19, 2000
Hi guys, just a quick question. I am trying to backup multiple
filesystems onto one tape. I would like to know if when restoring the
filesystems, it's better to use 'mt' to skip to a volume and then use
ufsrestore, or using ufsrestore with a 's' option? I've seen a lot of
examples where they use 'mt', is there a difference one way or the
other?
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