I did tar archive...how to update?

I did tar archive...how to update?

Post by Ryan M. Hans » Tue, 19 Nov 1996 04:00:00


I just did a simple backup of my home linux box w/ tar (multiple floppy),
just to aid me in helping me get back up to exactness if I ever need to
reinstall or I*something up bad!

tar -cvMf /dev/fd0 /etc /usr/local /home/rmhanson /usr/src/patches

(think of anymore?)

anyways now How do I update it w/o rewriting the whole thing over?
I know there is the d and u tar flags but have not been able to figure the
stupid things out! "dumped" message?

can any of you linux gurus show me how? thanx.

Version: 2.6.2



I did tar archive...how to update?

Post by Nat Makarevitc » Mon, 02 Dec 1996 04:00:00

Quote:Ryan M Hanson writes:
> I just did a simple backup of my home linux box w/ tar (multiple floppy)
> tar -cvMf /dev/fd0 /etc /usr/local /home/rmhanson /usr/src/patches
> /usr/bin/slrn
> (think of anymore?)
> anyways now How do I update it w/o rewriting the whole thing over?

by a brutal method, using "find" in order to save only, on a new backup
set, modified or created files.
for example:
find /etc -mtime -9 -daystart -type f > /tmp/to_be_saved
find /usr/local -mtime -9 -daystart -type f >> /tmp/to_be_saved
 ... and so on ...

tar -cvM -T /tmp/to_be_saved -f /dev/fd0

but file deleted will not be erased after a restore operation.

best: by using the "-g" option of tar.
tar -g /tar_listed_incremental_trace -cvM -f /dev/fd0 /etc /usr/local ...

Nat    Linux


1. TAR archive updating

Hey all,

I was wondering if any of you have ever experienced a similar problem:

I'll start out by saying that I am by no means a Unix or Linux expert.  I've
used such systems for development for a few years, but in that time I never
got down into some of the nitty-gritty of the various commands (i.e., TAR)
and their relation to physical devices.  Currently, I'm trying to write a
Perl script that will automate tape backups for a real time data feed.  I've
figured out, on an algorithmic basis, what TAR does when creating files on
the disk, but it doesn't seem to carry over to tapes.  I can use the 'tar
cvf' command to create an archive on the tape drive.  If the files are small
enough (I think) then I can use the 'tar rvf' command to update the archive
with new files.  However, after I've done this I can never get 'tar rvf' to
work on the same tape with the preexisting archive again.  It seems like
there is no space left on the tape to write a record of what is being stored
in the archive, so it won't let me write any more files.  It gives me an I/O
error instead.  Here is what the final session looks like, after I've
already added some files to the archive and checked for their presence with
'tar tvf':

devel/chris> tar rvfb /dev/rmt/0 5 test1.chris
a test1.chris 1 tape blocks
tar: tape write error

If anyone has any information on blocking factors, limitations of TAR with 8
mm tapes, good places to look in mtio, or something similar, please email me

a lot of time and it shouldn't be so hard to add files to an archive just
because they exceed some default size.  Thanks.


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