Multiple Volumes with tar

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Newsgroups: comp.os.linux.misc
Date: Sat, 08 Feb 2003 12:42:59 -0500

>what is the parameter to create multiple volumes with tar on disk - not on any
>tape drive.
>I want backup some directories and limit the filesize to 500mb for storing
>them on cdrw.

The multi-volume with tar kind of assumes you will be swapping tapes out; so what you need to do is create a script to "simulate" a tape switch by renaming files. You can manually rename the file to file1, etc, and let tar "think" you changed tapes.

Below is an example. The following example only counts to 10 correctly, but you can get the idea. The problem with tar multi-volume is that if you want to compress, you have to compress afterwards, and the results are not predictable to know how to fill a cd, etc. There is a backup solution called "dar", (do a google search); which will let you set a "compressed multi-volume size". It is worth checking out.

I have a better set of scripts which does this with perl, but I hate do distribute them because they are suited to my system, but if you want a copy, email me. My scripts count as high as you need, and break each directory into it's own backup, in case you need to restore just one directory. There are restore scripts too, which do the opposite function to reassemble the tar segments.

#!/bin/sh
#backup

if [ -z "$1" ]; then
  echo 'Usage: backup dir'
  exit 1
fi

PREFIX="mybackup"
tar -c -X EXCLUDE_FILE -M -L 500 -F backup-rotate.sh -f $PREFIX.tar $1

#this section tests for the last incomplete archive and renames it to
the last number
##################################################################################
#LASTNUM=`ls $PREFIX-*.tar | tail -1 | awk -F. '{print $1}' | awk -F-
'{print $2}'`
LASTNUM=`ls $PREFIX-*.tar | awk -F. '{print $1}' | awk -F- '{print $2}'|
sort -g | tail -1`

if [ X$LASTNUM = X ] ; then
NEWNUM="1"
else
NEWNUM=`expr $LASTNUM + 1`
fi

mv $PREFIX.tar $PREFIX-$NEWNUM.tar
#################################################################################

#this section gunzips all the tar files
#gzip *.tar
exit

And here is the backup-rotate.sh

#!/bin/sh
PREFIX="mybackup"

#LASTNUM=`ls $PREFIX-*.tar | tail -1 | awk -F. '{print $1}' | awk -F-
'{print $2}'`
LASTNUM=`ls $PREFIX-*.tar | awk -F. '{print $1}' | awk -F- '{print $2}'|
sort -g | tail -1`

if [ X$LASTNUM = X ] ; then
NEWNUM="1"
else
NEWNUM=`expr $LASTNUM + 1`
fi

mv $PREFIX.tar $PREFIX-$NEWNUM.tar

zentara

Multiple Volumes with tar

> > I have a better set of scripts which does this with perl, but
>
>hi, could you mail a copy to me please (and the restore script too)?
>That's something I've been looking for for a long time. thanks.

this is how they work. You run "do-backup root" or "do-backup home". They will tar and gzip all directories, and break them into small pieces, for easier copying. /usr is broken into it's sub-dirs since it's so big.

The homedirs are also broken into subdirs, AND all the hidden files and directories are saved into a separate directory "rootbacktemp", so when you restore, remember to copy them back to your homedir root.

When the cd's are make, 3 programs are copied to each cd, "restore,restore-rotate.pl, and microperl". microperl is a small version of perl, that allows you to restore from scratch, without a perl installation.

To restore, just copy all the files you want into a directory, along with "restore,restore-rotate.pl, and microperl". Then run restore. Everything will be automatic after that. These cd's are written as ext2, so if you boot with a rescue floppy, and try to mount the cd's to copy them in, use "mount -t ext2 /dev/hdc /mnt" (or whatever is right for you.)

The "cdwrite" script , way down at the bottom, has the setting for cdrecord. Use "cdrecord -scanbus" to get your dev, and put it in there. The dummy switch is for testing.

If you use the dummy switch, and keep inserting a blank cdr when prompted, you won't write any cd's but all the iso's will be created, in /.

This script isn't perfect, it requires that you have a good bit of free space on the hard drive for the iso's. The iso's are saved in /, but you could modify the script to delete each iso after it is written to cdr, if you are tight on space. There is a line in cdwrite which is commented out "#unlink image.iso". Just uncomment that line to delete isos after they are written.

I suggest using the dummy switch first, and see how it goes, if the iso's are created, then you are doing it right.

I tried to do some parallel processing in this script, so it will write and process the next iso at the same time. This is very cpu intensive, so it is best to do this when nothing else is happening.

The scripts run fine with a scsi cdwriter, I don't know if they behave well with ide-scsi.

Good luck, feel free to modify and use the scripts as you desire.

P.S. If you don't feel comfortable with running the binary "microperl" which I've include (I wouldn't run any binary sent to me); you can make your own or you can change the restore scripts to run with #!/usr/bin/perl

Microperl can be made from the perl5.8 distibution, with "make -f Makefile.micro".

These scripts run good once you understand them.

zentara