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  Backups on CD
Chapter 1 Overview
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1.1 Usage

Just type backuponcd -s (directory) -e (excludelist), where (directory) is the full path to the directory which you want to archive and (excludelist) is a grep-script.

The output of backuponcd -h is:

     -s directory which is to archived
     -e excludelist may be a empty file, usually a list of mountpoints,
        view example in /etc/backuponcd/excludelist
     -a archiver (optional) overrides your setting (archiver=..)
        in /etc/backuponcd/global.rc
     -rc global settings (optional).
         Overrides built in parameter "-rc /etc/backuponcd/global.rc".
         Must be full path to rc file.

If you want to generate a backup on a running system, some folders must be excluded, have a look on an example exclude list (see /usr/doc/backuponcd/samples/excludelist, Section 4.1).

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1.2 What does it do?

The script generates a backup providing tar or afio relative to (directory) and stores it temporary in the backuppath, depending on your settings in /etc/backuponcd/global.rc, Section 4.2. The archive can have any length, it is splitted into smaller pieces and burned while the backup runs continuous.

This is done by using pipes and burning multisession CDs, so don't worry if the gzipped tarball of your system amounts 1.5 + Gbyte. In this case you need 3 CDs with a media cost of 6$ if you use CD-RW.

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1.3 How does it work?

Extracting an archive looks like this:

     cat /cdwriter/tar.gz.* | tar --compare --gzip --file=- | \
     tee -a /tmp/logfile

while the filenames of the archive are tar.gz.00, tar.gz.01 and so on.

A bit more complicated is reading a multisession backup:

     # /usr/doc/backuponcd/samples/simple_read
     # a very simple example how to read an archive stored on
     # several CDs. Must be killed by typing ^C if reading is
     # finished.
     device="0,3,0"
     rawdevice=/dev/cdrom
     mountpt=/cdrom
     
     while true; do
       cdrecord dev=$device -eject > /dev/null 2>&1
       echo -e "\a\n Please insert the (next) volume" > /dev/tty
       read ans
       mount -t iso9660 -o ro,noexec $rawdevice $mountpt
       if test $? -eq 0; then
         echo "Now reading the volume..." > /dev/tty
         cat /cdrom/*gz*
       else
         echo -e "\a\n Mount failed." > /dev/tty
       fi
       umount $mountpt
     done 2> /dev/tty < /dev/tty

The script is used as follows:

     ~/bin/simple_read | tar --compare --gzip --file=- | \
     tee -a /tmp/logfile

BackupOnCd comes with longer shell scripts which recognize multi- and singlesession CD and type out better comments, know which volume is inserted and so on.

If you assume that burning does work similar you're right, it does (see Details, Chapter 3 if you are interested).

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Abstract Copyright Contents next
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Backups on CD
17 April 2000
Holger Nassenstein backups@tuxoncd.de
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