In reality, we don’t need to do a “full” backup each time we backup our servers, we can do “differential” backups.  Differential backups are basically backups of of all the changes since the last “full” backup.  In other words, only the difference since the last “full” backup.

A simple script to do differential backups for users’ home directory from Monday to Thursday and full backups on a Friday is as below.

#!/bin/bash
if [ `date +%w` -eq 5 ] ; then
if tar -cf /tmp/bck-full-`date +%F`.tar /home ; then
touch /var/log/bck/last-bck
tar -tf /tmp/bck-full-`date +%F`.tar > \
/var/log/bck/bck-`date +%F`.log
else
mail -s “Backup failed” root < ~
fi
elif [ `date +%w` -gt 0 ] && [ `date +%w` -lt 5 ] ; then
find /home -type f -newer /var/log/bck/last-bck | \
tar -cf /tmp/bck-diff-`date +%F`.tar -T -
if [ $? ] ; then
tar -tf /tmp/bck-diff-`date +%F`.tar > \
/var/log/bck/bck-`date +%F`.log
else
mail -s “Backup failed” root < ~
fi
fi

Of course, you will need to ensure that those directories used are already there and run the backups as root.  (Note, script edited to fit the width of this posting, so if you have errors, please leave a comment).

Post from: Suse & OpenSuse Tips
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Differential backup script sample

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