備份說明: 1.所有的資料庫都要備份
                  2. 五天一個循環
                  3.備份在原本機器的硬碟上
 位置說明:      備份的目錄是DBbackup
                        底下子目錄需要自己去建立(只要一次0~4)
                       backup.0->>永遠是最新的備份資料
                       backup.1->>永遠是前一天的資料以此類推
這個是拿別人的shell來改的不是完全自己弄出來的,出處如下:
# ----------------------------------------------------------------------
# This is a free shell script under GNU GPL version 2.0 or above
# Copyright (C) 2006 Sam Tang
# Feedback/comment/suggestions : http://www.real-blog.com/
# ----------------------------------------------------------------------
底下是SHELL主要的內容:
#!/bin/sh
# mysql_backup.sh: backup mysql databases and keep newest 5 days backup.
#
# Last updated: 20 March 2006
# ----------------------------------------------------------------------
# This is a free shell script under GNU GPL version 2.0 or above
# Copyright (C) 2006 Sam Tang
# Feedback/comment/suggestions : http://www.real-blog.com/
# ----------------------------------------------------------------------

# your mysql login information
# db_user is mysql username
# db_passwd is mysql password
# db_host is mysql host
# -----------------------------
db_user="root"
db_passwd="vcqdru6u!@#map"
db_host="localhost"

# the directory for story your backup file.
backup_dir="/home/DBbackup"

# date format for backup file (dd-mm-yyyy)
time="$(date +"%d-%m-%Y")"

# mysql, mysqldump and some other bin's path
MYSQL="$(which mysql)"
MYSQLDUMP="$(which mysqldump)"
MKDIR="$(which mkdir)"
RM="$(which rm)"
MV="$(which mv)"
GZIP="$(which gzip)"

# check the directory for store backup is writeable
test ! -w $backup_dir && echo "Error: $backup_dir is un-writeable." && exit 0

# the directory for story the newest backup
test ! -d "$backup_dir/backup.0/" && $MKDIR "$backup_dir/backup.0/"

# get all databases
all_db="$($MYSQL -u $db_user -h $db_host -p$db_passwd -Bse 'show databases')"

for db in $all_db
do
        $MYSQLDUMP -u $db_user -h $db_host -p$db_passwd $db | $GZIP -9 > "$backup_dir/backup.0/$time.$db.gz"
done

# delete the oldest backup
test -d "$backup_dir/backup.5/" && $RM -rf "$backup_dir/backup.5"

# rotate backup directory
for int in 4 3 2 1 0
do
        if(test -d "$backup_dir"/backup."$int")
        then
                next_int=`expr $int + 1`
                $MV "$backup_dir"/backup."$int" "$backup_dir"/backup."$next_int"
        fi
done

exit 0;


shutdown -r now