To install Mambo 4.5.1 RC3 Follow the following steps:
$cd /home/..../your_mambo_folder
$wget
http://mamboforge.net/frs/download.p....1-RC-3.tar.gz
$tar -xvzf MamboV4.5.1-RC-3.tar.gz
####### Change folder permission #######
$chomd 707 /your_mambo_folder/
$chomd 707 /administrator/backups
$chomd 707 /administrator/components
.
.
.
$chomd 707 /...
Run the web installer, That's it
