Is it permissible to run a shell script, which has commands like:

echo "Installing Development Tools"
yum $YUMOPTS groupinstall "Development Tools"
echo "Installing other packages"
yum $YUMOPTS install python-devel.i386
yum $YUMOPTS install postgresql84-server.i386 postgresql84-devel.i386 postgresql84-python.i386

# note: check install script that already exists. ask kamal.
# Download and install other packages
echo "Installing Asterisk"
wget http://downloads.asterisk.org/pub/telephony/asterisk/releases/asterisk-10.2.1.tar.gz
tar xvzf asterisk-10.2.1.tar.gz
cd asterisk-10.2.1
make install
chkconfig asterisk on

in the %post  section ?