yum groupinstall question

Hello,

I'm attempting to install RHEL packages to a directory with yum.
e.g)
# mkdir /tmp/rhel5.3
# yum -y --installroot=/tmp/rhel5.3 -c yum.conf --disablerepo=* \
--enablerepo=rhel5.3 install bash
# yum -y --installroot=/tmp/rhel5.3 -c yum.conf --disablerepo=* \
--enablerepo=rhel5.3 groupinstall "core"

my yum.conf is much simple. It just defines repo name and bseurl which is pointed to dvd.
[rhel5.3]
name=rhel5.3
baseurl=file:///media/rhel5.3/Server

When I run above "yum groupinstall" command, it failed due to a couple of
packages are already install below...

Transaction Check Error:
  package libtermcap-2.0.8-46.1 is already installed
  package glibc-2.5-34 is already installed
  package libgcc-4.1.2-44.el5 is already installed


Is this normal yum behavior? Please advise me.
I wonder if we could skip to install these installed packages.

BTW, only "yum groupinstall core" can't resolve dependency for "bash" correctly.
So, this is why I'm installing "bash" before "core" group.

"libtermcap" should be installed before the bash, but "yum groupinstall" didn't.
When I installed "yum install bash", it's fine.

Thanks
-Ihara