yum的若干问题及错误，请执教！

cupid

我的系统是FC3，yum.conf文件如下：
[main]
cachedir=/var/cache/yum
debuglevel=2
logfile=/var/log/yum.log
pkgpolicy=newest
distroverpkg=redhat-release
tolerant=1
exactarch=1
retries=20
obsoletes=1
gpgcheck=1
proxy=http://210.29.96.35:80

[geekbone]
name=geekbone Fedora Core $releasever - $basearch - Base
baseurl=http://mirrors.geekbone.org/fedora/core/$releasever/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora

[geekbone extras]
name=geekbone Fedora Extras $releasever - $basearch
baseurl=http://mirrors.geekbone.org/fedora/extras/$releasever/$basearch/
mirrorlist=http://fedora.redhat.com/download/mirrors/fedora-extras-$releasever
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-extras
gpgcheck=1


1、RPM-GPG-KEY-fedora-extras这个文件是我在网站上下的，然后放在/etc/pki/rpm-gpg目录下，不知道这样对不对？ 后来查到资料好像是要rpm --import key，请问这里的key到底有什么作用啊？

2、yum list出现错误如下：
[root@localhost ~]# yum list
Setting up Repo: geekbone extras
repomd.xml 100% |=========================| 951 B 00:00
Setting up Repo: base
Cannot find a valid baseurl for repo: base
这是怎么回事啊？好像是找不到有效的baseurl，应该怎么解决啊？ 可是看输出的话，geekbone extras有效了，可是base无效？

3、yum.conf中proxy好像不起作用，只能export http_proxy=....才可以。

谢谢！