首先输入打开终端输入su，输入密码，取得管理员权限；
其次输入 gedit /etc/yum.repos.d/163.repo,回车
再次把一下内容复制到打开的163.repo中：
[Fedora-mirrors.163.com]
name=Fedora 12 – i386
baseurl=http://mirrors.163.com/fedora/updates/12/i386/
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Fedora file:///etc/pki/rpm-gpg/RPM-GPG-KEY
[Everything-mirrors.163.com]
name=Everything 12 – i386
baseurl=http://mirrors.163.com/fedora/updates/12/i386/
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Fedora file:///etc/pki/rpm-gpg/RPM-GPG-KEY
[updates-mirrors.163.com]
name=Fedora updates
baseurl=http://mirrors.163.com/fedora/updates/12/i386/
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Fedora file:///etc/pki/rpm-gpg/RPM-GPG-KEY
保存，关闭163.repo最后，在终端中输入yum makecache，Fedora 12添加163源 成功了！