我正在尝试在装有 Ubuntu 14.10 的远程机器上安装 x2go 服务器。这就是我尝试这样做的方式：
apt-add-repository ppa:x2go/stable
apt-get update
apt-get install x2goserver x2goserver-xsession
在最后一行代码之前一切都很顺利，它输出：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package x2goserver-xsession is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
Package x2goserver is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'x2goserver' has no installation candidate
E: Package 'x2goserver-xsession' has no installation candidate
我只想使用安装在我的个人计算机上的 x2goclient 连接远程机器。
任何人都知道如何解决这个问题？