我想使用TensorFlow在 Ubuntu 16.04 上，需要 CUDA 9.0，而不是最新的 9.1。不过，我之前已经安装了 CUDA 9.1。运行
sudo apt-get remove --purge cuda* && sudo apt-get autoremove
我确认其中/usr/local没有cuda文件夹。然后，我按照nvidia 说明使用 安装 CUDA 9.0 .deb。但是，当我 时sudo apt-get install cuda，确认消息以以下内容开头：
The following NEW packages will be installed:
cuda cuda-9-1 ...
以及其他对 CUDA 9.1 的引用。
问题：为什么要安装这个 9.1 版本？它从哪里链接来的？
如果有帮助的话，以下是 的输出apt-key list：
/etc/apt/trusted.gpg
--------------------
pub 1024D/437D05B5 2004-09-12
uid Ubuntu Archive Automatic Signing Key <[email protected]>
sub 2048g/79164387 2004-09-12
pub 4096R/C0B21F32 2012-05-11
uid Ubuntu Archive Automatic Signing Key (2012) <[email protected]>
pub 4096R/EFE21092 2012-05-11
uid Ubuntu CD Image Automatic Signing Key (2012) <[email protected]>
pub 1024D/FBB75451 2004-12-30
uid Ubuntu CD Image Automatic Signing Key <[email protected]>
pub 1024D/7FAC5991 2007-03-08
uid Google, Inc. Linux Package Signing Key <[email protected]>
sub 2048g/C07CB649 2007-03-08
pub 4096R/D38B4796 2016-04-12
uid Google Inc. (Linux Packages Signing Authority) <[email protected]>
sub 4096R/640DB551 2016-04-12 [expires: 2019-04-12]
sub 4096R/997C215E 2017-01-24 [expires: 2020-01-24]
pub 4096R/48457EE0 2016-05-24 [expires: 2018-05-24]
uid Bazel Developer (Bazel APT repository key) <[email protected]>
sub 4096R/43FF45F9 2016-05-24 [expires: 2018-05-24]
pub 4096R/7FA2AF80 2016-06-24
uid cudatools <[email protected]>
/etc/apt/trusted.gpg.d/graphics-drivers_ubuntu_ppa.gpg
------------------------------------------------------
pub 4096R/1118213C 2015-08-12
uid Launchpad PPA for Graphics Drivers Team
/etc/apt/trusted.gpg.d/webupd8team_ubuntu_atom.gpg
--------------------------------------------------
pub 1024R/EEA14886 2010-05-04
uid Launchpad VLC