点版本升级：无法将 Ubuntu 14.04.1 更新至 14.04.2

Question

非常简单的问题，但目前桌面上安装的 Ubuntu 版本是 Ubuntu 14.04.1 LTS，已通过验证

sanchit@sanchit-Home:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.1 LTS
Release:    14.04
Codename:   trusty

然后，

sanchit@sanchit-Home:~$ sudo apt-get dist-upgrade 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sanchit@sanchit-Home:~$ 

为什么不升级？