我是 Ubuntu 操作系统的新手。我试图从版本 14.04 升级到 16.04。但无法升级到最新版本。
下面是我在升级时收到的消息，因此我使用以下方法对 sources.list 进行了更改http://repogen.simplylinux.ch。
Could not calculate the upgrade
An unresolvable problem occurred while calculating the upgrade.
This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu
但是 sources.list 文件没有正确更新。该文件显示如下：
###### Ubuntu Main Repos
deb http://in.archive.ubuntu.com/ubuntu/ xenial main
deb-src http://in.archive.ubuntu.com/ubuntu/ xenial main
###### Ubuntu Update Repos
deb http://in.archive.ubuntu.com/ubuntu/ xenial-updates main
deb-src http://in.archive.ubuntu.com/ubuntu/ xenial-updates main
:wq
:wq!
:wq
我原来的 sources.list 文件是这样的：
# deb cdrom:[Ubuntu 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20140722.2)]/ trusty main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://in.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://in.archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse #Added by software-properties
## Major bug fix updates produced after the final release of the
## distribution.
deb http://in.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://in.archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse #Added by software-properties
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ trusty universe
deb http://in.archive.ubuntu.com/ubuntu/ trusty-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://in.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://in.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://in.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse #Added by software-properties
deb http://in.archive.ubuntu.com/ubuntu/ trusty-security main restricted
deb-src http://in.archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse #Added by software-properties
deb http://in.archive.ubuntu.com/ubuntu/ trusty-security universe
deb http://in.archive.ubuntu.com/ubuntu/ trusty-security multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu trusty partner
deb-src http://archive.canonical.com/ubuntu trusty partner
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu trusty main
deb-src http://extras.ubuntu.com/ubuntu trusty main
# deb http://www.rabbitmq.com/debian/ stable main
# deb http://downloads.sourceforge.net/project/sonar-pkg/deb trusty main
deb http://in.archive.ubuntu.com/ubuntu/ trusty-proposed restricted main universe multiverse
面临升级和不正确更改的问题。