16.04 LTS 到 18.04.1 LTS 升级：未找到新版本

Question

我无法将 16.04 LTS 升级到 18.04.1 LTS，我正在运行服务器。

我现在的版本：

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.5 LTS
Release:    16.04
Codename:   xenial

然而，尽管 18.04.1 于 7 月 26 日发布，但目前在 31 日我仍然被告知没有新版本？

我的/etc/update-manager/release-upgrades文件是：

# Default behavior for the release upgrader.

[DEFAULT]
# Default prompting behavior, valid options:
#
#  never  - Never check for a new release.
#  normal - Check to see if a new release is available.  If more than one new
#           release is found, the release upgrader will attempt to upgrade to
#           the release that immediately succeeds the currently-running
#           release.
#  lts    - Check to see if a new LTS release is available.  The upgrader
#           will attempt to upgrade to the first LTS release available after
#           the currently-running one.  Note that this option should not be
#           used if the currently-running release is not itself an LTS
#           release, since in that case the upgrader won't be able to
#           determine if a newer release is available.
Prompt=lts

和输出do-release-upgrade：

Checking for a new Ubuntu release
No new release found.

更新管理器核心已安装：

sudo apt install update-manager-core
Reading package lists... Done
Building dependency tree       
Reading state information... Done
update-manager-core is already the newest version (1:16.04.13).
0 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.

请注意，此问题与此处的问题不同。是否应向我提供升级到 18.04.1 的选项？因为该问题涉及基于 GUI/桌面的情况，而这专门从终端/服务器角度解决了该问题。

Answer 1

预计8 月初发布 18.04.1 后几天，才会启用 16.04 LTS 的升级。 https://wiki.ubuntu.com/BionicBeaver/ReleaseSchedule