我正在将 Kubuntu 18.04 更新到 20.04 LTS，如下所示本教程的说明。
当我讲到这个部分时：
sudo do-release-upgrade
我收到一个错误，导致系统升级暂停。这是控制台中的错误堆栈：
Third party sources disabled
Some third party entries in your sources.list were disabled. You can
re-enable them after the upgrade with the 'software-properties' tool
or your package manager.
To continue please press [ENTER]
Hit http://nl.archive.ubuntu.com/ubuntu focal InRelease
Get:1 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Hit http://nl.archive.ubuntu.com/ubuntu focal-updates InRelease
Hit http://nl.archive.ubuntu.com/ubuntu focal-backports InRelease
Fetched 114 kB in 0s (0 B/s)
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating the changes
Calculating the changes
Could not calculate the upgrade
An unresolvable problem occurred while calculating the upgrade.
This was likely caused by:
* Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.
If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
=== Command detached from window (Fri Dec 24 10:56:10 2021) ===
=== Command terminated with exit status 1 (Fri Dec 24 10:56:20 2021) ===
但是，禁用第三方软件包的列表如下：
$> grep disabled /var/log/dist-upgrade/main.log
显示相关软件如Postgres（及其数据库）或 QGIS 都在那里。因此，我无法使用 ppa-purge 卸载这些软件包，因为重要数据存储在那里，我不能冒丢失任何内容的风险。但似乎我也无法升级系统。
我能做些什么来缓解这些情况？
答案1
postgresql 自 2012 年以来一直存在同样的问题。
2012 年发布了以下错误报告 Bug #996916：删除黑名单中的 postgresql 软件包导致难以升级，但没有真正的解决方案。
我建议备份您的数据库，然后删除所有与 postgress 相关的包，升级，重新安装包，最后返回数据库。