Debian dist-upgrade 删除 apache2

我正在运行一个带有一些 Web 应用程序的 Debian 8.11 (Jessie) 机器。现在我想使用在服务器上安装所有待处理的更新

apt-get-update
apt-get upgrade

这显示在屏幕上：

Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  apache2 apache2-bin apache2-data apache2-utils certbot libaugeas0 libssl1.1 python-cffi-backend python-cryptography python-openssl python-pbr python-psutil python-requests python-six python-urllib3
0 upgraded, 0 newly installed, 0 to remove and 15 not upgraded.

然后我想我可以继续使用

apt-get dist-upgrade

它首先产生了以下内容：

Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... The following package was automatically installed and is no longer required:
  apache2-data
Use 'apt-get autoremove' to remove it.
Done
The following packages will be REMOVED:
  apache2 libapache2-mod-php5 mailman mod-pagespeed-stable python-certbot-apache
The following packages have been kept back:
  certbot python-cffi-backend python-pbr python-psutil python-six python-urllib3
The following packages will be upgraded:
  apache2-data apache2-utils
2 upgraded, 0 newly installed, 5 to remove and 6 not upgraded.
Need to get 0 B/400 kB of archives.
After this operation, 69.2 MB disk space will be freed.
Do you want to continue? [Y/n]

选择“Y”后，我没有安装 apache web 服务器，也没有机会重新安装它。

我现在的问题：
- 这里发生了什么？
- 这是因为系统已经太旧了吗？
- 我可以做些什么来使用仍在工作的 apache Web 服务器（和所有其他服务）更新系统
- 如果可能，我还想升级到最新的 debian 版本

我看到了一些关于如何升级 Debian 的提示，但所有这些提示都必须完成 dist-upgrade 作为先决条件......

您的帮助将不胜感激。

最好的汤姆