为什么“apt-get autoremove sendmail”会留下依赖项？

Question

我注意到安装 sendmail，然后卸载它，使用 apt-get 会留下许多不需要的文件。

sudo apt-get install sendmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  liblockfile-bin liblockfile1 make procmail sendmail-base sendmail-bin
  sendmail-cf sensible-mda
Suggested packages:
  make-doc sendmail-doc rmail logcheck resolvconf sasl2-bin
Recommended packages:
  default-mta mail-transport-agent fetchmail
The following NEW packages will be installed:
      liblockfile-bin liblockfile1 make procmail sendmail sendmail-base
      sendmail-bin sendmail-cf sensible-mda
0 upgraded, 9 newly installed, 0 to remove and 0 not upgraded.
Need to get 2256 kB of archives.
After this operation, 5263 kB of additional disk space will be used.
Do you want to continue? [Y/n] y

所以我们安装了 sendmail - 9 个新软件包和 5.2MB。
几分钟后，我改变了主意，想卸载它。没问题，apt-get 帮我解决了，对吧？我清除（删除包和包配置文件）：

sudo apt-get purge sendmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  procmail sensible-mda
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  sendmail*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 219 kB disk space will be freed.
Do you want to continue? [Y/n] y

然后autoremove（删除自动安装的包依赖）

sudo apt-get autoremove sendmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'sendmail' is not installed, so not removed
The following packages will be REMOVED:
  procmail sensible-mda
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 550 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 24702 files and directories currently installed.)
Removing sensible-mda (8.14.4-8+deb8u1) ...
Removing procmail (3.22-24) ...
Processing triggers for man-db (2.7.0.2-5) ...

回收了 219 + 550 = 769KB！我是否刚刚失去了 4.something MB 的空间？为了什么？

仔细查看输出后，apt-get 似乎只删除了之前自动安装的 3 个包。例如，包 sendmail-base 仍然是：

sudo apt-get remove sendmail-base
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  sendmail-base sendmail-bin
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 2464 kB disk space will be freed.
Do you want to continue? [Y/n]

所以我浪费了一些空间。但是为什么这些自动安装的依赖项仍然安装？

Answer 1

sendmail 是由一组依赖项组成的元包。当您安装 sendmail 元数据包时，它会安装 sendmail-bin 等。例如，这为 cron 提供了推荐的包，但我相信还有一些其他包推荐了 sendmail 依赖链中的包。

Autoremove 不会删除其他软件包推荐的自动软件包。例如，您可以通过添加此 apt 配置来更改此行为/etc/apt/apt.conf.d/99_norec

APT::AutoRemove::RecommendsImportant "false";
APT::AutoRemove::SuggestsImportant "false";

然后运行apt-get remove --auto-remove sendmail，您应该会看到所有与 sendmail 相关的包都被标记为要删除，以及一些其他不相关的东西，由于 apt 配置的整体更改，这些内容现在是删除的候选对象。

不过，我认为不推荐这样做（没有双关语）。如果您需要摆脱它们，您应该手动处理它们。