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[Translated] tech/20200827 How to Check Dependencies of a Package in Ubuntu-Debian-based Linux Distributions.md

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[#]: collector: (lujun9972)
[#]: translator: (FSSlc)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (How to Check Dependencies of a Package in Ubuntu/Debian-based Linux Distributions)
[#]: via: (https://itsfoss.com/check-dependencies-package-ubuntu/)
[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/)
How to Check Dependencies of a Package in Ubuntu/Debian-based Linux Distributions
======
Installing applications via command line is quite easy in Ubuntu/Debian. All you need to do is to use apt install package_name.
But what if you want to know the dependencies of a package before or after installing it?
In this tutorial, I’ll show you various ways to see the dependencies of a package in Ubuntu and other Debian-based Linux distributions that use [APT package management system][1].
### What is package dependency in Ubuntu?
If you didn’t know already, when you install a software package in Linux, sometimes, it needs other packages to function properly. These additional packages are called dependencies. If these dependency packages are not installed on the system, it is usually installed automatically with the package.
For example, the [GUI tool HandBrake for converting video formats][2] needs [FFmpeg][3], [GStreamer][4]. So for HandBrake, FFmpeg and GStreamer are the dependencies.
If you don’t have these packages installed on your system, they will be automatically installed when you [install HandBrake on Ubuntu][5].
### Check dependencies of a package in Ubuntu and Debian based distributions
As it often happens in Linux, there are more than one way to achieve the same result. Let’s see various ways to see the dependencies of a package.
#### Checking dependencies with apt show
You can use the [apt show command][6] to display details of a package. Part of this information is dependencies and you can see it in the line starting with Depends.
For example, here’s what it shows for [ubuntu-restricted-extras][7] package.
```
[email protected]:~$ apt show ubuntu-restricted-extras
Package: ubuntu-restricted-extras
Version: 67
Priority: optional
Section: multiverse/metapackages
Origin: Ubuntu
Maintainer: Ubuntu Developers <[email protected]>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 14.3 kB
Depends: ubuntu-restricted-addons
Recommends: libavcodec-extra, ttf-mscorefonts-installer, unrar
Download-Size: 3,200 B
APT-Manual-Installed: yes
APT-Sources: http://us.archive.ubuntu.com/ubuntu focal/multiverse amd64 Packages
Description: Commonly used media codecs and fonts for Ubuntu
This collection of packages includes:
- MP3 and other audio codec software to play various audio formats
(GStreamer plugins)
- software to install the Microsoft Web fonts
- the Adobe Flash plugin
- LAME, software to create compressed audio files.
.
This software does not include libdvdcss2, and will not let you play
encrypted DVDs. For more information, see
https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs
.
These software packages are from the Multiverse channel, restricted by
copyright or legal issues in some countries. For more information, see
http://www.ubuntu.com/ubuntu/licensing
```
As you can see, ubuntu-restricted-extras package depends on ubuntu-restricted-addons package.
Here’s a catch! The dependency package may also depend on some other package and the chain could go on. Thankfully, the APT package manager handles this for you by automatically installing all the dependencies (most of the time).
What is recommended package?
Did you notice the line starting with Recommends in the above output?
Recommended packages are not direct dependencies for the package but they enable additional features.
As you can see, ubuntu-restricted-extras has ttf-mscorefonts-installer as recommended package for installing Microsoft Fonts on Ubuntu.
The recommended packages are also installed by default and if you explicitly want to forbid the installation of recommended package, use the –no-install-recommends flag like this:
sudo apt install –no-install-recommends package_name
#### Use apt-cache for getting just the dependencies information
The apt show has way too many information. If you want to get the dependencies in a script, the apt-cache command gives you a better and clean output.
```
apt-cache depends package_name
```
The output looks much clean, does it not?
![][8]
#### Check the dependencies of a DEB file using dpkg
Both apt and apt-cache command works on the packages that are available from the repositories. But if you download a DEB file, these command won’t work.
In this case, you can use the dpkg command with -I or –info option.
```
dpkg -I path_to_deb_file
```
The dependencies can be seen in the line starting with Depends.
![][9]
#### Checking dependencies and reverse dependencies with apt-rdepends
If you want more details on the dependencies, you can use the apt-rdepends tool. This tool creates the complete dependency tree. So, you get the dependency of a package and the dependencies of the dependencies as well.
It is not a regular apt command and you’ll have to install it from the universe repository:
```
sudo apt install apt-rdepends
```
The output is usually quite large depending on the dependency tree.
```
Reading package lists... Done
Building dependency tree
Reading state information... Done
shutter
Depends: procps
Depends: xdg-utils
imagemagick
Depends: imagemagick-6.q16 (>= 8:6.9.2.10+dfsg-2~)
imagemagick-6.q16
Depends: hicolor-icon-theme
Depends: libc6 (>= 2.4)
Depends: libmagickcore-6.q16-6 (>= 8:6.9.10.2)
Depends: libmagickwand-6.q16-6 (>= 8:6.9.10.2)
hicolor-icon-theme
libc6
Depends: libcrypt1 (>= 1:4.4.10-10ubuntu4)
Depends: libgcc-s1
libcrypt1
Depends: libc6 (>= 2.25)
```
The apt-rdepends tool is quite versatile. It can also calculate the reverse dependencies. Which means, you can see what other packages depend on a certain package.
```
apt-rdepends -r package_name
```
The output could be pretty big because it will print the reverse dependency tree.
```
[email protected]:~$ apt-rdepends -r ffmpeg
Reading package lists... Done
Building dependency tree
Reading state information... Done
ffmpeg
Reverse Depends: ardour-video-timeline (>= 1:5.12.0-3ubuntu4)
Reverse Depends: deepin-screen-recorder (5.0.0-1build2)
Reverse Depends: devede (4.15.0-2)
Reverse Depends: dvd-slideshow (0.8.6.1-1)
Reverse Depends: green-recorder (>= 3.2.3)
```
I hope this quick tutorial was helpful in improving your command line knowledge a bit. Stay tuned for more such tips.
--------------------------------------------------------------------------------
via: https://itsfoss.com/check-dependencies-package-ubuntu/
作者：[Abhishek Prakash][a]
选题：[lujun9972][b]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://itsfoss.com/author/abhishek/
[b]: https://github.com/lujun9972
[1]: https://wiki.debian.org/Apt
[2]: https://itsfoss.com/handbrake/
[3]: https://ffmpeg.org/
[4]: https://gstreamer.freedesktop.org/
[5]: https://itsfoss.com/install-handbrake-ubuntu/
[6]: https://itsfoss.com/apt-search-command/
[7]: https://itsfoss.com/install-media-codecs-ubuntu/
[8]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/08/apt-check-dependencies-ubuntu.png?resize=800%2C297&ssl=1
[9]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/08/check-dpendencies-of-deb-package.png?resize=800%2C432&ssl=1

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translated/tech/20200827 How to Check Dependencies of a Package in Ubuntu-Debian-based Linux Distributions.md Normal file
View File

@ -0,0 +1,189 @@
[#]: collector: (lujun9972)
[#]: translator: (FSSlc)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (How to Check Dependencies of a Package in Ubuntu/Debian-based Linux Distributions)
[#]: via: (https://itsfoss.com/check-dependencies-package-ubuntu/)
[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/)
如何在基于 Ubuntu 或 Debian 的 Linux 发行版中查看一个软件包的依赖
======
在 Ubuntu 或 Debian 中通过命令行来安装应用是一件很简单的事，你只需要执行 `apt install package_name` 就可以了。
但如果你想在安装一个软件包之前或之后知晓这个软件包的依赖，那该怎么办呢？
在本教程中，我将向你展示多种方法来在 Ubuntu 或其他使用 [APT 包管理器][1] 的 Debian 系 Linux 发行版中查看一个软件包的依赖。
### 在 Ubuntu 中什么是包依赖？
当你在 Linux 中安装一个软件包，有时这个软件包还需要其他的软件包来使它工作正常。这些额外的软件包就叫作这个包的依赖。假如这些软件包之前没有在系统中被安装，那么这些依赖在安装这个软件包的同时会被自动安装上。
举个例子，用来转换视频格式的 GUI 工具 [HandBrake][2] 需要 [FFmpeg][3]、[GStreamer][4] 软件包。所以对于 HandBrake 来说， FFmpeg 和 GStreamer 就是它的包依赖。
假如在你的系统上这些软件包没有被安装，则当你 [在 Ubuntu 上安装 HandBrake][5] 时，就会自动安装上它们。
### 在 Ubuntu 和基于 Debian 的发行版中查看一个软件包的依赖
正如在 Linux 上经常发生的那样，有多种方法来达到相同的目标。下面让我们一起瞧瞧查看一个软件包依赖的多种方法。
#### 使用 apt show 来查看依赖
你可以使用 [apt show 命令][6] 来展示一个包的详细信息。其中依赖信息就是其中一部分，你可以在以 Depends 打头的那些行中看到它们。
例如，下面展示的是使用 `apt show` 展示 [ubuntu-restricted-extras][7] 这个包的详细信息：
```
[email protected]:~$ apt show ubuntu-restricted-extras
Package: ubuntu-restricted-extras
Version: 67
Priority: optional
Section: multiverse/metapackages
Origin: Ubuntu
Maintainer: Ubuntu Developers <[email protected]>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 14.3 kB
Depends: ubuntu-restricted-addons
Recommends: libavcodec-extra, ttf-mscorefonts-installer, unrar
Download-Size: 3,200 B
APT-Manual-Installed: yes
APT-Sources: http://us.archive.ubuntu.com/ubuntu focal/multiverse amd64 Packages
Description: Commonly used media codecs and fonts for Ubuntu
This collection of packages includes:
- MP3 and other audio codec software to play various audio formats
(GStreamer plugins)
- software to install the Microsoft Web fonts
- the Adobe Flash plugin
- LAME, software to create compressed audio files.
.
This software does not include libdvdcss2, and will not let you play
encrypted DVDs. For more information, see
https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs
.
These software packages are from the Multiverse channel, restricted by
copyright or legal issues in some countries. For more information, see
http://www.ubuntu.com/ubuntu/licensing
```
如你所见，`ubuntu-restricted-extras` 包依赖于 `ubuntu-restricted-addons` 这个软件包。
但你得小心的是依赖包还可能依赖于其他包，这样一直循环往复直到尽头。但幸好 APT 包管理器可以为你处理这些复杂的依赖关系，自动地安装所有的依赖（大多数情况下）。
> **什么是推荐包？**
>
> 你注意到了上面结果输出中以 Recommends 开头的那些行了吗？
>
> 推荐包不是软件包的直接依赖，但它们可以开启软件包的一些额外功能。
>
> 正如你上面看到的那样， `ubuntu-restricted-extras` 包有着 `ttf-mscorefonts-installer` 这个推荐包，用来在 Ubuntu 上安装 Microsoft 的字体。
>
> 这些推荐包也会默认被一同安装上，假如你想显式地禁止这些推荐包的安装，你可以像下面这样使用 `–-no-install-recommends` 选项。
>
> `sudo apt install --no-install-recommends package_name`
#### 使用 apt-cache 来直接获取依赖信息
上面通过 `apt show` 的方式会获取到大量信息，假如你想在脚本中获取到依赖信息，那么 `apt-cache` 命令将会给你一个更好且更简洁的输出结果。
```
apt-cache depends package_name
```
下面的输出看起来更加干净，不是吗？
![][8]
#### 使用 dpkg 来查看一个 DEB 文件的依赖
`apt` 和 `apt-cache` 都作用于一个软件仓库中的软件包，但假如你下载了一个 DEB 文件，那么这两个命令就不起作用了。
在这种情形下，你可以使用 `dpkg` 命令的 `-I` 或 `--info` 选项。
```
dpkg -I path_to_deb_file
```
依赖信息就可以在以 Depends 开头的那些行中找到。
![][9]
#### 使用 apt-rdepends 来查看依赖及依赖的依赖
假如你想查看更多关于依赖的信息，那么你可以使用 `apt-rdepends` 工具。这个工具可以创建完整的依赖树。这样你就可以得到一个软件包的依赖以及这些依赖的依赖。
它不是一个常规的 apt 命令，所以你需要从 universe 软件仓库中安装上它：
```
sudo apt install apt-rdepends
```
这个命令的输出通常很多，取决于依赖树的大小。
```
Reading package lists... Done
Building dependency tree
Reading state information... Done
shutter
Depends: procps
Depends: xdg-utils
imagemagick
Depends: imagemagick-6.q16 (>= 8:6.9.2.10+dfsg-2~)
imagemagick-6.q16
Depends: hicolor-icon-theme
Depends: libc6 (>= 2.4)
Depends: libmagickcore-6.q16-6 (>= 8:6.9.10.2)
Depends: libmagickwand-6.q16-6 (>= 8:6.9.10.2)
hicolor-icon-theme
libc6
Depends: libcrypt1 (>= 1:4.4.10-10ubuntu4)
Depends: libgcc-s1
libcrypt1
Depends: libc6 (>= 2.25)
```
`apt-rdepends` 工具的功能非常多样，它还可以用来计算反向依赖。这意味着你可以查看某个特定的包被哪些软件包依赖。
```
apt-rdepends -r package_name
```
输出可能会非常多，因为它将打印出反向依赖树。
```
[email protected]:~$ apt-rdepends -r ffmpeg
Reading package lists... Done
Building dependency tree
Reading state information... Done
ffmpeg
Reverse Depends: ardour-video-timeline (>= 1:5.12.0-3ubuntu4)
Reverse Depends: deepin-screen-recorder (5.0.0-1build2)
Reverse Depends: devede (4.15.0-2)
Reverse Depends: dvd-slideshow (0.8.6.1-1)
Reverse Depends: green-recorder (>= 3.2.3)
```
我希望这个快速的教程可以帮助你提高一点儿你的命令行知识。为了知晓更多类似小知识点，请保持关注。
--------------------------------------------------------------------------------
via: https://itsfoss.com/check-dependencies-package-ubuntu/
作者：[Abhishek Prakash][a]
选题：[lujun9972][b]
译者：[FSSlc](https://github.com/FSSlc)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://itsfoss.com/author/abhishek/
[b]: https://github.com/lujun9972
[1]: https://wiki.debian.org/Apt
[2]: https://itsfoss.com/handbrake/
[3]: https://ffmpeg.org/
[4]: https://gstreamer.freedesktop.org/
[5]: https://itsfoss.com/install-handbrake-ubuntu/
[6]: https://itsfoss.com/apt-search-command/
[7]: https://itsfoss.com/install-media-codecs-ubuntu/
[8]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/08/apt-check-dependencies-ubuntu.png?resize=800%2C297&ssl=1
[9]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/08/check-dpendencies-of-deb-package.png?resize=800%2C432&ssl=1