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[#]: collector: (lujun9972)
[#]: translator: (jlztan)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (What is PPA? Everything You Need to Know About PPA in Linux)
[#]: via: (https://itsfoss.com/ppa-guide/)
[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/)
What is PPA? Everything You Need to Know About PPA in Linux
======
**Brief: An in-depth article that covers almost all the questions around using PPA in Ubuntu and other Linux distributions.**
If you have been using Ubuntu or some other Linux distribution based on Ubuntu such as Linux Mint, Linux Lite, Zorin OS etc, you may have come across three magical lines of this sort:
```
sudo add-apt-repository ppa:dr-akulavich/lighttable
sudo apt-get update
sudo apt-get install lighttable-installer
```
A number of websites suggest these kind of lines to [install applications in Ubuntu][1]. This is what is called installing an application using PPA.
But what is PPA? Why is it used? Is it safe to use PPA? How to properly use PPA? How to delete a PPA?
I’ll answer all of the above questions in this detailed guide. Even if you already know a few things about PPAs, I am sure this article will still add to your knowledge.
Do note that I am writing this article using Ubuntu. Therefore I’ll use the term Ubuntu almost everywhere but the explanations and steps are also applicable to other Debian/Ubuntu based distributions.
### What is PPA? Why is it used?
![Everything you need to know about PPA in Ubuntu Linux][2]
PPA stands for Personal Package Archive.
Does that make sense? Probably not.
Before you understand PPA, you should know the concept of repositories in Linux. I won’t go into details here though.
#### Concept of repositories and package management
A repository is a collection of files that has information about various software, their versions and some other details like the checksum. Each Ubuntu version has its own official set of four repositories:
* **Main** – Canonical-supported free and open-source software.
* **Universe** – Community-maintained free and open-source software.
* **Restricted** – Proprietary drivers for devices.
* **Multiverse** – Software restricted by copyright or legal issues.
You can see such repositories for all Ubuntu versions [here][3]. You can browse through them and also go to the individual repositories. For example, Ubuntu 16.04 main repository can be found [here][4].
So basically it’s a web URL that has information about the software. How does your system know where are these repositories?
This information is stored in the sources.list file in the directory /etc/apt. If you look at its content, you’ll see that it has the URL of the repositories. The lines with # at the beginning are ignored.
Now when you run the command sudo apt update, your system uses [APT tool][5] to check against the repo and stores the information about the software and their version in a cache. When you use the command sudo apt install package_name, it uses the information to get that package from the URL where the actual software is stored.
If the repository doesn’t have the information about a certain package, you’ll see an error like:
```
E: Unable to locate package
```
At this point, I recommend reading my [guide to using apt commands][6]. This will give you a much better understanding of apt commands, update etc.
So this was about repositories. But what is PPA? How does it enter into the picture?
#### Why is PPA used?
As you can see, Ubuntu controls what software and more importantly which version of a software you get on your system. But imagine if a software developer releases a new version of the software.
Ubuntu won’t make it available immediately. There is a procedure to check if the new version of the software is compatible with the system or not. This ensures the stability of the system.
But this also means that it will be some weeks or in some cases, some months before it is made available by Ubuntu. Not everyone would want to wait that long to get their hands on the new version of their favorite software.
Similarly, suppose someone develops a software and wants Ubuntu to include that software in the official repositories. It again will take months before Ubuntu makes a decision and includes it in the official repositories.
Another case would be during beta testing. Even if a stable version of the software is available in the official repositories, a software developer may want some end users to test their upcoming release. How do they enable the end user to beta test the upcoming release?
Enter PPA!
### How to use PPA? How does PPA work?
[PPA][7], as I already told you, means Personal Package Archive. Mind the word ‘Personal’ here. That gives the hint that this is something exclusive to a developer and is not officially endorsed by the distribution.
Ubuntu provides a platform called Launchpad that enables software developers to create their own repositories. An end user i.e. you can add the PPA repository to your sources.list and when you update your system, your system would know about the availability of this new software and you can install it using the standard sudo apt install command like this.
`sudo add-apt-repository ppa:dr-akulavich/lighttable`
`sudo apt-get update`
`sudo apt-get install lighttable-installer`
To summarize:
* sudo add-apt-repository <PPA_info> <– This command adds the PPA repository to the list.
* sudo apt-get update <– This command updates the list of the packages that can be installed on the system.
* sudo apt-get install <package_in_PPA> <– This command installs the package.
You see that it is important to use the command sudo apt update or else your system will not know when a new package is available.
Now let’s take a look at the first command in a bit more detail.
```
sudo add-apt-repository ppa:dr-akulavich/lighttable
```
You would notice that this command doesn’t have a URL to the repository. This is because the tool has been designed to abstract the information about URL from you.
Just a small note. If you add ppa:dr-akulavich/lighttable, you get Light Table. But if you add ppa:dr-akulavich, you’ll get all the repository or packages mentioned in the ‘upper repository’. It’s hierarchical.
Basically, when you add a PPA using add-apt-repository, it will do the same action as if you manually run these commands:
```
deb http://ppa.launchpad.net/dr-akulavich/lighttable/ubuntu YOUR_UBUNTU_VERSION_HERE main
deb-src http://ppa.launchpad.net/dr-akulavich/lighttable/ubuntu YOUR_UBUNTU_VERSION_HERE main
```
The above two lines are the traditional way to add any repositories to your sources.list. But PPA does it automatically for you, without wondering about the exact repository URL and operating system version.
One important thing to not here is that when you use PPA, it doesn’t change your original sources.list. Instead, it creates two files in /etc/apt/sources.d directory, a list and a back up file with suffix ‘save’.
![Using a PPA in Ubuntu][8]PPA create separate sources.list
The files with suffix ‘list’ has the command that adds the information about the repository.
![PPA add repository information][9]Content of source.list of a PPA
This is a safety measure to ensure that adding PPAs don’t mess with the original sources.list. It also helps in removing the PPA.
#### Why PPA? Why not DEB packages?
You may ask why should you use PPA when it involves using command line which might not be preferred by everyone. Why not just distribute a DEB package that can be installed graphically?
The answer lies in the update procedure. If you install a software using a DEB package, there is no guarantee that the installed software will be updated to a newer version when you run sudo apt update && sudo apt upgrade.
It’s because the apt upgrade procedure relies on the sources.list. If there is no entry for a software, it doesn’t get the update via the standard software updater.
So does it mean software installed using DEB never gets an update? No, not really. It depends on how the package was created.
Some developers automatically add an entry to the sources.list and then it is updated like a regular software. Google Chrome is one such example.
Some software would notify you of availability of a new version when you try to run it. You’ll have to download the new DEB package and run it again to update the current software to a newer version. Oracle Virtual Box is an example in this case.
For the rest of the DEB packages, you’ll have to manually look for an update and this is not convenient, especially if your software is meant for beta testers. You need to add more updates frequently. This is where PPA come to the rescue.
#### Offical PPA vs unofficial PPA
You may also hear the term official PPA or unofficial PPA. What’s the difference?
When developers create PPA for their software, it is called the official PPA. Quite obviously because it is coming from none other than the project developers.
But at times, individuals create PPA of projects that were created by other developers.
Why would someone do that? Because many developers just provide the source code of the software and you know that [installing software from source code in Linux][10] is a pain and not everyone could or would do that.
This is why volunteers take it upon themselves to create a PPA from those source code so that other users can install the software easily. After all, using those 3 lines is a lot easier than battling the source code installation.
#### Make sure that a PPA is available for your distribution version
When it comes to using PPA in Ubuntu or any other Debian based distribution, there are a few things you should keep in mind.
Not every PPA is available for your particular version. You should know [which Ubuntu version][11] you are using. The codename of the release is important because when you go to the webpage of a certain PPA, you can see which Ubuntu versions are supported by the PPA.
For other Ubuntu-based distributions, you can check the content of /etc/os-release to [find out the Ubuntu version][11] information.
![Verify PPA availability for Ubuntu version][12]Check if PPA is available for your Ubuntu version
How to know the PPA url? Simply search on the internet with the PPA name like ppa:dr-akulavich/lighttable and you’ll get the first result from [Launchpad][13], the official platform for hosting PPA. You can also go to Launchpad and search for the required PPA directly there.
If you don’t verify and add the PPA, you may see an error like this when you try to install a software not available for your version.
```
E: Unable to locate package
```
What’s worse is that since it has been added to your source.list, each time you run software updater, you’ll see an error “[Failed to download repository information][14]“.
![Failed to download repository information Ubuntu 13.04][15]
If you run sudo apt update in the terminal, the error will have more details about which repository is causing the trouble. You can see something like this in the end of the output of sudo apt update:
```
W: Failed to fetch http://ppa.launchpad.net/venerix/pkg/ubuntu/dists/raring/main/binary-i386/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
```
Which is self-explanatory because the system cannot find the repository for your version. Remember what we saw earlier about repository structure? APT will try to look for software information in the place <http://ppa.launchpad.net/\><PPA_NAME>/ubuntu/dists/Ubuntu_Version
And if the PPA for the specific version is not available, it will never be able to open the URL and you get the famous 404 error.
#### Why are PPAs not available for all the Ubuntu release versions?
It is because someone has to compile the software and create a PPA out of it on the specific versions. Considering that a new Ubuntu version is released every six months, it’s a tiresome task to update the PPA for every Ubuntu release. Not all developers have time to do that.
#### How to install the application if PPA is not available for your version?
It is possible that though the PPA is not available for your Ubuntu version, you could still download the DEB file and install the application
Let’s say that you go to the Light Table PPA. Using the knowledge about PPA you just learned, you realize that the PPA is not available for your specific Ubuntu release.
What you can do is to click on the ‘View package details’.
![Get DEB file from PPA][16]
And in here, you can click on a package to reveal more details. You’ll also find the source code and the DEB file of the package here.
![Download DEB file from PPA][17]
I advise [using Gdebi to install these DEB files][18] instead of the Software Center because Gdebi is a lot better at handling dependencies.
Do note that the package installed this way might not get any future updates.
I think you have read enough about adding PPAs. How about removing a PPA and the software installed by it?
### How to delete PPA?
I have written about [deleting PPA][19] in the past. I am going to describe the same methods here as well.
I advise deleting the software that you installed from a PPA before removing the PPA. If you just remove the PPA, the installed software remains in the system but it won’t get any updates. You wouldn’t want that, would you?
So, the question comes, how to know which application was installed by which PPA?
#### Find packages installed by a PPA and remove them
Ubuntu Software Center doesn’t help here. You’ll have to use Synaptic package manager here which has more advanced features.
You can install Synaptic from Software Center or use the command below:
```
sudo apt install synaptic
```
Once installed, start Synaptic package manager and select Origin. You’ll see various repositories added to the system. PPA entries will be labeled with prefix PPA. Click on them to see the packages that are available by the PPA. Installed software will have appropriate symbol before it.
![Managing PPA with Synaptic package manager][20]Find packages installed via a PPA
Once you have found the packages, you can delete them from Synaptic itself. Otherwise, you always have the option to use the command line:
```
sudo apt remove package_name
```
Once you have removed the packages installed by a PPA, you can continue to remove the PPA from your sources.list.
#### Remove a PPA graphically
Go to Software & Updates and then go to tab Other Software. Look for the PPA that you want to remove:
![Delete a PPA from Software Source][21]
You have two options here. Either you deselect the PPA or you choose the Remove option.
The difference is that when you deselect a PPA entry, your system will comment out the repository entry in its ppa_name.list file in /etc/apt/sources.list.d but if you choose the Remove option, it will delete the repository entry from its ppa_name.list file in /etc/apt/sources.list.d directory.
In both the cases, the files ppa_name.list remains in the said directory, even if it is empty.
### Is it safe to use PPA?
It is a subjective question. Purists abhor PPA because most of the time PPAs are from third-party developers. But at the same time, PPAs are popular in the Debian/Ubuntu world as they provide an easier installation option.
As far as the security is concerned, it’s less likely that you use a PPA and your Linux system is hacked or injected with malware. I don’t recall such an incident ever happened so far.
Official PPAs can be used without thinking twice. Using unofficial PPA is entirely your decision.
As a rule of thumb, you should avoid installing a program via a third party PPA if it the program requires sudo access to run.
### What do you think about using PPA?
I know it’s a long read but I wanted to give you a better understanding of PPA. I hope this detailed guide answered most of your questions about using PPA.
If you have more questions about PPA, please feel free to ask in the comment section.
If you notice any technical or grammatical error or if you have suggestions for improving this article, please let me know.
--------------------------------------------------------------------------------
via: https://itsfoss.com/ppa-guide/
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://itsfoss.com/remove-install-software-ubuntu/
[2]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/12/what-is-ppa.png?resize=800%2C450&ssl=1
[3]: http://archive.ubuntu.com/ubuntu/dists/
[4]: http://archive.ubuntu.com/ubuntu/dists/xenial/main/
[5]: https://wiki.debian.org/Apt
[6]: https://itsfoss.com/apt-command-guide/
[7]: https://launchpad.net/ubuntu/+ppas
[8]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/01/ppa-sources-list-files.png?resize=800%2C259&ssl=1
[9]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/01/content-of-ppa-list.png?ssl=1
[10]: https://itsfoss.com/install-software-from-source-code/
[11]: https://itsfoss.com/how-to-know-ubuntu-unity-version/
[12]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2017/12/verify-ppa-availibility-version.jpg?resize=800%2C481&ssl=1
[13]: https://launchpad.net/
[14]: https://itsfoss.com/failed-to-download-repository-information-ubuntu-13-04/
[15]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2013/04/Failed-to-download-repository-information-Ubuntu-13.04.png?ssl=1
[16]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/12/deb-from-ppa.jpg?resize=800%2C483&ssl=1
[17]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/12/deb-from-ppa-2.jpg?resize=800%2C477&ssl=1
[18]: https://itsfoss.com/gdebi-default-ubuntu-software-center/
[19]: https://itsfoss.com/how-to-remove-or-delete-ppas-quick-tip/
[20]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/01/ppa-synaptic-manager.jpeg?resize=800%2C394&ssl=1
[21]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2012/08/Delete-a-PPA.jpeg?ssl=1

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[#]: collector: "lujun9972"
[#]: translator: "jlztan"
[#]: reviewer: " "
[#]: publisher: " "
[#]: url: " "
[#]: subject: "What is PPA? Everything You Need to Know About PPA in Linux"
[#]: via: "https://itsfoss.com/ppa-guide/"
[#]: author: "Abhishek Prakash https://itsfoss.com/author/abhishek/"
# 什么是 PPA？你需要知道的关于 Linux 中 PPA 的一切
**简介：一篇涵盖了在 Ubuntu 和其他 Linux 发行版中使用 PPA 的几乎所有问题的深入的文章。**
如果你一直在使用 Ubuntu 或基于 Ubuntu 的其他 Linux 发行版，例如 Linux Mint、Linux Lite、Zorin OS 等，你可能会遇到以下三行神奇的命令：
```
sudo add-apt-repository ppa:dr-akulavich/lighttable
sudo apt-get update
sudo apt-get install lighttable-installer
```
许多网站推荐使用类似于以上几行的形式 [在 Ubuntu 中安装应用程序][1]。这就是所谓的使用 PPA 安装应用程序。
但什么是 PPA？为什么用它？使用 PPA 安全吗？如何正确使用 PPA？如何删除 PPA？
我将在这个详细的指南中回答上述所有问题。即使你已经了解了一些关于 PPA 的事情，我相信这篇文章仍然会让你了解这方面的更多知识。
请注意我正在使用 Ubuntu 撰写本文。因此，我几乎可以在任何地方使用 Ubuntu 这个术语，但文中的说明和步骤也适用于其他基于 Debian/Ubuntu 的发行版。
### 什么是 PPA？为什么要使用 PPA？
![Everything you need to know about PPA in Ubuntu Linux][2]
PPA 表示 个人软件包存档Personal Package Archive<ruby>个人软件包存档<rt>Personal Package Archive</rt></ruby>。
这样说容易理解吗？可能不是很容易。
在了解 PPA 之前，你应该了解 Linux 中软件仓库的概念。关于软件仓库，在这里我不会详述。
#### 软件仓库和包管理的概念
软件仓库是一组文件，其中包含各种软件及其版本的信息，以及校验和等其他一些详细信息。每个版本的 Ubuntu 都有自己的四个官方软件仓库：
- Main - Canonical 支持的免费和开源软件。
- Universe - 社区维护的免费和开源软件。
- Restricted - 设备的专有驱动程序。
- Multiverse - 受版权或法律问题限制的软件。
你可以在 [这里][3] 看到所有版本的 Ubuntu 的软件仓库。你可以浏览并转到各个仓库。例如，可以在 [这里][4] 找到 Ubuntu 16.04 的主存储库。
所以，PPA 基本上是一个包含软件信息的网址。那你的系统又是如何知道这些仓库的位置的呢？
这些信息存储在 `/etc/apt` 目录中的 `sources.list` 文件中。如果查看此文件的内容，你就会看到里面有软件仓库的网址。`#` 开头的行将被忽略。
这样的话，当你运行 `sudo apt update` 命令时，你的系统将使用 [APT 工具][5] 来检查软件仓库并将软件及其版本信息存储在缓存中。当你使用 `sudo apt install package_name` 命令时，它通过该信息从实际存储软件的网址获取该软件包。
如果软件仓库中没有关于某个包的信息，你将看到如下错误：
```
E: Unable to locate package
```
此时，建议阅读我的 [apt 命令使用指南][6] 一文，这将帮你更好地理解 `apt`、`update` 等命令。
以上是关于软件仓库的内容。但什么是 PPA？PPA 和软件仓库又有什么关联呢？
#### 为什么要用 PPA？
如你所见，Ubuntu 对系统中的软件进行管理，更重要的是控制你在系统上获得哪个版本的软件。但想象一下开发人员发布了软件的新版本的情况。
Ubuntu 不会立即提供该新版本的软件。需要一个步骤来检查此新版本的软件是否与系统兼容，从而可以确保系统的稳定性。
但这也意味着它需要经过几周才能在 Ubuntu 上可用，在某些情况下，这可能需要几个月的时间。不是每个人都想等待那么长时间才能获得他们最喜欢的软件的新版本。
类似地，假设有人开发了一款软件，并希望 Ubuntu 将该软件包含在官方软件仓库中。在 Ubuntu 做出决定并将其包含在官方存软件仓库之前，还需要几个月的时间。
另一种情况是在 beta 测试阶段。即使官方软件仓库中提供了稳定版本的软件，软件开发人员也可能希望某些终端用户测试他们即将发布的版本。他们是如何使终端用户对即将发布的版本进行 beta 测试的呢？
通过 PPA！
### 如何使用 PPA？PPA 是怎样工作的？
正如我已经告诉过你的那样，[PPA][7] 代表个人软件包存档Personal Package Archive<ruby>个人软件包存档<rt>Personal Package Archive</rt></ruby>。在这里注意 “个人” 这个词，它暗示了这是开发人员独有的东西，并没有得到分发的正式许可。
Ubuntu 提供了一个名为 Launchpad 的平台，使软件开发人员能够创建自己的软件仓库。 终端用户，也就是你，可以将 PPA 仓库添加到 `sources.list` 文件中，当你更新系统时，你的系统会知道这个新软件的可用性，然后你可以使用标准的 `sudo apt install` 命令安装它。
`sudo add-apt-repository ppa:dr-akulavich/lighttable`
`sudo apt-get update`
`sudo apt-get install lighttable-installer`
概括一下上面三个命令：
- `sudo add-apt-repository <PPA_info>` < - 此命令将 PPA 仓库添加到列表中。
- `sudo apt-get update` < - 此命令更新可以在当前系统上安装的软件包列表。
- `sudo apt-get install <package_in_PPA>` < - 此命令安装软件包。
你会发现使用 `sudo apt update` 命令非常重要，否则你的系统将无法知道新软件包何时可用。
现在让我们更详细地看一下第一个命令。
```
sudo add-apt-repository ppa:dr-akulavich/lighttable
```
你会注意到此命令没有软件仓库的 URL。这是因为该工具被设计成将 URL 信息抽象之后再展示给你。
小小注意一下：如果你添加的是 `ppa:dr-akulavich/lighttable`，你会得到 Light Table。但是如果你添加 `ppa:dr-akulavich`，你将得到 “上层软件仓库” 中的所有仓库或软件包。它是按层级划分的。
基本上，当您使用 `add-apt-repository` 添加 PPA 时，它将执行与手动运行这些命令相同的操作：
```
deb http://ppa.launchpad.net/dr-akulavich/lighttable/ubuntu YOUR_UBUNTU_VERSION_HERE main
deb-src http://ppa.launchpad.net/dr-akulavich/lighttable/ubuntu YOUR_UBUNTU_VERSION_HERE main
```
以上两行是将任何软件仓库添加到你系统的 `sources.list` 文件的传统方法。但 PPA 会自动为你完成这些工作，无需考虑确切的软件仓库 URL 和操作系统版本。
此处不那么重要的一点是，当你使用 PPA 时，它不会更改原始的 `sources.list` 文件。相反，它在 `/etc/apt/sources.d` 目录中创建了两个文件，一个 “list” 文件和一个带有 “save” 后缀的备份文件。
![Using a PPA in Ubuntu][8]
PPA 创建了单独的 `sources.list` 文件
带有后缀 “list” 的文件含有添加软件仓库的信息的命令。
![PPA add repository information][9]
一个 PPA 的 `source.list` 文件的内容
这是一种安全措施，可以确保添加的 PPA 不会和原始的 `sources.list` 文件弄混，它还有助于移除 PPA。
#### 为什么使用 PPA？为何不用 DEB 包
你可能会问为什么要使用 PPA，PPA 需要通过命令行使用，而不是每个人都喜欢用命令行。为什么不直接分发可以图形方式安装的 DEB 包呢？
答案在于更新的过程。如果使用 DEB 包安装软件，将无法保证在运行 `sudo apt update` 和 `sudo apt upgrade` 命令时，已安装的软件会被更新为较新的版本。
这是因为 apt 的升级过程依赖于 `sources.list` 文件。如果文件中没有相应的软件条目，则不会通过标准软件更新程序获得更新。
那么这是否意味着使用 DEB 安装的软件永远不会得到更新？不是的。这取决于 DEB 包的创建方式。
一些开发人员会自动在 `sources.list ` 中添加一个条目，这样软件就可以像普通软件一样更新。谷歌 Chrome 浏览器就是这样一个例子。
某些软件会在运行时通知你有新版本可用。你必须下载新的 DEB 包并再次运行，来将当前软件更新为较新版本。Oracle Virtual Box 就是这样一个例子。
对于其余的 DEB 软件包，你必须手动查找更新，这很不方便，尤其是在你的软件面向 Beta 测试者时，你需要频繁的添加很多更新。这正是 PPA 要解决的问题。
#### 官方 PPA vs 非官方 PPA
你或许听过官方 PPA 或非官方 PPA 这个词，二者有什么不同呢？
开发人员为他们的软件创建的 PPA 称为官方 PPA。很明显，这是因为它来自项目开发者。
但有时，个人会创建由其他开发人员所创建的项目的 PPA。
为什么会有人这样做？ 因为许多开发人员只提供软件的源代码，而且你也知道 [在 Linux 中从源代码安装软件][10] 是一件痛苦的事情，并不是每个人都可以或者会这样做。
这就是志愿者自己从这些源代码创建 PPA 以便其他用户可以轻松安装软件的原因。毕竟，使用这 3 行命令比从源代码安装要容易得多。
#### 确保你的 Linux 发行版本可以使用 PPA
当在 Ubuntu 或任何其他基于 Debian 的发行版中使用 PPA 时，你应该记住一些事情。
并非每个 PPA 都适用于你的特定版本。你应该知道正在使用 [哪个版本的 Ubuntu][11]。版本的开发代号很重要，因为当你访问某个 PPA 的页面时，你可以看到该 PPA 都支持哪些版本的 Ubuntu。
对于其他基于 Ubuntu 的发行版，你可以查看 `/etc/os-release` 的内容来 [找出 Ubuntu 版本][11] 的信息。
![Verify PPA availability for Ubuntu version][12]
检查 PPA 是否适用于你的 Ubuntu 版本
如何知道 PPA 的网址呢？只需在网上搜索 PPA 的名称，如 `ppa:dr-akulavich/lighttable`，第一个搜索结果来自 [Launchpad][13]，这是托管 PPA 的官方平台。你也可以转到 Launchpad 并直接在那里搜索所需的 PPA。
如果不验证是否适用当前的版本就添加 PPA，当尝试安装不适用于你的系统版本的软件时，可能会看到类似下面的错误。
```
E: Unable to locate package
```
更糟糕的是，因为它已经添加到你的 `source.list` 中，每次运行软件更新程序时，你都会看到 “[无法下载软件仓库信息][14]” 的错误。
![Failed to download repository information Ubuntu 13.04][15]
如果你在终端中运行 `sudo apt update`，错误提示将包含导致此问题的仓库的更多详细信息。你可以在 `sudo apt update` 的输出内容结尾看到类似的内容：
```
W: Failed to fetch http://ppa.launchpad.net/venerix/pkg/ubuntu/dists/raring/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
```
上面的错误提示说的很明白，是因为系统找不到当前版本对应的仓库。还记得我们之前看到的仓库结构吗？APT 将尝试在 <http://ppa.launchpad.net/\><PPA_NAME>/ubuntu/dists/Ubuntu_Version 中寻找软件信息。
如果特定版本的 PPA 不可用，它将永远无法打开 URL，你会看到著名的404错误。
#### 为什么 PPA 不适用于所有 Ubuntu 发行版？
这是因为 PPA 的作者必须编译软件并在特定版本上创建 PPA。考虑到每六个月发布一个新的 Ubuntu 版本，为每个版本的 Ubuntu 更新 PPA 是一项繁琐的任务，并非所有开发人员都有时间这样做。
#### 如果 PPA 不适用于你的系统版本，该如何安装应用程序？
尽管 PPA 不适用于你的 Ubuntu 版本，你仍然可以下载 DEB 文件并安装应用程序。
比如说，你访问 Light Table 的 PPA 页面，使用刚刚学到的有关 PPA 的知识，你会发现 PPA 不适用于你的特定 Ubuntu 版本。
你可以点击 `查看软件包详细信息`。
![Get DEB file from PPA][16]
在这里，你可以单击软件包以显示更多详细信息，还可以在此处找到包的源代码和 DEB 文件。
![Download DEB file from PPA][17]
我建议 [使用 Gdebi 安装这些 DEB 文件][18] 而不是通过软件中心，因为 Gdebi 在处理依赖项方面要好得多。
请注意，以这种方式安装的软件包可能无法获得任何将来的更新。
我认为你已经阅读了足够多的关于添加 PPA 的内容，那么如何删除 PPA 及其安装的软件呢？
### 如何删除 PPA？
我过去曾写过 [删除 PPA][19] 的教程，这里写的也是同样的方法。
我建议在删除 PPA 之前删除从 PPA 安装的软件。如果只是删除 PPA，则已安装的软件仍保留在系统中，但不会获得任何更新。这不是你想要的，不是吗？
那么，问题来了，如何知道是哪个 PPA 安装了哪个应用程序？
#### 查找 PPA 安装的软件包并将其移除
Ubuntu 软件中心无法移除 PPA 安装的软件包，你必须使用具有更多高级功能的 Synaptic 包管理器。
可以从软件中心安装 Synaptic 或使用以下命令进行安装：
```
sudo apt install synaptic
```
安装后，启动 Synaptic 包管理器并选择 Origin。你会看到添加到系统的各种软件仓库。 PPA 条目将以前缀 PPA 进行标识，单击以查看 PPA 可用的包。已安装的软件前面会有恰当的符号进行标识。
![Managing PPA with Synaptic package manager][20]
查找通过 PPA 安装的软件包
找到包后，你可以从 Synaptic 删除它们。此外，也始终可以选择使用命令行进行移除：
```
sudo apt remove package_name
```
删除 PPA 安装的软件包后，你可以继续从 `sources.list` 中删除PPA。
#### 以图形界面的方式删除 PPA
在设置中打开 “软件和更新”，然后点击 “其他软件” 选项卡。查找要删除的 PPA：
![Delete a PPA from Software Source][21]
此处你可以进项两项操作，可以取消选择 PPA 或选择 “删除” 选项。
区别在于，当你取消选择 PPA 条目时，系统将在 `/etc/apt/sources.list.d` 中的`ppa_name.list` 文件中注释掉仓库条目；但如果选择 “删除” 选项，将会删除 `/etc/apt/sources.list.d`目录中 `ppa_name.list` 文件里的仓库条目。
在这两种情况下，文件 `ppa_name.list` 都保留在所在的目录中，即使它是空的。
### 使用 PPA 安全吗？
这是一个主观问题。纯粹主义者厌恶 PPA，因为大多数时候 PPA 来自第三方开发者。但与此同时，PPA 在 Debian/Ubuntu 世界中很受欢迎，因为它们提供了更简单的安装选项。
就安全性而言，使用 PPA 之后，你的 Linux 系统被黑客攻击或注入恶意软件的可能性较小。到目前为止，我不记得发生过这样的事件。
官方 PPA 可以不加考虑的使用，使用非官方 PPA 完全是你自己的决定。
根据经验，如果程序需要 sudo 权限，则应避免通过第三方 PPA 进行安装。
### 你如何看待使用 PPA？
我知道这篇文章需要挺长时间来阅读，但我想让你更好地了解 PPA。我希望这份详细指南能够回答你关于使用 PPA 的大部分问题。
如果你对 PPA 有更多疑问，请随时在评论区提问。
如果你发现任何技术或语法错误，或者有改进的建议，请告诉我。
------
via: https://itsfoss.com/ppa-guide/
作者：[Abhishek Prakash][a]
选题：[lujun9972][b]
译者：[jlztan](https://github.com/jlztan)
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://itsfoss.com/remove-install-software-ubuntu/
[2]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/12/what-is-ppa.png?resize=800%2C450&ssl=1
[3]: http://archive.ubuntu.com/ubuntu/dists/
[4]: http://archive.ubuntu.com/ubuntu/dists/xenial/main/
[5]: https://wiki.debian.org/Apt
[6]: https://itsfoss.com/apt-command-guide/
[7]: https://launchpad.net/ubuntu/+ppas
[8]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/01/ppa-sources-list-files.png?resize=800%2C259&ssl=1
[9]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/01/content-of-ppa-list.png?ssl=1
[10]: https://itsfoss.com/install-software-from-source-code/
[11]: https://itsfoss.com/how-to-know-ubuntu-unity-version/
[12]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2017/12/verify-ppa-availibility-version.jpg?resize=800%2C481&ssl=1
[13]: https://launchpad.net/
[14]: https://itsfoss.com/failed-to-download-repository-information-ubuntu-13-04/
[15]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2013/04/Failed-to-download-repository-information-Ubuntu-13.04.png?ssl=1
[16]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/12/deb-from-ppa.jpg?resize=800%2C483&ssl=1
[17]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/12/deb-from-ppa-2.jpg?resize=800%2C477&ssl=1
[18]: https://itsfoss.com/gdebi-default-ubuntu-software-center/
[19]: https://itsfoss.com/how-to-remove-or-delete-ppas-quick-tip/
[20]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/01/ppa-synaptic-manager.jpeg?resize=800%2C394&ssl=1
[21]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2012/08/Delete-a-PPA.jpeg?ssl=1