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sources/tech/20220620 How I use the attr command with my Linux filesystem.md
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How I use the attr command with my Linux filesystem
我是怎样在 Linux 文件系统中使用 attr 的
======
I use the open source XFS filesystem because of the subtle convenience of extended attributes. Extended attributes are a unique way to add context to my data.
我使用开源的 XFS 文件系统为了其扩展属性的不易察觉的便捷性。扩展属性是一种增加我数据上下文环境的独特方式。
![为什么操作系统在2017年更加重要了][1]
![Why the operating system matters even more in 2017][1]
图片来自 Internet Archive Book Images，由 Opensource.com 修改。CC BY-SA 4.0
Image by: Internet Archive Book Images. Modified by Opensource.com. CC BY-SA 4.0
术语*文件系统*是一个描述你的电脑怎样跟踪所有你创建的文件的完美词语。你的电脑存储有大量的数据，不管是文档、配置文件还是数以千计的照片。这需要一种对人和机器都好的方式。诸如 Ext4, XFS, JFS, BtrFS 的文件系统是你的电脑跟踪文件的“语言”。
The term *filesystem* is a fancy word to describe how your computer keeps track of all the files you create. Whether it's an office document, a configuration file, or thousands of digital photos, your computer has to store a lot of data in a way that's useful for both you and it. Filesystems like Ext4, XFS, JFS, BtrFS, and so on are the "languages" your computer uses to keep track of data.
你的桌面或终端可以帮助你快速找到文件。例如，你的文件管理器可能有过滤功能让你快速在家目录内浏览图片，它也可能带有搜索功能以让你使用文件名定位文件。这些特性被称作*文件属性*，正如其名，由文件头或者文件系统代码定义的文件对象的属性。大多数的文件系统记录标准的文件属性，例如文件名、文件大小、文件类型、创建时间、上次访问时间。
Your desktop or terminal can do a lot to help you find your data quickly. Your file manager might have, for instance, a filter function so you can quickly see just the image files in your home directory, or it might have a search function that can locate a file by its filename, and so on. These qualities are known as *file attributes* because they are exactly that: Attributes of the data object, defined by code in file headers and within the filesystem itself. Most filesystems record standard file attributes such as filename, file size, file type, time stamps for when it was created, and time stamps for when it was last visited.
我在电脑上使用开源的 XFS 文件系统，不是为了其的稳定性和高性能，而是为了其不易察觉的扩展属性的便捷性。
I use the open source XFS filesystem on my computers not for its reliability and high performance but for the subtle convenience of extended attributes.
### 常见的文件属性
### Common file attributes
当你保存一个文件，有关其的文件也会随同保存。常见的属性告诉操作系统是否更新访问时间，什么时间同步数据到硬盘等逻辑细节。哪些属性被保存取决于底层文件系统的功能和特性。
When you save a file, data about it are saved along with it. Common attributes tell your operating system whether to update the access time, when to synchronize the data in the file back to disk, and other logistical details. Which attributes get saved depends on the capabilities and features of the underlying filesystem.
在标准文件属性（如果有标准属性的话）之外，XFS, Ext4 和 BtrFS 文件系统都可以使用扩展文件系统。
In addition to standard file attributes (insofar as there are standard attributes), the XFS, Ext4, and BtrFS filesystems can all use extending filesystems.
### 扩展属性
### Extended attributes
XFS, Ext4 和 BtrFs 允许你创建自己任意的文件属性。由于你是自制标签，操作系统不会有内建支持，不过我像图片的 EXIF 数据一样以“标签”的方式使用。开发者们也许会选择使用扩展属性去开发应用内的自定义的功能。
XFS, Ext4, and BtrFS allow you to create your own arbitrary file attributes. Because you're making up attributes, there's nothing built into your operating system to utilize them, but I use them as "tags" for files in much the same way I use EXIF data on photos. Developers might choose to use extended attributes to develop custom capabilities in applications.
XFS 中有2种“命名空间”， **user** 和 **root** 。当创建属性时，你必须将其加入一个命名空间。你需要`sudo`或以`root`登录以将属性加入`root`命名空间。
There are two "namespaces" for attributes in XFS: **user** and **root**. When creating an attribute, you must add your attribute to one of these namespaces. To add an attribute to the **root** namespace, you must use the `sudo` command or be logged in as root.
### 增加一个属性
### Add an attribute
你可以使用`attr`和`setfattr`命令在 XFS 文件系统中为文件增加属性。
You can add an attribute to a file on an XFS filesystem with the `attr` or `setfattr` commands.
The `attr` command assumes the `user` namespace, so you only have to set (`-s` ) a name for your attribute followed by a value (`-V` ):
`attr`命令默认在`user`命名空间下进行，所以你只需要使用`-s`设置名字，`-V`在其后设置值。
```
$ attr -s flavor -V vanilla example.txt
@ -45,41 +43,36 @@ Attribute "flavor" set to a 7 byte value for example.txt:
vanilla
```
The `setfattr` command requires that you specify the target namespace:
`setfattr` 命令需要你指定目标命名空间：
```
$ setfattr --name user.flavor --value chocolate example.txt
```
### 列出扩展文件属性
### List extended file attributes
Use the `attr` or `getfattr` commands to see extended attributes you've added to a file. The `attr` command defaults to the **user** namespace and uses the `-g` option to *get* extended attributes:
使用`attr`或者`getfattr`命令去看你加到文件上的扩展属性。`attr`命令默认是**user**空间，使用`-g`以*获取*扩展属性：
```
$ attr -g flavor example.txt
Attribute "flavor" had a 9 byte value for example.txt:
chocolate
```
The `getfattr` command requires the namespace and name of the attribute:
`getfattr`命令需要用户空间和属性名字：
```
$ getfattr --name user.flavor example.txt
# file: example.txt
user.flavor="chocolate"
```
### List all extended attributes
To see all extended attributes on a file, you can use `attr -l` :
### 列出所有扩展属性
为了看一个文件的所有扩展属性，你可以使用`attr -l`：
```
$ attr -l example.txt
Attribute "md5sum" has a 32 byte value for example.txt
Attribute "flavor" has a 9 byte value for example.txt
```
Alternately, you can use `getfattr -d` :
或者，你也可以使用`getfattr -d`：
```
$ getfattr -d example.txt
@ -87,8 +80,7 @@ $ getfattr -d example.txt
user.flavor="chocolate"
user.md5sum="969181e76237567018e14fe1448dfd11"
```
Any extended file attribute can be updated with `attr` or `setfattr`, just as if you were creating the attribute:
扩展文件属性可以使用`attr`和`setfattr`更新，就像你创建这些属性一样：
```
$ setfattr --name user.flavor --value strawberry example.txt
@ -98,22 +90,20 @@ $ getfattr -d example.txt
user.flavor="strawberry"
user.md5sum="969181e76237567018e14fe1448dfd11"
```
### 其他文件系统上的属性
### Attributes on other filesystems
使用扩展属性最大的风险是忘记这些属性是对特定文件系统的。这意味着当你复制文件从一个磁盘或分区到另外一个时，这些属性都会丢失，**即使**目标位置的文件系统支持扩展属性。
The greatest risk when using extended attributes is forgetting that these attributes are specific to the filesystem they're on. That means when you copy a file from one drive or partition to another, the attributes are lost *even if the target filesystem supports extended attributes*.
To avoid losing extended attributes, you must use a tool that supports retaining them, such as the `rsync` command.
为了避免丢失扩展属性，你需要使用支持保存属性的工具，例如`rsync`命令。
```
$ rsync --archive --xattrs ~/example.txt /tmp/
```
不关你使用什么工具，如果你传输文件到一个不知道如何处理扩展属性的文件系统，这些属性都会被丢弃。
No matter what tool you use, if you transfer a file to a filesystem that doesn't know what to do with extended attributes, those attributes are dropped.
### 搜索属性
### Search for attributes
There aren't many mechanisms to interact with extended attributes, so the options for using the file attributes you've added are limited. I use extended attributes as a tagging mechanism, which allows me to associate files that have no obvious relation to one another. For instance, suppose I need a Creative Commons graphic for a project I'm working on. Assume I've had the foresight to add the extended attribute **license** to my collection of graphics. I could search my graphic folder with `find` and `getfattr` together:
没有很多与扩展属性交互的机制，所以你使用添加的文件属性的选择是有限的。我使用扩展属性作为标签机制，这让我能联系起来没有明显关系的文件。例如，假设我需要在工作中的一个项目中用知识共享的图形。假如我预见性地创建了 **license** 属性在我收集的图形中，我就可以使用`find`和`getfattr`在图形文件夹中寻找：
```
find ~/Graphics/ -type f \
@ -125,10 +115,9 @@ find ~/Graphics/ -type f \
user.license="cc-by-sa"
user.md5sum="969181e76237567018e14fe1448dfd11"
```
### 你的文件系统的秘密
### Secrets of your filesystem
Filesystems aren't generally something you're meant to notice. They're literally systems for defining a file. It's not the most exciting task a computer performs, and it's not something users are supposed to have to be concerned with. But some filesystems give you some fun, and safe, special abilities, and extended file attributes are a good example. Its use may be limited, but extended attributes are a unique way to add context to your data.
文件系统通常不是能引起你注意的东西。他们实际是定义文件的系统。这不是电脑做的最让人兴奋的任务也不是想让用户关注的东西。但是有些文件系统可以给你有趣安全且特殊的功能，扩展文件属性就是一个好例子。其的使用可能有限制，但是扩展属性是你增加数据中上下文环境的独特方法。
--------------------------------------------------------------------------------
@ -136,7 +125,7 @@ via: https://opensource.com/article/22/6/linux-attr-command
作者：[Seth Kenlon][a]
选题：[lkxed][b]
译者：[译者ID](https://github.com/译者ID)
译者：[wznmickey](https://github.com/wznmickey)
校对：[校对者ID](https://github.com/校对者ID)
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