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TSL&PRF
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Xingyu Wang
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Introduction to the Linux chown command)
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[#]: via: (https://opensource.com/article/19/8/linux-chown-command)
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[#]: author: (Alan Formy-Duval https://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/greg-phttps://opensource.com/users/alanfdoss)
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Introduction to the Linux chown command
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======
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Learn how to change a file or directory's ownership with chown.
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![Hand putting a Linux file folder into a drawer][1]
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Every file and directory on a Linux system is owned by someone, and the owner has complete control to change or delete the files they own. In addition to having an owning _user_, a file has an owning _group_.
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You can view the ownership of a file using the **ls -l** command:
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```
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[pablo@workstation Downloads]$ ls -l
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total 2454732
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-rw-r--r--. 1 pablo pablo 1934753792 Jul 25 18:49 Fedora-Workstation-Live-x86_64-30-1.2.iso
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```
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The third and fourth columns of the output are the owning user and group, which together are referred to as _ownership_. Both are **pablo** for the ISO file above.
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The ownership settings, set by the [**chmod** command][2], control who is allowed to perform read, write, or execute actions. You can change ownership (one or both) with the **chown** command.
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It is often necessary to change ownership. Files and directories can live a long time on a system, but users can come and go. Ownership may also need to change when files and directories are moved around the system or from one system to another.
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The ownership of the files and directories in my home directory are my user and my primary group, represented in the form **user:group**. Suppose Susan is managing the Delta group, which needs to edit a file called **mynotes**. You can use the **chown** command to change the user to **susan** and the group to **delta**:
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```
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$ chown susan:delta mynotes
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ls -l
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-rw-rw-r--. 1 susan delta 0 Aug 1 12:04 mynotes
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```
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Once the Delta group is finished with the file, it can be assigned back to me:
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```
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$ chown alan mynotes
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$ ls -l mynotes
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-rw-rw-r--. 1 alan delta 0 Aug 1 12:04 mynotes
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```
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Both the user and group can be assigned back to me by appending a colon (**:**) to the user:
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```
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$ chown alan: mynotes
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$ ls -l mynotes
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-rw-rw-r--. 1 alan alan 0 Aug 1 12:04 mynotes
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```
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By prepending the group with a colon, you can change just the group. Now members of the **gamma** group can edit the file:
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```
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$ chown :gamma mynotes
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$ ls -l
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-rw-rw-r--. 1 alan gamma 0 Aug 1 12:04 mynotes
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```
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A few additional arguments to chown can be useful at both the command line and in a script. Just like many other Linux commands, chown has a recursive argument ****(**-R**) which tells the command to descend into the directory to operate on all files inside. Without the **-R** flag, you change permissions of the folder only, leaving the files inside it unchanged. In this example, assume that the intent is to change permissions of a directory and all its contents. Here I have added the **-v** (verbose) argument so that chown reports what it is doing:
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```
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$ ls -l . conf
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.:
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drwxrwxr-x 2 alan alan 4096 Aug 5 15:33 conf
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conf:
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-rw-rw-r-- 1 alan alan 0 Aug 5 15:33 conf.xml
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$ chown -vR susan:delta conf
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changed ownership of 'conf/conf.xml' from alan:alan to susan:delta
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changed ownership of 'conf' from alan:alan to susan:delta
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```
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Depending on your role, you may need to use **sudo** to change ownership of a file.
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You can use a reference file (**\--reference=RFILE**) when changing the ownership of files to match a certain configuration or when you don't know the ownership (as might be the case when running a script). You can duplicate the user and group of another file (**RFILE**, known as a reference file), for example, to undo the changes made above. Recall that a dot (**.**) refers to the present working directory.
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```
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`$ chown -vR --reference=. conf`
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```
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### Report Changes
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Most commands have arguments for controlling their output. The most common is **-v** (-**-verbose**) to enable verbose, but chown also has a **-c** (**\--changes**) argument to instruct chown to only report when a change is made. Chown still reports other things, such as when an operation is not permitted.
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The argument **-f** (**\--silent**, **\--quiet**) is used to suppress most error messages. I will use **-f** and the **-c** in the next section so that only actual changes are shown.
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### Preserve Root
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The root (**/**) of the Linux filesystem should be treated with great respect. If a mistake is made at this level, the consequences could leave a system completely useless. Particularly when you are running a recursive command that makes any kind of change or worse: deletions. The chown command has an argument that can be used to protect and preserve the root. The argument is **\--preserve-root**. If this argument is used with a recursive chown command on the root, nothing is done and a message appears instead.
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```
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$ chown -cfR --preserve-root alan /
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chown: it is dangerous to operate recursively on '/'
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chown: use --no-preserve-root to override this failsafe
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```
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The option has no effect when not used in conjunction with **\--recursive**. However, if the command is run by the root user, the permissions of the **/** itself will be changed, but not of other files or directories within.
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```
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$ chown -c --preserve-root alan /
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chown: changing ownership of '/': Operation not permitted
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[root@localhost /]# chown -c --preserve-root alan /
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changed ownership of '/' from root to alan
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```
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### Ownership is security
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File and directory ownership is part of good information security, so it's important to occasionally check and maintain file ownership to prevent unwanted access. The chown command is one of the most common and important in the set of Linux security commands.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/19/8/linux-chown-command
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作者：[Alan Formy-Duval][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/greg-phttps://opensource.com/users/alanfdoss
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/yearbook-haff-rx-linux-file-lead_0.png?itok=-i0NNfDC (Hand putting a Linux file folder into a drawer)
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[2]: https://opensource.com/article/19/8/introduction-linux-chmod-command
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@ -0,0 +1,131 @@
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: (wxy)
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Introduction to the Linux chown command)
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[#]: via: (https://opensource.com/article/19/8/linux-chown-command)
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[#]: author: (Alan Formy-Duval https://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/greg-phttps://opensource.com/users/alanfdoss)
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chown 命令简介
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======
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> 学习如何使用 chown 命令更改文件或目录的所有权。
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![Hand putting a Linux file folder into a drawer][1]
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Linux 系统上的每个文件和目录均由某个人拥有，拥有者可以完全控制更改或删除他们拥有的文件。除了有一个*拥有用户*外，文件还有一个*拥有组*。
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你可以使用 `ls -l` 命令查看文件的所有权：
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```
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[pablo@workstation Downloads]$ ls -l
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total 2454732
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-rw-r--r--. 1 pablo pablo 1934753792 Jul 25 18:49 Fedora-Workstation-Live-x86_64-30-1.2.iso
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```
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该输出的第三和第四列是拥有用户和组，它们一起称为*所有权*。上面的那个 ISO 文件这两者都是 `pablo`。
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所有权设置由 [chmod 命令][2]进行设置，控制允许谁可以执行读取、写入或运行的操作。你可以使用 `chown` 命令更改所有权（一个或两者）。
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所有权经常需要更改。文件和目录一直存在在系统中，但用户不断变来变去。当文件和目录在系统中移动时，或从一个系统移动到另一个系统时，所有权也可能需要更改。
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我的主目录中的文件和目录的所有权是我的用户和我的主要组，以 `user:group` 的形式表示。假设 Susan 正在管理 Delta 组，该组需要编辑一个名为 `mynotes` 的文件。你可以使用 `chown` 命令将该文件的用户更改为 `susan`，组更改为 `delta`：
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```
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$ chown susan:delta mynotes
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ls -l
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-rw-rw-r--. 1 susan delta 0 Aug 1 12:04 mynotes
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```
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当给该文件设置好了 Delta 组时，它可以分配回给我：
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```
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$ chown alan mynotes
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$ ls -l mynotes
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-rw-rw-r--. 1 alan delta 0 Aug 1 12:04 mynotes
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```
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给用户后添加冒号（`:`），可以将用户和组都分配回给我：
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```
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$ chown alan: mynotes
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$ ls -l mynotes
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-rw-rw-r--. 1 alan alan 0 Aug 1 12:04 mynotes
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```
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通过在组前面加一个冒号，可以只更改组。现在，`gamma` 组的成员可以编辑该文件：
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```
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$ chown :gamma mynotes
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$ ls -l
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-rw-rw-r--. 1 alan gamma 0 Aug 1 12:04 mynotes
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```
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`chown` 的一些附加参数都能用在命令行和脚本中。就像许多其他 Linux 命令一样，`chown` 有一个递归参数（`-R`），它告诉该命令进入目录以对其中的所有文件进行操作。没有 `-R` 标志，你就只能更改文件夹的权限，而不会更改其中的文件。在此示例中，假定目的是更改目录及其所有内容的权限。这里我添加了 `-v`（详细）参数，以便 `chown` 报告其工作情况：
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```
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$ ls -l . conf
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.:
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drwxrwxr-x 2 alan alan 4096 Aug 5 15:33 conf
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conf:
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-rw-rw-r-- 1 alan alan 0 Aug 5 15:33 conf.xml
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$ chown -vR susan:delta conf
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changed ownership of 'conf/conf.xml' from alan:alan to susan:delta
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changed ownership of 'conf' from alan:alan to susan:delta
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```
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根据你的角色，你可能需要使用 `sudo` 来更改文件的所有权。
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在更改文件的所有权以匹配特定配置时，或者在你不知道所有权时（例如运行脚本时），可以使用参考文件（`--reference=RFILE`）。例如，你可以复制另一个文件（`RFILE`，称为参考文件）的用户和组，以撤消上面所做的更改。回想一下，点（`.`）表示当前的工作目录。
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```
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$ chown -vR --reference=. conf
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```
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### 报告更改
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大多数命令都有用于控制其输出的参数。最常见的是 `-v`（`--verbose`）以启用详细信息，但是 `chown` 还具有 `-c`（`--changes`）参数来指示 `chown` 仅在进行更改时报告。`chown` 还会报告其他情况，例如不允许进行的操作。
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参数 `-f`（`--silent`、`--quiet`）用于禁止显示大多数错误消息。在下一节中，我将使用 `-f` 和 `-c`，以便仅显示实际更改。
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### 保持根目录
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Linux 文件系统的根目录（`/`）应该受到高度重视。如果命令在此层级上犯了一个错误，则后果可能会使系统完全无用。尤其是在运行一个会递归修改甚至删除的命令时。`chown` 命令具有一个可用于保护和保持根目录的参数，它是 `--preserve-root`。如果在根目录中将此参数和递归一起使用，那么什么也不会发生，而是会出现一条消息：
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```
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$ chown -cfR --preserve-root alan /
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chown: it is dangerous to operate recursively on '/'
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chown: use --no-preserve-root to override this failsafe
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```
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如果不与 `--recursive` 结合使用，则该选项无效。但是，如果该命令由 `root` 用户运行，则 `/` 本身的权限将被更改，但其下的其他文件或目录的权限则不会更改：
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```
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$ chown -c --preserve-root alan /
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chown: changing ownership of '/': Operation not permitted
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[root@localhost /]# chown -c --preserve-root alan /
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changed ownership of '/' from root to alan
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```
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### 所有权即安全
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文件和目录所有权是良好的信息安全性的一部分，因此，偶尔检查和维护文件所有权以防止不必要的访问非常重要。`chown` 命令是 Linux 安全命令集中最常见和最重要的命令之一。
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/19/8/linux-chown-command
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作者：[Alan Formy-Duval][a]
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选题：[lujun9972][b]
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译者：[wxy](https://github.com/wxy)
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校对：[wxy](https://github.com/wxy)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/alanfdosshttps://opensource.com/users/sethhttps://opensource.com/users/greg-phttps://opensource.com/users/alanfdoss
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/yearbook-haff-rx-linux-file-lead_0.png?itok=-i0NNfDC (Hand putting a Linux file folder into a drawer)
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[2]: https://opensource.com/article/19/8/introduction-linux-chmod-command
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