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The chattr command is used to set hidden permissions for files in the format "chattr [parameters] file". If you want to add a hidden function to a file, you need to append "+ parameter" to the command, and if you want to remove a hidden function from the file, you need to append "- parameter".

Linux chattr command

In general, the "chattr" command is used to change properties on a Linux file. Here is its syntax:

Chattr [- RVf] [- v version] [mode] files...

Here is a description of it in the man manual:

Chattr changes file properties on a Linux file system.

A common format is: +-= [aAcCdDeijsStTu]

The'+ 'option adds attributes to the file; the'-'option removes attributes from the file; and the' = 'option makes the file have only these attributes.

The letter 'aAcCdDeijsStTu' can give new attributes to the file:

A: only data can be attached

A: do not modify the access time

C: compress the file

C: copy on write is not performed (COW). When multiple callers get the same resource, another caller modifies the resource and does not generate a copy of the

D: no dump

D: synchronously update the directory

E:extent format (a file system format)

I: it cannot be modified. You cannot delete or rename, create a link to the file, or write data to the file. Only superusers or processes with CAP_LINUX_IMMUTABLE capabilities can set or clear this property.

J: data log

S: secure deletion

S: synchronous updates

T: do not know the tail merge of the file

T: when the u: file at the top of the directory hierarchy is deleted, its contents are saved and can be restored later

The following read-only properties can be listed using lsattr, but cannot be modified by chattr

E: compression error

H: huge files

I: index catalog

N: inline data

X: compress the original access

Z: the compressed file is dirty

Not all file systems support all flags; refer to the file system manual for more details on file formats such as btrfs (5), ext4 (5), and xfs (5).

Here are some question-and-answer examples that should give you a good idea of how chattr commands work.

Q1. How to use the chattr command?

Suppose you want to make a file read-only. So all you have to do is run the chattr command with the + I option and the name of the file as parameters.

Such as:

Chattr + I test.txt

The screenshot below shows that once you use chattr to become a read-only file, no other operation will succeed on the file.

Note: as you have already observed, you need to have root permission to use the chattr command.

Q2. How does the chattr command cancel the read-only attribute?

It's simple-all you have to do is replace + I with the-I option. For example:

Chattr-I test.txt

Q3. How does the chattr command add permissions to a file that can only be append-only?

Sometimes, you may not want to impose full restrictions on files. I mean, you may want to provide users with additional access to files so that new content can be added, but existing content cannot be deleted or edited. This can also be done through the + an option.

Chattr + a test.txt

You can now attach content to the file, but you cannot edit the existing information in the file or delete the file. To cancel this behavior, simply use the-an option.

Chattr-a test.txt

Q4. How does the chattr command add restrictions to all files in a directory?

This can be done using the tag-R, which allows you to recursively change the properties of the directory and its contents. For example, if you want all files in the test-dir directory to be read-only, use the following methods:

Chattr-R + I. / test-dir/

The screenshot below shows that the read-only limit has been successfully applied to all files in the directory.

Q5. How do I view the properties on a file assigned by the chattr command?

So far, to check whether the chattr directory has been executed successfully, we have tried to perform some operations, such as editing the file or deleting it. But there is a separate command that allows you to easily see if the file has an attribute. The command is lsattr.

Lsattr [FILENAME]

For example, the screenshot below shows the output of lsattr, which clearly shows that the "I" attribute is applied to all files in the directory.

Again, this is the output after using the-I option.

As you can see in the screenshot above, the read-only attribute has been removed from all files.

Thank you for your reading, the above is the "Linux chattr command use case analysis" content, after the study of this article, I believe you have a deeper understanding of the Linux chattr command use example analysis of this problem, the specific use also needs to be verified by practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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