linux[basic]-20-user and file permissions-[File hidden permissions]-[02]

Hidden Permissions for files

The permissions of a file have a special permission in addition to reading , writing , and SUID,SGID,sbit .

For example: you have permission to delete a file and cannot delete it, or you can only

To append content to a file and not to reduce or modify it, this will

Suspected of being attached with hidden permissions

chattr command to set hidden permissions for a file

Format:chattr [parameter] file

Parameters	Role
I	will not be able to modify the file, if the directory modified only can be modified but not new \ Delete
A	Allow append only (append), cannot overwrite, delete (append only)
S	Sync to hard drive immediately after file contents are modified
S	Completely removed from the hard drive, unrecoverable (with 0 filling the area of the hard disk where the original file resides)
A	The last access time for this file is not modified (atime)
B	Do not modify the file or directory access time
D	Check for errors in compressed files
D	Ignore this file/directory when using the dump command backup
C	The default is to compress files/directories
U	Save data on your hard drive after deleting this file for easy recovery
T	Let file system support trailer merge (tail-merging)
X	The contents of the compressed file can be accessed directly

lsattr command to display hidden permissions for a file

Format:lsattr [parameter] file

Parameters	Role
A	Show All files and directories
L	Displays the full name of the hidden property (the default is the abbreviated letter)
R	Recursive processing (processing all files and subdirectories under the specified directory)
D	If the target is a directory, add this parameter

Instance:

[Email protected] test1]#

[Email protected] test1]# echo "for test" > Test #创建一个文件

[Email protected] test1]# RM Test #删除

Rm:remove regular file ' test '? Y

[Email protected] test1]# echo "for test" > Test #在创建一个文件

[[email protected] test1]# chattr +a test #附加一个隐藏权限 (append only)

[[Email protected] test1]# RM test #删除, display cannot be deleted

Rm:remove regular file ' test '? Y

Rm:cannot remove ' test ': Operation not permitted

[Email protected] test1]# ll-a test #ls See nothing unusual

-rw-r--r--. 1 root root 9 Sep 15:58 test

[[email protected] test1]# lsattr-a test #lsattr view hidden permissions

-----a----------Test

[[email protected] test1]# chattr-a test #chattr Remove Permissions

[[Email protected] test1]# RM test #删除, and found can delete

Rm:remove regular file ' test '? Y

[[email protected] test1]# ls

[Email protected] test1]#

linux[Basic]-20-User and file permissions--[File hidden permissions]-[02]