Summary of knowledge points about file permissions in Linux learning

Any file in Linux hasthree permissions of "user, user group and other users". A user can belong to multiple user groups. All user related information is recorded in the/etc/passwdfile, passwords are recorded in the/etc/shaodwfile, and user groups are recorded in/etc/groupdocument.

The root user has the highest permissions, not counting other users

File attributes

ls -al -rw-r--r--@ 1 zhoust staff 58503 Dec 8 07:50 antigen.zsh drwxr-xr-x 2 zhoust staff 64 Apr 10 18:19 database drwxr-xr-x 6 zhoust staff 192 Apr 9 22:12 h5 drwxr-xr-x 4 zhoust staff 128 Nov 20 16:15 logs drwxr-xr-x 3 zhoust staff 96 Mar 18 17:42 node_modules -rw-r--r-- 1 zhoust staff 320 Mar 18 17:08 package-lock.json drwxr-xr-x 7 zhoust staff 224 Dec 8 07:20 software drwxr-xr-x 9 zhoust staff 288 Nov 20 16:32 store drwxr-xr-x 3 zhoust staff 96 Apr 4 15:43 vkds drwxr-xr-x 8 zhoust staff 256 Oct 23 15:06 照片 drwxr-xr-x 12 zhoust staff 384 Apr 19 08:36 学习视频

It is divided into seven parts:

1. File types and permissions
   File types: ordinary files (-), directory files (d), link files (l)
   Permissions: current user, same user group permissions and other user permissions, rwx is expressed in numbers as 421
2. How many file names are linked to this node (inode)
3. The user name that owns the file
4. The file User group to which it belongs
5. File size: Default is Byte
6. Creation time

7. File name

   Related tutorials:Linux video tutorial

rwx The meaning of files and directories

For files,wmeans that the content of the file can be modified (But does not include deleting files),xmeans that the file has the permission to be executed (whether it can be executed actually depends on the content of the file).

The directory is mainly responsible for recording the file name list

• r: means that the directory structure can be read
• w:Files (or directories) in this directory can be deleted, added, modified, moved, renamed, etc., with extremely high permissions
• x: Can enter This directory

If the user only has r permission on a certain directory, he can only view the file name and type in the directory, not even the file size and various attributes. For example, the zst user only has read permissions for the/home/zhoustdirectory and can only see the file names in this directory.

[zhoust@MyPersonalCentOS ~]$ ls -al total 36 drwxr-xr-- 5 zhoust zhoust 4096 Apr 21 14:55 . [zst@MyPersonalCentOS ~]$ ls -l /home/zhoust/ ls: cannot access /home/zhoust/learn: Permission denied total 0 d????????? ? ? ? ? ? learn

The minimum permissions to complete the task

If the user does not have x permissions on a directory, he cannot execute any commands in the directory, nor can he query the contents of files in the directory.

##Read the contents of file1 x r - Modify the content of file1 x rw - can be entered and modified Delete file1 file wx - - Be able to enter /dir1 and have directory modification permissions That’s it! Copy file1 to /dir2 x #r wx Must be able to read file1 and be able to Modify the data in /dir2 ##Modify file attributes and permissions

Operation action	/dir1	/dir1/file1	/dir2	Explanation
				You must be able to enter /dir1 to read the file data inside!

Three commands,

chown

,chgrp,chmodrespectively represent the user to whom the modified file belongs, the user group to which the modified file belongs, and the modified file permissions

chmod

There are two types of syntax, one is to modify with numbers , the other is to use symbols to modify file permissions.Use numbers to modify, respectively

421

Add the numbers at the corresponding positions, for example:

# 在 /home/zhoust 目录下，其他用户都不可进入 [zhoust@MyPersonalCentOS ~]$ ls -al drwxrwxr-x 2 zhoust zhoust 4096 Apr 21 14:55 learn [zst@MyPersonalCentOS ~]$ cd /home/zhoust/ bash: cd: /home/zhoust/: Permission denied # 使用 chmod 修改为其他用户可进入，zst 就能进入这个目录了 [zhoust@MyPersonalCentOS ~]$ chmod 705 . [zhoust@MyPersonalCentOS ~]$ ls -al drwx---r-x 5 zhoust zhoust 4096 Apr 21 14:55 .

Use symbol type to modify file permissions, the format is

[ Scope][Modify][A certain permission]

,ubelongs to the user,guser group,oother users,aall users , the symbols used for modification are-=, and the permissions are still the threerwx. Now turn off other user permissions of the/home/zhoustdirectory:

[zhoust@MyPersonalCentOS ~]$ chmod o-rx . [zhoust@MyPersonalCentOS ~]$ ls -al total 36 drwx------ 5 zhoust zhoust 4096 Apr 21 14:55 .

The above is the detailed content of Summary of knowledge points about file permissions in Linux learning. For more information, please follow other related articles on the PHP Chinese website!