Chmod for Ubuntu Linux commands [conversion]

Usage: chmod [-CFVR] [-- help] [-- version] mode file...

Note: file access permissions for Linux/Unix are classified into three levels: file owner, group, and others. Chmod can be used to control how files are accessed by others.

Mode: permission setting string in the following format: [ugoa...] [[+-=] [rwxx]...] [,...], U indicates the owner of the file, G indicates that the owner of the file belongs to the same group, O indicates that the owner of the file belongs to other people, and a indicates that all three are.
+ Adds a permission,-Indicates canceling the permission, and = indicates a unique permission.
R indicates that the file can be read, W indicates that the file can be written, and X indicates that the file can be executed only when the file is a subdirectory or the file has been set to executable.
-C: if the permission of the file has been changed, the change action is displayed.
-F: Do not display an error message if the file permission cannot be changed.
-V: displays details of permission changes.
-R: Change the permissions of all files and sub-directories in the current directory in the same way (that is, change one by one in the way of delivery)
-- Help: displays auxiliary instructions
-- Version: displays the version.

Example: Set the file file1.txt to readable by all users:
Chmod Ugo + R file1.txt

Set file1.txt to readable:
Chmod A + R file1.txt

Set file1.txt and file2.txt as the owner of the archive, which can be written to the same group to which the archive belongs, but not to others:
Chmod ug + W, o-w file1.txt file2.txt

Set ex1.py to only the owner of the file to execute:
Chmod U + x ex1.py

Set all files and subdirectories in the current directory to be readable by anyone:
Chmod-r a + R *

In addition, chmod can use numbers to indicate permissions, such as chmod 777 file.
Syntax: chmod ABC File

Each A, B, and C is a number, indicating the permissions of the user, group, and other respectively.

R = 4, W = 2, x = 1
If you want the rwx attribute, 4 + 2 + 1 = 7;
If the RW-attribute is required, 4 + 2 = 6;
If you want the R-x attribute, 4 + 1 = 7.

Example:
Chmod A = rwx File

And
Chmod 777 File

Same effect
Chmod ug = rwx, O = X file

And
Chmod 771 File

Same effect

If you use chmod 4755 filename, you can grant root permissions to this program.
Command name: chown
Permission: Root

Usage: chmod [-cfhvr] [-- help] [-- version] user [: Group] file...

Note: Linux/Unix is a multi-person, multi-job operating system. All archives have owners. Chown can be used to change the owner of an archive. Generally, this command is only used by the system administrator (Root). Generally, users do not have the permission to change the owner of another user's archive or change their owner to another user. Only the system administrator (Root) has such permissions.

Calculation:

User: User idgroup of the new owner: User Group of the new owner (Group)-C: if the owner of the file has indeed changed, the change action is displayed-F: if the archive owner cannot be changed, do not display the error message-H: only the link is changed, not the file that the link actually points to-V: show owner change details-R: perform the same owner change on all files in the current directory and sub-directories (I .e., change one by one in the way of delivery) -- help: show auxiliary description -- version: display version

Example:
Set the owner of the file file1.txt to user Jessie of the Users Group:
Chown JESSIE: Users file1.txt

Set all files in the current directory and sub-directory owner to user Lamport of Users Group:
Chmod-r Lamport: Users *
-RW ------- (600) -- only the owner has read and write permissions.

-RW-r -- (644) -- only the owner has read and write permissions, while the owner and other users have only read permissions.

-Rwx ------ (700) -- only the owner has read, write, and execution permissions.

-Rwxr-XR-X (755)-the owner has the read, write, and execution permissions, while the owner and other users have only the read and execution permissions.

-Rwx -- X (711) -- the owner has read, write, and execution permissions, while the owner and other users have only execution permissions.

-RW-(666) -- all users have the permission to read and write files. This approach is not advisable.

-Rwxrwxrwx (777)-all users have read, write, and execute permissions. It is not advisable.

The following are two common settings for the directory:

Drwx ------ (700)-only the owner can read and write data in the directory.

drwxr-XR-X (755)-All users can read the directory, but only the owner can change the content in the directory.
the SUID represents 4, for example, the result of 4755 is-rwsr-XR-x
the sgid represents 2, for example, the result of 6755 is-rwsr-Sr-x
the sticky digit indicates that the number is 1. For example, the result of 7755 is-rwsr-Sr-tvv

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