Linux Operations note 20180001-File and directory management permissions

This period of time to think a lot, although preparation for postgraduate examination, but the final purpose is to work, so every day will take one hours to consolidate the small knowledge of operation and maintenance. I think the teacher told me a sentence is right, smart people will do two things at the same time. I have no blind self-confidence, after all, time and energy is limited, fixed three points of knowledge every day, I will insist on doing well. My notes basically from the network finishing, as a college student, I think the issue of copyright is not negotiable, in reference to other people's article, I will put the address of others, so that more people see, salute uncle, to those on the road of the programmer salute.

1.umask file default permissions (0022)

(1) Root User: Default 022

Files:-rw-r--r--

Catalog: Drwxr-xr-x

(2) General users: 002

usage: #umask-S U=rwx,g=rx,o=rx

2. File hidden properties chattr, lsattr

Chattr "+-=" "Asacdistu" file or directory Name "set file Properties"

Parameter: + Represents the addition of a special parameter, = represents only the following parameters (overwrite)

A: This file can only add data, cannot delete or modify data (root user can set).

I: "Do not kill permission". Files cannot be deleted, renamed, Connected, or can be written to or added to data (root).

Lsattr "AdR" file or directory "view file properties"

Parameter:-A: The properties of the hidden file are also shown.

-D: Lists only the properties of the directory itself.

-R: Along with the properties of the directory subdirectory are exposed.

3. Special permissions for Files suid, SGID, Sbit

(1) SUID ==> owner's permission

A.suid is valid only for binary programs, not for Shell script or directory

B. The performer needs to have X permission on the program

C. The performer will have the permissions of the program owner (owner)

　　　　　　

(2) SGID ==> Group permissions

A.sgid is valid only for binaries and can also be used in directories

B. The performer needs to have X permission on the program

C. The performer will have permissions for the program user group

(3) sbit sticky bit ==> other people

A.sbit only valid for directory

B. The performer needs to have W, x permissions on the directory, that is, permission to write.

C. When a user creates a file or directory under that directory, only himself and Root have the right to delete (their own) files, and in the same vein, they cannot delete others ' files.

Set suid, SGID, Sbit

corresponding 4 2 1 respectively

Example: Ls-l file "permissions to view Files"

chmod 4755 Test//Join has SUID permission

chmod 6755 Test//Permissions with Suid/sgid

chmod 1755 test//function with Sbit

chmod 7666 Test//has empty Suid/sgid permission performance as:--RWSRWSRWT

This chapter is taken from "Uncle Bird's private Cuisine Basics"

Linux Operations note 20180001-File and directory management permissions