Linux File Permissions settings

In Linux, for data security, permission control is very important, in this case can be subdivided into two parts to understand his

Permission definitions

Each user of Linux belongs to a group and cannot be independent of the group. Linux file permissions need to define three entities ' permissions on it

• File owner
• The group where the files are
• Other groups

Owner

Typically the creator of the file, who created the file, becomes the owner of the file naturally

You can use the Chown "Change owner" username file name to modify the owner of the file, such as changing the owner of the Error.log to Enoch

Chown Enoch Error.log #更改error the owner of the. Log is Enoch Chown enoch:home error.log #更改error. Log owner and user group for Enoch and home Chown The user group for the. Home Error.log #更改error. Log is used for home# in the owners and user groups. Yes, but because many users prefer to use the decimal point, which can cause system errors, it is recommended to use ":"

Your group

When a user creates a file, the group where the file is located is the user group that the user is in.

You can use the Chgrp "change group" to alter the group in which the file is located

chgrp Home Error.log #修改文件的所在组为home

Other groups

Except for groups other than the group are other groups

Permission Description

When we use the command ls-l, it will show the corresponding permission to change the file or folder.

2 www  www  4096 may  5:2   4096 may  5:wuyi  wwwlogsdrwxr34096 Jul  4: wwwroot

The first column specifies the file permission description, which consists of 10 characters divided into four parts, using the WWW directory

[d] [rwx] [---] [---]

1 234 567 890

1: Whether this file is a directory or a file name where D represents the directory, if the file is-, more file information is as follows

    d  directory file.    l  Symbolic link (pointing to another file, similar to a shortcut under plague).    s  socket file.    B  -block device file, binary file.    C  -character device file.    p  Name the pipe file.

234: File owner's permissions, rwx and readable writable executable

R (read, reading): For a file, have permission to read the contents of the file, and for the directory, have permission to browse the directory.  w(write, writes): For the file, with new, modified, delete the contents of the file permissions (do not include the deletion of the file); For the directory, with new, deleted, modified, Permission to move files within the directory (regardless of the file's permissions can be deleted). X (Execute, execute): For the file, it has permission to execute the file, and for the directory, the user has permission to enter the directory (you can use the CD command to enter the directory). 

567: File permissions for all groups,---represents no permissions

890: There is no permission here except for the owner and all users outside the group

Modify Permissions

The command to modify permissions is chmod, and the way to change permissions is divided into two

1. Number Change Permission method

Linux file basic permissions only nine, respectively, is onwer,group,other three kinds of identities, so we can use numbers to represent permissions, where

4 W 2  1

Each identity setting permission is an accumulation of numbers, such as setting the Error.log file to everyone with rwx permissions, then

chmod 777 Error.log

Because [-rwxrwxrwx] is actually [4+2+1][4+2+1][4+2+1] is 777. If we change the permission to [-rwxr-xr--] then [4+2+1][4+0+1][4+0+0] is 754

2. Symbol Change method

The symbolic change method is actually to set permissions on different entities, in which we can only understand the meaning of the three parts

chmod	U	+ (Join)	File or directory
	G	= (set)
	O
	A	-(remove)

Give a few examples to illustrate, set the user to Error.log have rwx permissions, the group and other groups have RX permissions.

chmod  U=rwx,go=rx  Error.log

Set the user to Error.log have rwx permissions, the group has the RX permission, the other groups have R permissions

chmod u=rwx,g=rx,o=r error.log

Out of the executable permissions for all users

chmod a-x error.log

Differences in Permissions

Linux File Permissions settings