Linux File and directory permissions

Linux File and directory permissions

View permissions for a file

The permissions for a file and directory, as shown below,

Localhost:workspace-github xinxingegeya$ ls-ltotal 8-rw-r--r--1 Xinxingegeya staff 8 19:10 a.htmldrwxr-xr-x 2 Xinxingegeya Staff 8 18:17 sample

A total of 10 digits, of which: the first one-represents the type

The three rw-in the middle represent the permissions owned by the owner (user)

Then the three r--represent the permissions that the group has.

The last three r--represent the rights that other people (other) have

which

R indicates that a file can be read (read)

W indicates that the file can be written (write)

x indicates that the file can be executed (if it is a program)

-Indicates that the appropriate permission has not been granted

Note: The directory problem to view file permissions: If you have a folder/a/b/c

The file that executes Ls-l/a/b view permission is not B, but the permission to view C.

Ls-l/A view of permissions for file B

Ls-l/a/b viewing permissions for C files

Ls-l/a/b/c viewing permissions for C files

Modify Permissions chmod command

The following actions,

Localhost:workspace-github xinxingegeya$ chmod o+w a.htmllocalhost:workspace-github xinxingegeya$ ls-ltotal 8- Rw-r--rw-1 Xinxingegeya Staff 8 19:10 a.htmldrwxr-xr-x 2 Xinxingegeya staff 8 18:17 sample

chmod o+w a.html means to increase the W permission for others, you can see that there is a W in the last three characters, which means that the permission of the other user is RW.

? ? chmod u+x filename here, u means user refers to users themselves; + means add permission; x refers to an executable file

Symbol mode

You can set multiple items using the symbol mode: Who (user type), operator (operator), and permission (permissions), and each item's settings can be separated by commas. The command chmod will modify the WHO-specified user type to access the file, and the user type is described by one or more letters in the WHO location, as shown in the WHO notation schema table:

W.H.O.	User Type	Description
U	User	File owner
G	Group	The group where the file owner resides
O	Others	All other users
A	All	Used by the user, equivalent to Ugo

Operator symbol Mode table:

Operator	Description
+	Add permissions for the specified user type
-	Remove permissions for a specified user type
=	Set the settings for the specified user right to reset all permissions for the user type

Permission symbol Mode table:

Mode	name	Description
R	Read	Set as readable permission
W	Write	Set to writable permission
X	Execute permissions	Set to executable permission
X	Special Execution permissions	File permission settings can only be performed if the file is a directory file, or if other types of users have executable permissions
S	Setuid/gid	When the file is executed, set the file's setuid or setgid permissions according to the user type specified by the WHO parameter
T	Paste bit	Set the paste bit, only the superuser can set the bit, only the file owner u can use that bit

Eight-binary syntax

The chmod command can use octal numbers to specify permissions. The permission bit of a file or directory is controlled by 9 permission bits, each of which is a set of three bits, which are read, write, execute, read, write, execute, and other users (other) of the file owner (user). Historically, file permissions were placed in a bitmask, with the bits specified in the mask set to 1, to indicate that a class had a corresponding priority.

chmod the octal syntax for the number description:

R 4

W 2

X 1

-0

The owner's authority is expressed in numbers: the sum of the numbers of the three permission bits of the master. such as rwx, that is, 4+2+1, should be 7.

The permissions of the user group are expressed in numbers: the sum of the number of permission bits that belong to the group. such as rw-, that is, 4+2+0, should be 6.

Other user's permission number expression: The sum of the numbers added to the other user's permission bits. such as R-x, that is, 4+0+1, should be 5.

Use this method to modify the permissions of the file,

Localhost:workspace-github xinxingegeya$ chmod 444 a.htmllocalhost:workspace-github xinxingegeya$ ls-ltotal 8- r--r--r--1 Xinxingegeya Staff 8 19:10 a.htmldrwxr-xr-x 2 Xinxingegeya staff 8 18:17 sample

chmod 444 a.html means that you only have read permissions and no other permissions.

Recursively modifying file permissions

The sample directory has a file b.html, recursively modifying the sample and b.html for the same permissions.

Localhost:workspace-github xinxingegeya$ chmod-r ug+rwx sample Localhost:workspace-github xinxingegeya$ ls-ltotal 8- r--r--r--1 Xinxingegeya Staff 8 19:10 a.htmldrwxrwxr--3 Xinxingegeya Staff 102 8 20:11 Samplelocalhost  : Workspace-github xinxingegeya$ cd samplelocalhost:sample xinxingegeya$ ls-ltotal 8-rwxrwxr--1 Xinxingegeya Staff 17 8 20:11 b.html

Chmod-r ug+rwx Sample

Recursively modifies the permissions of the sample directory and its files.

Reference: http://zhaoyuqiang.blog.51cto.com/6328846/1214718

Https://zh.wikipedia.org/wiki/Chmod

http://sweetpotato.blog.51cto.com/533893/1355372

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Linux File and directory permissions