Permissions explained in Linux

1, each file belongs to a user, a group
Can be queried by the $ ls-l/bin/bash command
$ ls-l/bin/bash
-rwxr-xr-x 1 root root 736348 2014-09-26/bin/bash

2. The Linux permissions model works by allowing three separate permission levels to be set for each file system object-they are the owner of the file, the group of files, and all other users.
-rwxr-xr-x 1 root root 736348 2014-09-26/bin/bash
As above rwxr is the owner-oriented XR is for the group system in the other user all rights X

3.-rwxr-xr-x a symbolic representation of the permission that contains the special file. The first character in the field (-) specifies the type of the file, in which case it is a regular file. Other possible first characters are:
"D" Directory
"L" symbolic link
"C" character specialized device file
"B" block specialized equipment files
"P" Advanced first Out
"S" sockets
eg
-rw-r--r--1 root root 0 04-15 14:26:1,.d
Drwxr-xr-x 4 Hadoop hadoop 4096 04-24 14:14 Desktop
DRWX------7 Hadoop hadoop 4096 04-13 23:30 Downloads
Drwxrwxr-x 5 Hadoop hadoop 4096 04-01 15:13 Flume
Drwxr-xr-x Hadoop hadoop 4096 03-31 19:30 Hadoop
Drwxrwxr-x 9 Hadoop hadoop 4096 04-13 12:57 Hive
Drwxr-xr-x 5 Hadoop hadoop 4096 04-12 15:35 java
Drwxrwxr-x 5 Hadoop hadoop 4096 04-13 23:38 Navicat110_mysql_cs
-rw-rw-r--1 Hadoop hadoop 52692169 04-13 20:24 navicat110_mysql_cs.tar.gz
-rw-r--r--1 Hadoop hadoop 04-15 13:31 Oracle account. txt
DRWXRWXRWX 9 Hadoop hadoop 4096 04-01 17:12 Splunk
Drwxr-xr-x Hadoop hadoop 4096 03-20 10:25 Tomcat
Drwxrwxr-x 5 Hadoop hadoop 4096 04-21 23:31 workspace

4. WhoAmI can view the currently logged in user
# WhoAmI
Root
# su Drobbins
$ whoami
Drobbins

5, group can see in which groups
Groups
Hadoop

If you want to see who else is in this group
Groups Hadoop
Hadoop:hadoop
Groups Root
Root:root bin Daemon Sys ADM disk wheel

6. All users or groups that change files or other file system objects must be super users
Grammar:
Chown root/u Change the owner of of/u to "root".
Chown root:staff/u Likewise, but also change it group to the "staff".
Chown-hr root/u Change the owner of of/u and subfiles to "root".

Chown root:wheel/etc/passwd

7. The chmod command is used to change the access rights of a file or directory.

Command Setup method
chmod [who] [+ |-| =] [mode] file name?
Action object who is either or their combination of the following letters:
U means "user", which is the owner of the file or directory.

G means "same group user", that is, all users with the same group ID as the file owner.

O means "other (others) users".

A means "all users". He is the system default value.

+ Add a permission.

-Cancels a permission.
= gives the given permission and cancels all other permissions, if any.
Setting the permissions represented by mode can be any combination of the following letters:
R is readable.

W writable.

X executable.

Digital Setting Method:
chmod [Number of Owner permissions] [number of user rights in group] [number of other user rights in system] file name?
Digital permission Meaning:
RWX 7
Rw-6
R-x 5
r--4
-WX 3
-w-2
--x 1
---0

Permissions explained in Linux