一、角色與用戶的區別
角色就相當于崗位：角色可以是經理，助理。
用戶就是具體的人：比如陳XX經理，朱XX助理，王XX助理。
在PostgreSQL 里沒有區分用戶和角色的概念，"CREATE USER" 為 "CREATE ROLE" 的別名，這兩個命令幾乎是完全相同的，唯一的區別是"CREATE USER" 命令創建的用戶默認帶有LOGIN屬性，而"CREATE ROLE" 命令創建的用戶默認不帶LOGIN屬性(CREATE USER is equivalent to CREATE ROLE except that CREATE USER assumes LOGIN by default, while CREATE ROLE does not)。
1.1 創建角色與用戶
CREATE ROLE 語法
CREATE ROLE name [ [ WITH ] option [ ... ] ]
where option can be:
SUPERUSER | NOSUPERUSER
| CREATEDB | NOCREATEDB
| CREATEROLE | NOCREATEROLE
| CREATEUSER | NOCREATEUSER
| INHERIT | NOINHERIT
| LOGIN | NOLOGIN
| REPLICATION | NOREPLICATION
| CONNECTION LIMIT connlimit
| [ ENCRYPTED | UNENCRYPTED ] PASSWORD 'password'
| VALID UNTIL 'timestamp'
| IN ROLE role_name [, ...]
| IN GROUP role_name [, ...]
| ROLE role_name [, ...]
| ADMIN role_name [, ...]
| USER role_name [, ...]
| SYSID uid
創建david 角色和sandy 用戶
postgres=# CREATE ROLE david; //默認不帶LOGIN屬性
CREATE ROLE
postgres=# CREATE USER sandy; //默認具有LOGIN屬性
CREATE ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | Cannot login | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=#
postgres=# SELECT rolname from pg_roles ;
rolname
----------
postgres
david
sandy
(3 rows)
postgres=# SELECT usename from pg_user; //角色david 創建時沒有分配login權限，所以沒有創建用戶
usename
----------
postgres
sandy
(2 rows)
postgres=#
1.2 驗證LOGIN屬性
postgres@CS-DEV:~> psql -U david
psql: FATAL: role "david" is not permitted to log in
postgres@CS-DEV:~> psql -U sandy
psql: FATAL: database "sandy" does not exist
postgres@CS-DEV:~> psql -U sandy -d postgres
psql (9.1.0)
Type "help" for help.
postgres=> /dt
No relations found.
postgres=>
用戶sandy 可以登錄，角色david 不可以登錄。
1.3 修改david 的權限，增加LOGIN權限
postgres=# ALTER ROLE david LOGIN ;
ALTER ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=# SELECT rolname from pg_roles ;
rolname
----------
postgres
sandy
david
(3 rows)
postgres=# SELECT usename from pg_user; //給david 角色分配login權限，系統將自動創建同名用戶david
usename
----------
postgres
sandy
david
(3 rows)
postgres=#
1.4 再次驗證LOGIN屬性
postgres@CS-DEV:~> psql -U david -d postgres
psql (9.1.0)
Type "help" for help.
postgres=> /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=>
david 現在也可以登錄了。
二、查看角色信息
psql 終端可以用/du 或/du+ 查看，也可以查看系統表 select * from pg_roles;
postgres=> /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | Cannot login | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=> /du+
List of roles
Role name | Attributes | Member of | Description
-----------+------------------------------------------------+-----------+-------------
david | Cannot login | {} |
postgres | Superuser, Create role, Create DB, Replication | {} |
sandy | | {} |
postgres=> SELECT * from pg_roles;
rolname | rolsuper | rolinherit | rolcreaterole | rolcreatedb | rolcatupdate | rolcanlogin | rolreplication | rolconnlimit | rolpassword | rolvaliduntil | rolconfig | oid
----------+----------+------------+---------------+-------------+--------------+-------------+----------------+--------------+-------------+---------------+-----------+-------
postgres | t | t | t | t | t | t | t | -1 | ******** | | | 10
david | f | t | f | f | f | f | f | -1 | ******** | | | 49438
sandy | f | t | f | f | f | t | f | -1 | ******** | | | 49439
(3 rows)
postgres=>
三、角色屬性（Role Attributes）
一個數據庫角色可以有一系列屬性，這些屬性定義了他的權限。
| 屬性 | 說明 |
| login | 只有具有 LOGIN 屬性的角色可以用做數據庫連接的初始角色名。 |
| superuser | 數據庫超級用戶 |
| createdb | 創建數據庫權限 |
| createrole | 允許其創建或刪除其他普通的用戶角色(超級用戶除外) |
| replication | 做流復制的時候用到的一個用戶屬性，一般單獨設定。 |
| password | 在登錄時要求指定密碼時才會起作用，比如md5或者password模式，跟客戶端的連接認證方式有關 |
| inherit | 用戶組對組員的一個繼承標志，成員可以繼承用戶組的權限特性 |
| ... | ... |
四、創建用戶時賦予角色屬性
從pg_roles 表里查看到的信息，在上面創建的david 用戶時，默認沒有創建數據庫等權限。
postgres@CS-DEV:~> psql -U david -d postgres
psql (9.1.0)
Type "help" for help.
postgres=> /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=> CREATE DATABASE test;
ERROR: permission denied to create database
postgres=>
如果要在創建角色時就賦予角色一些屬性，可以使用下面的方法。
首先切換到postgres 用戶。
4.1 創建角色bella 并賦予其CREATEDB 的權限。
postgres=# CREATE ROLE bella CREATEDB ;
CREATE ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB, Cannot login | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=#
4.2 創建角色renee 并賦予其創建數據庫及帶有密碼登錄的屬性。
postgres=# CREATE ROLE renee CREATEDB PASSWORD 'abc123' LOGIN;
CREATE ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB, Cannot login | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create DB | {}
sandy | | {}
postgres=#
4.3 測試renee 角色
a. 登錄
postgres@CS-DEV:~> psql -U renee -d postgres
psql (9.1.0)
Type "help" for help.
postgres=>
用renee 用戶登錄數據庫，發現不需要輸入密碼既可登錄，不符合實際情況。
b. 查找原因
在角色屬性中關于password的說明，在登錄時要求指定密碼時才會起作用，比如md5或者password模式，跟客戶端的連接認證方式有關。
查看pg_hba.conf 文件，發現local 的METHOD 為trust，所以不需要輸入密碼。
將local 的METHOD 更改為password，然后保存重啟postgresql。
c. 再次驗證
提示輸入密碼，輸入正確密碼后進入到數據庫。
d. 測試創建數據庫
創建成功。
五、給已存在用戶賦予各種權限
使用ALTER ROLE 命令。
ALTER ROLE 語法：
ALTER ROLE name [ [ WITH ] option [ ... ] ]
where option can be:
SUPERUSER | NOSUPERUSER
| CREATEDB | NOCREATEDB
| CREATEROLE | NOCREATEROLE
| CREATEUSER | NOCREATEUSER
| INHERIT | NOINHERIT
| LOGIN | NOLOGIN
| REPLICATION | NOREPLICATION
| CONNECTION LIMIT connlimit
| [ ENCRYPTED | UNENCRYPTED ] PASSWORD 'password'
| VALID UNTIL 'timestamp'
ALTER ROLE name RENAME TO new_name
ALTER ROLE name [ IN DATABASE database_name ] SET configuration_parameter { TO | = } { value | DEFAULT }
ALTER ROLE name [ IN DATABASE database_name ] SET configuration_parameter FROM CURRENT
ALTER ROLE name [ IN DATABASE database_name ] RESET configuration_parameter
ALTER ROLE name [ IN DATABASE database_name ] RESET ALL
5.1 賦予bella 登錄權限
a. 查看現在的角色屬性
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB, Cannot login | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create DB | {}
sandy | | {}
postgres=#
b. 賦予登錄權限
postgres=# ALTER ROLE bella WITH LOGIN;
ALTER ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create DB | {}
sandy | | {}
postgres=#
5.2 賦予renee 創建角色的權限
postgres=# ALTER ROLE renee WITH CREATEROLE;
ALTER ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create role, Create DB | {}
sandy | | {}
postgres=#
5.3 賦予david 帶密碼登錄權限
postgres=# ALTER ROLE david WITH PASSWORD 'ufo456';
ALTER ROLE
postgres=#
5.4 設置sandy 角色的有效期
postgres=# ALTER ROLE sandy VALID UNTIL '2014-04-24';
ALTER ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB | {}
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create role, Create DB | {}
sandy | | {}
postgres=# SELECT * from pg_roles ;
rolname | rolsuper | rolinherit | rolcreaterole | rolcreatedb | rolcatupdate | rolcanlogin | rolreplication | rolconnlimit | rolpassword | rolvaliduntil | rolconfig | oid
----------+----------+------------+---------------+-------------+--------------+-------------+----------------+--------------+-------------+------------------------+-----------+-------
postgres | t | t | t | t | t | t | t | -1 | ******** | | | 10
bella | f | t | f | t | f | t | f | -1 | ******** | | | 49440
renee | f | t | t | t | f | t | f | -1 | ******** | | | 49442
david | f | t | f | f | f | t | f | -1 | ******** | | | 49438
sandy | f | t | f | f | f | t | f | -1 | ******** | 2014-04-24 00:00:00+08 | | 49439
(5 rows)
postgres=#
六、角色賦權/角色成員
在系統的角色管理中，通常會把多個角色賦予一個組，這樣在設置權限時只需給該組設置即可，撤銷權限時也是從該組撤銷。在PostgreSQL中，首先需要創建一個代表組的角色，之后再將該角色的membership 權限賦給獨立的角色即可。
6.1 創建組角色
postgres=# CREATE ROLE father login nosuperuser nocreatedb nocreaterole noinherit encrypted password 'abc123';
CREATE ROLE
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB | {}
david | | {}
father | No inheritance | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create role, Create DB | {}
sandy | | {}
postgres=#
6.2 給father 角色賦予數據庫test 連接權限和相關表的查詢權限。
postgres=# GRANT CONNECT ON DATABASE test to father;
GRANT
postgres=# /c test renee
You are now connected to database "test" as user "renee".
test=> /dt
No relations found.
test=> CREATE TABLE emp (
test(> id serial,
test(> name text);
NOTICE: CREATE TABLE will create implicit sequence "emp_id_seq" for serial column "emp.id"
CREATE TABLE
test=> INSERT INTO emp (name) VALUES ('david');
INSERT 0 1
test=> INSERT INTO emp (name) VALUES ('sandy');
INSERT 0 1
test=> SELECT * from emp;
id | name
----+-------
1 | david
2 | sandy
(2 rows)
test=> /dt
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | emp | table | renee
(1 row)
test=> GRANT USAGE ON SCHEMA public to father;
WARNING: no privileges were granted for "public"
GRANT
test=> GRANT SELECT on public.emp to father;
GRANT
test=>
6.3 創建成員角色
test=> /c postgres postgres
You are now connected to database "postgres" as user "postgres".
postgres=# CREATE ROLE son1 login nosuperuser nocreatedb nocreaterole inherit encrypted password 'abc123';
CREATE ROLE
postgres=#
這里創建了son1 角色，并開啟inherit 屬性。PostgreSQL 里的角色賦權是通過角色繼承（INHERIT）的方式實現的。
6.4 將father 角色賦給son1
postgres=# GRANT father to son1;
GRANT ROLE
postgres=#
還有另一種方法，就是在創建用戶的時候賦予角色權限。
postgres=# CREATE ROLE son2 login nosuperuser nocreatedb nocreaterole inherit encrypted password 'abc123' in role father;
CREATE ROLE
postgres=#
6.5 測試son1 角色
postgres=# /c test son1
You are now connected to database "test" as user "son1".
test=> /dt
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | emp | table | renee
(1 row)
test=> SELECT * from emp;
id | name
----+-------
1 | david
2 | sandy
(2 rows)
test=>
用renee 角色新創建一張表，再次測試
test=> /c test renee
You are now connected to database "test" as user "renee".
test=> CREATE TABLE dept (
test(> deptid integer,
test(> deptname text);
CREATE TABLE
test=> INSERT INTO dept (deptid, deptname) values(1, 'ts');
INSERT 0 1
test=> /c test son1
You are now connected to database "test" as user "son1".
test=> SELECT * from dept ;
ERROR: permission denied for relation dept
test=>
son1 角色只能查詢emp 表的數據，而不能查詢dept 表的數據，測試成功。
6.6 查詢角色組信息
test=> /c postgres postgres
You are now connected to database "postgres" as user "postgres".
postgres=#
postgres=# /du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
bella | Create DB | {}
david | | {}
father | No inheritance | {}
postgres | Superuser, Create role, Create DB, Replication | {}
renee | Create role, Create DB | {}
sandy | | {}
son1 | | {father}
son2 | | {father}
postgres=#
“ Member of ” 項表示son1 和son2 角色屬于father 角色組。
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