使用ALTER USER命令修改用戶的密碼、密碼過期，鎖定，解鎖
（1）修改用戶的口令，將用戶的口令修改為新的密碼
highgo=#create user test with password ‘test’;
CREATEROLE
highgo=#select usename,passwd from pg_shadow;
usename | passwd
———+————————————-
highgo | md5614aeb636ab143b790547ce463ec1741
a | md5039af99d1e9a4b194e0eb800a6f8d018
b | md583aeaa4e529325e234e9c5c2e01e6c08
test | md505a671c66aefea124cc08b76ea6d30bb
(4rows)
highgo=#ALTER USER test with password ‘testnew’;
ALTERROLE
highgo=#select usename,passwd from pg_shadow;
usename | passwd
———+————————————-
highgo | md5614aeb636ab143b790547ce463ec1741
a | md5039af99d1e9a4b194e0eb800a6f8d018
b | md583aeaa4e529325e234e9c5c2e01e6c08
test | md57c56448e70f764f1ca97ceae33823c9b
(4rows)
（2）設置用戶口令過期，通過設置用戶過期，這樣該用戶在下次登錄的時候就必須要修改密碼。
highgo=# select usename,valuntil from pg_shadow;
usename | valuntil
———+———-
highgo |
a |
b |
test |
(4rows)
highgo=#alter user test with valid until ‘2017-4-4 12:48:00’;
ALTERROLE
highgo=#select usename,valuntil from pg_shadow;
usename | valuntil
———+————————
highgo |
a |
b |
test | 2017-04-04 12:48:00+08
(4rows)
此時遠程使用test連接數據庫將失敗。
（3）鎖定用戶，將用戶鎖定之后，被鎖定的用戶是不能夠再次登錄到系統中。
highgo=#ALTER USER test nologin;
ALTERROLE
highgo=#\c highgo test
致命錯誤: 不允許角色”test”進行登錄
致命錯誤: 不允許角色”test”進行登錄
Previousconnection kept
highgo=#
（4）解鎖用戶，解鎖用戶的鎖定狀態。
highgo=#ALTER USER test login;
ALTERROLE
highgo=#\c highgo test
Youare now connected to database “highgo” as user “test”.
highgo=>