psql 没有提示我输入密码，然后拒绝访问

我在 Debian Linux 上使用 Postgres 9.4。我用一个用户创建了一个数据库，cindex可以访问该数据库。然而，当我尝试在命令行登录时，我什至没有提示输入密码：

myuser@myuserserver:~ $ psql -Ucindex cindex
psql: FATAL:  Peer authentication failed for user "cindex"

我还需要做什么才能启用用户？下面你可以看到我已经设置的权限：

postgres@myuserserver:~$ psql
psql (9.4.13)
Type "help" for help.

postgres=# GRANT SELECT ON ALL TABLES IN SCHEMA cindex TO cindex;
GRANT
postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 cindex    | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =T/postgres          +
           |          |          |             |             | postgres=CTc/postgres+
           |          |          |             |             | cindex=c/postgres
 postgres  | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 |
 template0 | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
(4 rows)

postgres=# \du
                             List of roles
 Role name |                   Attributes                   | Member of
-----------+------------------------------------------------+-----------
 cindex    |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}