Fedora 26下Phoenix与PostgreSQL连接认证失败问题求助

Let’s get this sorted out—you’re hitting PostgreSQL’s default Ident authentication restriction, which is why Phoenix can’t connect even though you know the postgres user password. Here’s how to fix it step by step:

Why this happens #

PostgreSQL uses Ident authentication for local connections by default, which matches your operating system username directly to a PostgreSQL username. Since you’re running Phoenix as your regular user (not the postgres system user), it can’t pass this check. We need to switch to password-based authentication (md5) for the postgres user to let Phoenix connect properly.

Step 1: Edit PostgreSQL’s authentication config file #

First, open the pg_hba.conf file—on Fedora 26, it lives at /var/lib/pgsql/data/pg_hba.conf. You’ll need sudo permissions to edit it:

sudo nano /var/lib/pgsql/data/pg_hba.conf

Look for the lines handling local connections for the postgres user. You’ll probably see something like this:

local   all             postgres                                ident

Or for TCP loopback connections:

host    all             all             127.0.0.1/32            ident

Change the ident value to md5 in these lines. For example:

local   all             postgres                                md5
host    all             all             127.0.0.1/32            md5

Save the file (in nano, that’s Ctrl+O then Ctrl+X).

Step 2: Restart PostgreSQL to apply changes #

The new authentication rules won’t take effect until you restart the service:

sudo systemctl restart postgresql

Step 3: Double-check your Phoenix Repo configuration #

Make sure your config/dev.exs has the correct credentials for Hello.Repo—it should match your postgres user details:

config :hello, Hello.Repo,
  username: "postgres",
  password: "postgres",
  database: "hello_dev",
  hostname: "localhost",
  show_sensitive_data_on_connection_error: true,
  pool_size: 10

Step 4: Run mix ecto.create again #

Now go ahead and run the command once more:

mix ecto.create

This should let Phoenix authenticate with the postgres user using your password and create the database without issues.

内容的提问来源于stack exchange，提问作者Matt Stevens