为什么 postgres 以 hostname = /var/run/postgresql 运行？

Question

I've been trying to get pg to connect to my local postgres instance using

const pool = new Pool({
  user: "my_user",
  host: "localhost",
  database: "my_db",
  password: "password",
  port: 5432,
});

but it never worked, and I repeatedly got an error saying error: Ident authentication failed for user "my_user" . I fiddled around with postgres users/roles for a while to make sure my_user owned the db and the tables, but then I noticed psql -d my_db -U my_user -h localhost failed with the same error as above. After some searching I found that using

host: "/var/run/postgresql"

fixed the problem, but I'm not sure I understand why. Should I be able to use localhost ? It seems like it's the default for most people setting these things up. I'm on Fedora 33, and only just installed postgres, so maybe it has something to do with it being a fresh install?

Answer 1

You have your pg_hba.conf set up to use "ident" authentication for connections coming from localhost. I don't think is a very common configuration. I don't think that would be the default and I don't know why you would have edited it to make it do that, but apparently that is what has happened. (In my hands, merely installing the database software on fedora 33 doesn't automatically create the database, you have to something to make that happen. If you followed a tutorial, please link to it)

If you want to use "ident" authentication, then look in the log file to see why it is failing, and then fix it (maybe you need to install oidentd?). If you don't want to use it, then edit pg_hba so you are not using "ident".

Answer 2

It is possible that PostgreSQL is not configured to allow this user to connect via TCP, only UNIX sockets. Check the pg_hba.conf of your Postgres install - it should contain an entry that allows my_user to access my_db from host 127.0.0.1/32. Broader allowances may be used in its place.

The file will usually contain many helpful examples that are commented out by default, but if in doubt, consult the manual: https://www.postgresql.org/docs/current/auth-pg-hba-conf.html

The defaults that Postgres is shipped with may depend on the Linux distribution / package repository that you use.