PG::ConnectionBad - could not connect to server: Connection refused

For MacOS I use this:
```
brew info postgres
```
And in output in the most end, I see:
```
...
To have launchd start postgresql now and restart at login:
brew services start postgresql
Or, if you don't want/need a background service you can just run:
pg_ctl -D /usr/local/var/postgres start
```

So I just use this command `pg_ctl -D /usr/local/var/postgres start
` and `psql` begin work.

If removing `postmaster.pid` does not resolve the issue, this worked for me:

cd /usr/local/var/
rm -rf postgres/
mkdir postgres
initdb --locale=C -E UTF-8 postgres/
brew services restart postgresql

Credit to @spirito_libero 's solution on [this thread][1].


[1]:

[To see links please register here]

For me, it was really simple: I had a stale `postmaster.pid` file.

Simply deleting and restarting postgres fixed it for me:

```
rm '/Users/<username>/Library/Application Support/Postgres/var-10/postmaster.pid'
```

This occurred for me after upgrade Postgres (through Homebrew). I upgraded from version 12 to 13.

If this is the case for you try running `postgres -D /usr/local/var/postgres` and check the output. In my case it stated `database files are incompatible with server`.

You might get an error message that postgres.old already exists
```
Error: /usr/local/var/postgres.old already exists!
```

To fix that, just remove that file
```
rm -rf /usr/local/var/postgres.old
```

Fixing the database was as simple as running:
```
brew postgresql-upgrade-database
```

I have tried all of the answers above and it didn't work for me.

In my case when I chekced the log on `/usr/local/var/log/postgres.log`. It was fine no error. But I could see that it was listening my local IPV6 address which is `"::1"`

In my `database.yml` It was like this

```
host: <%= ENV['POSTGRESQL_ADDON_HOST'] || '127.0.0.1' %>
```

I changed it by


```
host: <%= ENV['POSTGRESQL_ADDON_HOST'] || 'localhost' %>
```

and then it worked

It could be as simple as a stale **PID file**. It could be failing silently because your computer didn't complete the shutdown process completely which means **postgres** didn't delete the **PID** (process id) file.

The PID file is used by postgres to make sure only one instance of the server is running at a time. So when it goes to start again, it fails because there is already a **PID** file which tells **postgres** that another instance of the server was started (even though it isn't running, it just didn't get to shutdown and delete the PID).

1. To fix it remove/rename the PID file. Find the postgres data directory. On macOS using homebrew it is in `/usr/local/var/postgres/`,
or `/usr/local/var/log/` other systems it might be `/usr/var/postgres/`. On M1, it might be `/opt/homebrew/var/postgresql`.
1. To make sure this is the problem, look at the log file (`server.log`). On the last lines you will see:

>FATAL: lock file "postmaster.pid" already exists<br>
>HINT: Is another postmaster (PID 347) running in data directory "/usr/local/var/postgres"?

3. If so, `rm postmaster.pid`
1. Restart your server. On a mac using launchctl (with homebrew) the following commands will restart the server.

brew services restart postgresql

OR on older versions of **Brew**

launchctl unload homebrew.mxcl.postgresql.plist
launchctl load -w homebrew.mxcl.postgresql.plist