Postgresql server starts in nix-shell but I can't use it (connection failed)

Question

I want to run postgresql within a nix-shell. I followed the instructions on this page: https://mgdm.net/weblog/postgresql-in-a-nix-shell/

PostgreSQL installs properly in the shell (it's not installed on the main system at all), and I can start the server:

[nix-shell:~/Prog/Rust/ibis]$ pg_ctl -D .tmp/mydb -l logfile -o "--unix_socket_directories='$PWD'" start waiting for server to start.... done server started

But then if I try to create a database it gives me an error about connection on server socket. I tried two ways and they give the same error:

[nix-shell:~/Prog/Rust/ibis]$ createdb mydb createdb: error: connection to server on socket "/run/postgresql/.s.PGSQL.5432" failed: No such file or directory Is the server running locally and accepting connections on that socket?

and

[nix-shell:~/Prog/Rust/ibis]$ psql -c "CREATE USER ibis WITH PASSWORD 'censored' SUPERUSER;" -U postgres psql: error: connection to server on socket "/run/postgresql/.s.PGSQL.5432" failed: No such file or directory Is the server running locally and accepting connections on that socket?

I have created a /run/postgresql/ folder within the project folder. I used chmod to give full permissions to all.

What am I not understanding here? I can start and stop the server, and the folder exists within the project folders.

In postgresql.conf per Connection settings is port set to something other then 5432 and what is listen_addresses set to. Add answers as text update to question text. — Adrian Klaver
– Adrian Klaver, Commented Oct 22 at 19:19

Laurenz Albe · Accepted Answer · 2025-10-22 20:23:58Z

1

Well, if you created the Unix socket in $PWD, you cannot expect it to be in the location configured by postgresql.conf or the default location.

Try

createdb --host=$PWD mydb

edited Oct 22 at 20:23

answered Oct 22 at 19:29

Laurenz Albe

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2 Comments

Matt Payne Oct 22 at 19:57

> Your are just horsing around and experimenting, right? Not just messing around, but I've never used nix-shell before.

Laurenz Albe Oct 22 at 20:23

No problem with that, I was just curious.

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