PostgreSQL

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Using psql

Depending on the system.stateVersion of your system, the default super-user username will change:

  • 17.03 and earlier: the superuser is root
  • 17.09 and later: the superuser is postgres

There is no password, Ident Authentication is used. This means that you can access the database using a system user named like the database user.

Example for a 17.03 stateVersion:

 $ sudo -u root psql
psql: FATAL:  database "root" does not exist
 $ sudo -u root psql -l
                              List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges
-----------+-------+----------+-------------+-------------+-------------------
 postgres  | root  | UTF8     | en_CA.UTF-8 | en_CA.UTF-8 |
 template0 | root  | UTF8     | en_CA.UTF-8 | en_CA.UTF-8 | =c/root          +
           |       |          |             |             | root=CTc/root
 template1 | root  | UTF8     | en_CA.UTF-8 | en_CA.UTF-8 | =c/root          +
           |       |          |             |             | root=CTc/root
(4 rows)

The first error is not an error with the credentials, but an error coming from the default behaviour of psql that is trying to use a database name named like the user logging-in. The second command lists tables available.

Examples for a 17.09 stateVersion and later:

 $ psql -U postgres

and

 $ psql -U postgres -l

Deploying databases

This example shows how to roll out a database with a default user and password:

  services.postgresql = {
    enable = true;
    package = pkgs.postgresql_10;
    enableTCPIP = true;
    authentication = pkgs.lib.mkOverride 10 ''
      local all all trust
      host all all ::1/128 trust
    '';
    initialScript = pkgs.writeText "backend-initScript" ''
      CREATE ROLE nixcloud WITH LOGIN PASSWORD 'nixcloud' CREATEDB;
      CREATE DATABASE nixcloud;
      GRANT ALL PRIVILEGES ON DATABASE nixcloud TO nixcloud;
    '';
  };

To debug the SQL statements futher, one can use systemctl cat postgresql and see the ExecStartPost=/nix/store/rnv1v95bbf2lsy9ncwg7jdwj2s71sqra-unit-script/bin/postgresql-post-start line. Then open it with `cat` on the shell and see the psql command.


Then execute the complete statement on the shell, as:

/nix/store/3mqha1naji34i6iv78i90hc20dx0hld9-sudo-1.8.20p2/bin/sudo -u postgres psql -f "/nix/store/az5nglyw7j94blxwkn2rmpi2p6z9fbmy-backend-initScript" --port=5432 -d postgres
psql:/nix/store/az5nglyw7j94blxwkn2rmpi2p6z9fbmy-backend-initScript:1: ERROR:  syntax error at or near "-"
LINE 1: CREATE ROLE nixcloud-admin WITH LOGIN PASSWORD 'nixcloud' CR...
                            ^
psql:/nix/store/az5nglyw7j94blxwkn2rmpi2p6z9fbmy-backend-initScript:2: ERROR:  database "nixcloud-db1" already exists
psql:/nix/store/az5nglyw7j94blxwkn2rmpi2p6z9fbmy-backend-initScript:3: ERROR:  syntax error at or near "-"
LINE 1: ...ALL PRIVILEGES ON DATABASE "nixcloud-db1" TO nixcloud-admin;
                                                                ^