pgadmin3: FATAL: Ident authentification failed for user "postgres"

Question

I'm trying to register new server in pgadmin3 with following settings:

Name: postgres
Host: localhost
Username: postgres
Password: <password which works for psql>
Service: empty or postgres

But it shows error:

FATAL: Ident authentification failed for user "postgres"

I've restarted postgresql service, but to no avail.

Contents of /var/lib/pgsql/data/pg_hba.conf:

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD

# "local" is for Unix domain socket connections only
local   all         all                               trust
# IPv4 local connections:
host    all         all         127.0.0.1/32          trust
# IPv6 local connections:
host    all         all         ::1/128               ident

EDIT: Tools -> Server Configuration -> pg_hba.conf is greyed out.

Answer 1

It looks like PgAdmin-III is probably connecting over IPv6 by default, so it's using the ident line that matches the IPv6 address for localhost, ::1/128.

If you want to use password authentication, you probably want:

# IPv4 local connections:
host    all         all         127.0.0.1/32          md5
# IPv6 local connections:
host    all         all         ::1/128               md5

I'm not sure why you have the unix domain socket line set to trust, but that's probably OK if it's just a development machine, so leave it unchanged. It's really much safer to have it as ident (if you want the unix user to have to be the same as the Pg user) or md5 (for password auth on local unix sockets) though.

You'll need to edit pg_hba.conf directly in a text editor if PgAdmin-III doesn't have permissions to edit it. You could run PgAdmin-III as user postgres via sudo, but it's way safer (and probably easier) to just use nano or a similar command-line text editor to modify pg_hba.conf.

The password works for psql because psql will, unless told otherwise, connect over a unix domain socket, and you have that set to trust. You'll probably find you could give any password to psql and it'll still work, because it's never being asked to actually give the password, it's just being automatically trusted.