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

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.

Answer 2

Yes this type of error is seen by every newbie user to pgadmin.
I have found this solution and it worked for me.
sudo -u postgres psql
This will ask for your system password and then you will get the postgres prompt.
and then in psql type below command to change the password.
\password
now enter the new password and re-enter it.

Answer 3

PostGreSQL Account Debugging Steps (Linux Specific):
Make sure you actually have it installed (not just the client, the server too).
Make sure it is running.
Make sure you know where this is - usually in /var/lib/pgsql/data - however this could be anywhere - /var/lib/pgsql/unrelated-instance. Check your postgres process to see which directory (-D argument) this is.
Modify the pg_hba.conf file in the directory from the last step. I have no idea why this step isn't in the postgres documentation.
The specific configuration has been covered in e.g. Jay and Craig Ringer's answer. Make sure to configure both IPV4 and IPV6.
Restart the server.
Test that your configuration worked. Repeat 5-7 until you can login successfully.
Important Don't stop! Now you should configure a more secure password option - postgres may be fine for doing quick local setup, but you want to be using a more secure, configurable authentication mechanism, like LDAP, Kerberos, or GSSAPI. Additionally, you want to make sure you have SSL turned on.