I am running postgres 15 in linux box. Started the postgres with services and it is running successfully.

[root@server123 ~]# systemctl start postgresql.service
[root@server123 ~]# systemctl status postgresql.service
● postgresql.service - PostgreSQL database server
   Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: disabled)
  Drop-In: /etc/systemd/system/postgresql.service.d
           └─override.conf
   Active: active (running) since Fri 2024-06-14 19:26:18 IST; 29min ago
  Process: 33815 ExecStartPre=/usr/libexec/postgresql-check-db-dir postgresql (code=exited, status=0/SUCCESS)
 Main PID: 33818 (postmaster)
    Tasks: 7 (limit: 100388)
   Memory: 19.2M
   CGroup: /system.slice/postgresql.service
           ├─33818 /usr/bin/postmaster -D /pgsql_15/data
           ├─33818 /usr/bin/postmaster -D /pgsql_15/data
           ├─33821 postgres: logger
           ├─33822 postgres: checkpointer
           ├─33823 postgres: background writer
           ├─33825 postgres: walwriter
           ├─33826 postgres: autovacuum launcher
           └─33827 postgres: logical replication launcher

Also verified the postgres from ps -ef

[root@server123 ~]# ps -ef | grep postgres
postgres   33818       1  0 19:26 ?        00:00:00 /usr/bin/postmaster -D /pgsql_15/data
postgres   33821   33818  0 19:26 ?        00:00:00 postgres: logger
postgres   33822   33818  0 19:26 ?        00:00:00 postgres: checkpointer
postgres   33823   33818  0 19:26 ?        00:00:00 postgres: background writer
postgres   33825   33818  0 19:26 ?        00:00:00 postgres: walwriter
postgres   33826   33818  0 19:26 ?        00:00:00 postgres: autovacuum launcher
postgres   33827   33818  0 19:26 ?        00:00:00 postgres: logical replication launcher
root       34198   33900  0 19:58 pts/0    00:00:00 grep --color=auto postgres

owner and permission of pgsql_15/data

drwxr-x---.  4 postgres         postgres   4096 Jun 14 16:32 pgsql_15

owner and permission of /usr/bin/psql

-rwxr-xr-x 1 root root 821280 Feb  9 18:42 psql

I have put trust method for local connections

# "local" is for Unix domain socket connections only
local   all             all                                     scram-sha-256
# IPv4 local connections:
host    all             all             127.0.0.1/32            trust #scram-sha-256
# IPv6 local connections:
host    all             all             ::1/128                 trust #scram-sha-256

But when I try connect psql through postgres user it asks for password.

[root@server123 ~]# su - postgres
Last login: Fri Jun 14 19:51:31 IST 2024 on pts/0
[postgres@server123 ~]$ psql
Password for user postgres:

I want to connect to database through psql mode where without password. Where i am making wrong. please help.