$ locate pg_hba.conf
/usr/pgsql-9.5/share/pg_hba.conf.sample
/var/lib/pgsql/9.5/data/pg_hba.conf

$ find / -name "pg_hba.conf" 2>%1 | grep -v "Permission denied"
/var/lib/pgsql/9.5/data/pg_hba.conf

#cp /var/lib/pgsql/9.5/data/pg_hba.conf /var/lib/pgsql/9.5/data/pg_hba.conf.20210125

# TYPE DATABASE USER ADDRESS  METHOD
 
# "local" is for Unix domain socket connections only
local all all   md5
# IPv4 local connections:
host all all 127.0.0.1/32 md5
# IPv6 local connections:
host all all ::1/128  md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local replication postgres  peer
#host replication postgres 127.0.0.1/32 ident
#host replication postgres ::1/128  ident
 
# Allow access from all host to connect to this UAT server
host all all 0.0.0.0/0 md5

修改前
# "local" is for Unix domain socket connections only
local all all   md5
 
修改后
# "local" is for Unix domain socket connections only
local all all   trust

修改前：
# IPv4 local connections:
host all all 127.0.0.1/32 md5
 
 
修改后：
# IPv4 local connections:
host all all 127.0.0.1/32 trust

# service postgresql-9.5 stop
Redirecting to /bin/systemctl stop postgresql-9.5.service
# service postgresql-9.5 start
Redirecting to /bin/systemctl start postgresql-9.5.service
# service postgresql-9.5 status
Redirecting to /bin/systemctl status postgresql-9.5.service

alter user postgres with password '新的密码';

#psql -U postgres

#psql

-bash-4.2$ psql
psql (9.5.6)
Type "help" for help.
 
postgres=# alter user postgres with password 'xxxxxxxx';
ALTER ROLE