Environment variable $PGUSER does NOT take effect with Postgresql client?

For many years I have used to use the environment variable $PGUSER when I work with client tools such as psql/pg_dump/pg_restore. Recently I build up a new PG13 server, the env var $PGUSER does **NOT** take effect, when I try to use the client tools on a terminal of the server. I get message like this: > leon@mamba:~$ echo $PGUSER > > postgres > > leon@mamba:~$ psql > > psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: > > FATAL: role "leon" does not exist If I use the tools on a terminal of another physical computer, the env var takes effect normally. Of course, the var has been set on both machines. My pg_hba.conf: > \# TYPE DATABASE USER ADDRESS METHOD > > host all all 127.0.0.1/32 trust > > host all all 192.168.x.x/16 md5 > > \# IPv6 local connections: > > host all all ::1/128 trust