Set auto increment primary key in PostgreSQL

set id as increment primary key:

CREATE TABLE terminal_products_backup AS TABLE terminal_products;
create sequence id_seq;
alter table terminal_products_backup alter id set default nextval('id_seq');
Select setval('id_seq', mx.mx ) FROM (SELECT MAX(id) AS mx FROM terminal_products_backup) mx;

add  increment primary key  id into table named test1

 ALTER TABLE test1 ADD COLUMN id SERIAL PRIMARY KEY;