Доступ к оболочке PostgreSQL с помощью psql:

devir@devir:~$ docker exec -it agis-postgis-db psql -U postgres
psql (11.2 (Debian 11.2-1.pgdg90+1))
Type "help" for help.
postgres=#

devir@devir:~$ docker exec -it agis-postgis-db bash
root@48a363a8ebc2:/# su - postgres
postgres@48a363a8ebc2:~$ psql
psql (11.2 (Debian 11.2-1.pgdg90+1))
Type "help" for help.

postgres=#

Проверка версии c хоста

devir@devir:~$ docker exec -it agis-postgis-db postgres --version
postgres (PostgreSQL) 11.2 (Debian 11.2-1.pgdg90+1)

Проверка версии c контейнера

postgres=# SELECT version();
version
----------------------------------------------------------------------------------------------------------------------------------
PostgreSQL 11.2 (Debian 11.2-1.pgdg90+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit
(1 row)