here is /var/log/postgresql/postgresql-12-main.log 2020-07-13 18:07:02.049 UTC [1092] FATAL: could not load server certificate file "/etc/ssl/certs/ssl-cert-snakeoil.pem": No such file or directory 2020-07-13 18:07:02.050 UTC [1092] LOG: database system is shut down pg_ctl: could not start server
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What's wrong with postgresql server?
The log message you supplied seems self-explanatory...