Login with the Postgres user to open the logs and do other task on these paths:
The data is located here:
/postgresql/db/data
The log files are located here:
/postgresql/db/logs
Example: These are messages from one log file:
LOG: database system was shut down in recovery at 2017-08-24 16:02:55 EDT
LOG database system was not properly shut down: automatic recovery in progress
LOG: redo starts at 156/47729A80
FATAL: the database system is starting up
In this case the workaround is wait for the start up process to finish.