PostgreSQL 12 High Availability Cookbook - Third Edition

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If you have another test server with PostgreSQL installed and running, try some of these tests to confirm it works as described:

1. Start PostgreSQL and confirm the exit status is 0 for success with this command:

sudo systemctl start postgresql@12-main
echo $?

2. Stop PostgreSQL and confirm the exit status is 0 for success with this command:

sudo systemctl stop postgresql@12-main
echo $?

3. Finally, check the status of PostgreSQL while it is stopped and confirm the exit value is 3, indicating the service isn't running, with this command:

sudo systemctl status postgresql@12-main
echo $?

The $? variable represents the exit status of the previous command. It's an easy way to visualize the exit code, which is normally only used by ...