Postgres server not starting anymore
The /etc/hosts file was incorrectly configured, due to some changes to that file previously. It did not cause trouble immediately, but for some reason changing the file back to defaults (i.e., 127.0.0.1 for the local host and 127.0.1.1 for my machine) solved the problem.

This was discovered by running netstat -tulpn | grep :5432, which gave the following error output: sudo: unable to resolve host &lt;my_machine&gt;. This pointed to the fact that there was a problem with the /etc/hosts file. 

For a helpful resource, see this link.