$ drush pm-list
Command pm-list needs a higher bootstrap level to run - you will need to invoke drush from a more functional Drupal environment to run this command. [error]
The drush command 'pm-list' could not be executed. [error]
Drush was not able to start (bootstrap) the Drupal database. [error]
Hint: This may occur when Drush is trying to:
* bootstrap a site that has not been installed or does not have a configured database. In this case you can select another site with a working database setup by specifying the URI to use with the --uri parameter on the command line. See `drush topic docs-aliases` for details.
* connect the database through a socket. The socket file may be wrong or the php-cli may have no access to it in a jailed shell. See http://drupal.org/node/1428638 for details.
The problem with this is that my current working directory was the root of a working Drupal website. Typing "drush sql-connect" sure enough gave me the correct MySQL command to connect with the database. So why the bleep was Drush failing like this.
After quite a bit of yahoogling and pondering I eventually read the Drush documentation carefully. On the configuration page there are various things said about the PHP version and configuration required to successfully run Drush. A dawning of realization grew upon me that said "your PHP is too old".
The site in question is hosted on Dreamhost. Running "php --version" told me that Drush was likely being executed by PHP 5.3. On that configuration page is special instructions for PHP 5.3. Hurm.
It also says you can do this:
$ export DRUSH_PHP='/path/to/php'
On Dreamhost VPS's other PHP versions are in /usr/local/bin with this sort of setup:
$ which php-5.4
/usr/local/bin/php-5.4
Hence ...
$ export DRUSH_PHP='/usr/local/bin/php-5.4'
And Drush magically starts working:
$ drush pm-list --core
Package Name Type Status Version
Core - optional Aggregator (aggregator) Module Not installed 6.34
Core - optional Blog (blog) Module Enabled 6.34
Core - optional Blog API (blogapi) Module Enabled 6.34
Core - optional Book (book) Module Enabled 6.34
Core - optional Color (color) Module Enabled 6.34
Core - optional Comment (comment) Module Enabled 6.34
...
That configuration page has other useful information for configuring Drush execution. Just remember to add everything to your ~/.bashrc so it's active the next time you log in.