You can install the Delete All module which provides some command line Drush commands to remove all content and users safely.
This module is used to delete all content and/or users from a site.
This is mainly a developer tool, which can come in handy in several
cases, listed below.
The usual way to do this is to go to Administer -> Content then select
all the nodes and delete them. This works if you have a handful of
nodes only. If you have hundreds or thousands of nodes, then it is not
a practical solution.
Another option is to directly delete the nodes from the node table in
the database. This does not work properly, since there are also
comments, and many tables for add on modules that needs to be cleaned.
- This is a test site that the client was using for a period of time,
and they must clean it up before starting with real data.
- You are
testing something that creates a lot of nodes (e.g. aggregator), and
want to do it over and over again.
- You created a site in the past and
want to replicate it again, but with new content.
Note that for nodes,
comments and all additions to nodes that contributed modules may have
added. For users, any additional module data will also be deleted.