In a Linux environment, what command and set of options would you use to recursively change the ownership of a directory and all its contents to a new user and group?

To recursively change the ownership of a directory and all its contents to a new user and group in a Linux environment, you would use the `chown` command along with the `-R` (or `--recursive`) option. The `chown` command is used to change the owner and group of files and directories. The `-R` option makes the command operate recursively, meaning it will apply the change not only to the specified directory itself but also to all files and subdirectories within it. The syntax for the command is: `chown -R newuser:newgroup directoryname`. Here, `newuser` is the username of the new owner, `newgroup` is the group name of the new group owner, and `directoryname` is the path to the directory you want to change. For example, if you wanted to change the ownership of a directory named 'project' and all its contents to a user named 'john' and a group named 'developers', you would use the command: `sudo chown -R john:developers project`. The `sudo` command is typically required because changing ownership often requires administrative privileges. Without `sudo`, you might encounter a 'Operation not permitted' error. It's important to ensure that both the user and group exist on the system before running the command. If the user or group does not exist, the `chown` command may fail or produce unexpected results.