Which command should be used to edit the sudoers file safely to prevent issues?

The command used to edit the sudoers file safely is visudo. This command specifically opens the sudoers file in a controlled manner, providing a check for syntax errors before saving any changes. This is crucial because any syntax errors in the sudoers file can lead to loss of sudo access, potentially locking out the user from administrative functions. Visudo temporarily creates a lock on the sudoers file to prevent simultaneous editing by multiple users and ensures that the modifications made are validated before they are applied.

In contrast, using typical text editors like vi or nano does not incorporate the same safeguards. These editors could allow for unintentional errors that might not be caught until after saving, resulting in serious access issues. Chmod, which changes file permissions, is not applicable for editing the sudoers file and does not facilitate any editing process at all, making it an unsuitable choice in this context.