Which parameter should be added to the GRUB2 command to boot a Linux system in single-user mode?

To boot a Linux system in single-user mode using GRUB2, the parameter that should be added is 'single'. This instruction tells the kernel to start in single-user mode, which is a state where only the root user has access to the system and is typically used for maintenance or recovery tasks. In this mode, the system does not start all the standard services and runs a minimal environment, allowing for troubleshooting and repairs without interference from other users or processes.

While other options may seem relevant, they do not correctly invoke the single-user mode. For instance, '1' could be interpreted to indicate runlevel 1, which corresponds to a similar state in SysV init systems, but GRUB2 uses 'single' as the direct and proper keyword. The term 'single-user' is not recognized as a boot parameter in this context, and 'emergency' relates to a different, more restricted mode which is not specifically the same as single-user mode, often used for emergencies where the least amount of services are started. Thus, 'single' is the precise command needed for entering single-user mode through GRUB2.