Which command allows a user to change the root directory for a process?

The command that allows a user to change the root directory for a process is "chroot." This command creates a new root directory for the process and its children, effectively isolating them from the rest of the filesystem. When "chroot" is executed, it changes the apparent root directory for the running process and any processes that it may start, limiting their access to files and directories outside the specified new root.

This capability is often used for testing, software development, and creating secure environments (such as jails in some systems) where a process only needs to see a limited part of the filesystem. By restricting access, the command enhances security and allows for clean environments for applications that require specific libraries or files without interfering with the system's global filesystem.

The other options listed do not represent valid Linux commands. "rootchange" and "dirchange" are not standard commands available in Linux, and "switchroot" is a command more closely associated with the Linux boot process, specifically used during system initialization rather than for changing root directories of running processes.