newroot

Newroot is a term used in Unix-like operating systems to describe the transition from an initial temporary root filesystem to the system’s final root filesystem. The new root is the filesystem that will be mounted as the process’s / and will host the normal init sequence, services, and user data. The concept is most visible during boot and recovery, when systems start from a minimal environment such as an initramfs or initrd before the real disk-based root can be mounted.

In Linux, the typical scenario involves booting with a small, in-memory root and an init process that prepares the real root filesystem. The initramfs collects drivers, mounts the actual root from disk or network, and then transfers control to that root so the system can continue booting normally. This transition is the moment of switching to the new root.

The transition is accomplished by specialized operations such as pivot_root or switch_root. Pivot_root changes the process’s root directory and relocates the old root somewhere under the new one, while switch_root is a helper commonly used by initramfs tools to swap the active root and execute the real init on the new filesystem. The exact mechanism depends on the boot environment and init system in use.

Newroot is also relevant in recovery scenarios and certain live-boot or container workflows, where a system must boot into an alternate filesystem or environment. Misconfiguration of the newroot process can prevent a system from booting, so careful setup and validation are important.

See also: pivot_root, switch_root, initramfs, initrd, chroot.