chroot

chroot runs a command with a different directory as its root — its /. Inside that command, the chosen directory is the top of the file system, and nothing above it can be named or reached.

chroot newroot [command [arg]...]

$ chroot /mnt/system /bin/sh

With a command, chroot changes the root to newroot and runs the command there. With no command, it starts an interactive shell.

What it does #

A process normally sees the whole file system, rooted at the real /. After chroot, the named directory becomes that process's /: a path like /etc/config inside the command resolves to newroot/etc/config, and there is no path that reaches outside newroot at all.

It is used to work inside another installed system — repairing or configuring a system image by entering it — and to run a command confined to a known subtree.

For the command to be usable, newroot must already contain what the command needs: the command's own executable, and whatever libraries and files it depends on, all present under newroot.

Options #

A privileged operation #

Changing a process's root directory is a privileged operation. chroot succeeds only for a caller whose token carries the right to do it, and is refused otherwise — the ability to redraw a process's view of the file system is not something every principal holds. See Privileges.

Exit status #

chroot exits with the command's own status once it finishes. Otherwise: