ischroot

ischroot [OPTION]…

--help
    Display usage summary and exit

--version
    Output version information and exit

ischroot is a simple utility that checks if the current system is operating within a chroot(2) jail. It achieves this by inspecting the /proc filesystem, specifically comparing the target of the symlink /proc/1/root (the root directory of the init process, PID 1) to /. If they differ, it indicates a chroot environment, and the command exits with status 0 (success). Otherwise, it exits with status 1.

This tool is invaluable in scripting scenarios, such as customizing behavior during package builds or installations inside chroots created by tools like debootstrap or schroot. For example, it allows conditional execution of commands only outside the chroot, preventing issues like attempting to start services within a jailed environment.

ischroot is lightweight, with no runtime dependencies beyond a mounted /proc filesystem and a Linux kernel supporting it. It is commonly found in Debian-based distributions as part of the schroot package.

ischroot specifically detects classic chroot(2) but may fail or give false results in namespace-based containers like Docker or LXC, which often combine namespaces with bind mounts rather than pure chroot.
Requires /proc to be mounted; fails otherwise.

0: Chrooted.
1: Not chrooted.
2: Error (e.g., /proc unavailable).

Reads readlink /proc/1/root and compares to /; portable across most Linux systems with /proc.

Developed for the schroot project around 2004-2005 in Debian to aid chroot session management. Integrated into schroot 1.0 and later versions, becoming a standard tool for chroot-aware scripting.

chroot(1), schroot(1), debootstrap(8)