ischroot

ischroot [OPTIONS]

--help
    Display a help message and exit.

--version
    Display version information and exit.

ischroot is a simple utility that determines whether the current process is operating within a chroot environment. It does this by comparing the device ID of the root directory (/) with the device ID of its parent directory (/.., which would resolve to the true root before the chroot). If these device IDs are different, it implies that the process's root directory has been changed from the true system root, indicating a chroot. The command exits with a status code of 0 if it detects a chroot, and 1 otherwise. It's commonly used in scripts to adapt behavior based on the execution environment.

ischroot is not a 100% reliable method for detecting chroot environments. It can be fooled by certain scenarios, such as nested chroots, or if the true root directory (/) and the chrooted root directory are on the same filesystem device. It primarily checks if the root filesystem has changed device ID. If the chroot is performed within the same filesystem device, it might not be detected. The detection mechanism relies on comparing the device ID of . and .. from the root directory, which can be misleading under complex mounting schemes (e.g., bind mounts).

The ischroot command provides the following exit status codes:
0: The process is running in a chroot environment.
1: The process is not running in a chroot environment.
>1: An error occurred (e.g., incorrect usage or system error).

ischroot is part of the util-linux project, a collection of essential Linux utilities. It has been a standard tool for system administrators and script developers for a significant period, providing a quick way to verify the chroot status, especially in automated build or maintenance scripts where operating inside a chroot is a critical condition. Its functionality has remained largely stable over time, emphasizing its role as a fundamental system utility.

chroot(1), chroot(2), stat(2), mount(8)