ischroot

ischroot

The ischroot command is a simple utility designed to determine whether the current process is running inside a chroot jail or container environment. It provides a reliable way for scripts and programs to adapt their behavior based on the environment they're operating in.

The primary mechanism for detection relies on comparing the device and inode numbers of the root directory (/) across different namespaces, including the root mount namespace and the process's current mount namespace. If the root directory's device and inode are different from the initial root, it strongly suggests the process is running within a chroot. Because chroots can vary widely in their implementation, relying on these identifiers offers an effective test. It can be used in scripts to conditionally execute operations that might be insecure or undesirable in a chrooted environment, for example writing to the true system root. ischroot helps automate these environment checks, improving the robustness and security of software.

ischroot relies on comparing device and inode numbers. While effective, it's not foolproof. Sophisticated methods could potentially bypass this detection. Also, the behaviour can change based on kernel level settings.

ischroot returns 0 if the process is determined to be running within a chroot jail. It returns 1 if it is not in a chroot. Any other errors produce a return code of 2 or greater.

In a shell script:
if ischroot; then echo "Running in chroot."; else echo "Not running in chroot."; fi
This conditional statement executes different code blocks based on whether the script is running in a chrooted environment.

chroot(8), unshare(1)