mount-namespace · shipping · also Linux mount namespace

Mount namespace

A Linux mount namespace gives its member processes a particular view of the mount hierarchy.

Related Observatory article: Mount namespace on hesela.com

Creating a namespace with CLONE_NEWNS copies the existing mount list, not the underlying file contents. Processes in different namespaces can therefore still reach the same filesystem data. [1] [2]

Propagation is a separate property of each mount. Shared mounts propagate mount and unmount events immediately beneath them among peers, potentially across namespaces; private mounts do not propagate those events. A separate namespace alone does not establish a private tree or a storage snapshot. [2]

/proc/PID/mountinfo describes the target process's mount namespace, including mount roots, propagation fields and separate per-mount and per-superblock options. Inspecting the observer's own list can miss the target's view. [3]

Command defaults differ from the system call. The util-linux unshare command makes propagation recursively private for a new mount namespace by default (since 2.27). --propagation unchanged disables that extra step. Record the entry point and options when interpreting namespace isolation. [4]

Relations

related

Bind mount, Read-only mount, Mount propagation

Citations

1. Linux man-pages: mount_namespaces(7), namespace creation and mount-list scope (accessed 2026-11-04)
2. Linux kernel documentation: Shared Subtrees, propagation and namespace copies (accessed 2026-11-04)
3. Linux man-pages: proc_pid_mountinfo(5), per-process view and option layers (accessed 2026-11-04)
4. util-linux v2.41.1: unshare(1), mount namespace defaults and propagation option (accessed 2026-11-04)

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