proc_pid_mountinfo(5)         File Formats Manual        proc_pid_mountinfo(5)

NAME
       /proc/pid/mountinfo - mount information

DESCRIPTION
       /proc/pid/mountinfo (since Linux 2.6.26)
              This file contains information about mounts in the process's
              mount namespace (see mount_namespaces(7)).  It supplies various
              information (e.g., propagation state, root of mount for bind
              mounts, identifier for each mount and its parent) that is
              missing from the (older) /proc/pid/mounts file, and fixes
              various other problems with that file (e.g., nonextensibility,
              failure to distinguish per-mount versus per-superblock options).

              The file contains lines of the form:

              36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
              (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The numbers in parentheses are labels for the descriptions
              below:

              (1)  mount ID: a unique ID for the mount (may be reused after
                   umount(2)).

              (2)  parent ID: the ID of the parent mount (or of self for the
                   root of this mount namespace's mount tree).

                   If a new mount is stacked on top of a previous existing
                   mount (so that it hides the existing mount) at pathname P,
                   then the parent of the new mount is the previous mount at
                   that location.  Thus, when looking at all the mounts
                   stacked at a particular location, the top-most mount is the
                   one that is not the parent of any other mount at the same
                   location.  (Note, however, that this top-most mount will be
                   accessible only if the longest path subprefix of P that is
                   a mount point is not itself hidden by a stacked mount.)

                   If the parent mount lies outside the process's root
                   directory (see chroot(2)), the ID shown here won't have a
                   corresponding record in mountinfo whose mount ID (field 1)
                   matches this parent mount ID (because mounts that lie
                   outside the process's root directory are not shown in
                   mountinfo).  As a special case of this point, the process's
                   root mount may have a parent mount (for the initramfs
                   filesystem) that lies outside the process's root directory,
                   and an entry for that mount will not appear in mountinfo.

              (3)  major:minor: the value of st_dev for files on this
                   filesystem (see stat(2)).

              (4)  root: the pathname of the directory in the filesystem which
                   forms the root of this mount.

              (5)  mount point: the pathname of the mount point relative to
                   the process's root directory.

              (6)  mount options: per-mount options (see mount(2)).

              (7)  optional fields: zero or more fields of the form
                   "tag[:value]"; see below.

              (8)  separator: the end of the optional fields is marked by a
                   single hyphen.

              (9)  filesystem type: the filesystem type in the form
                   "type[.subtype]".

              (10) mount source: filesystem-specific information or "none".

              (11) super options: per-superblock options (see mount(2)).

              Currently, the possible optional fields are shared, master,
              propagate_from, and unbindable.  See mount_namespaces(7) for a
              description of these fields.  Parsers should ignore all
              unrecognized optional fields.

              For more information on mount propagation see
              Documentation/filesystems/sharedsubtree.rst (or
              Documentation/filesystems/sharedsubtree.txt before Linux 5.8) in
              the Linux kernel source tree.

SEE ALSO
       proc(5)

Linux man-pages 6.9.1             2024-05-02             proc_pid_mountinfo(5)