proc_pid_mountinfo(5) — Linux manual page

NAME | DESCRIPTION | SEE ALSO | COLOPHON

proc_pid_mountinfo(5)      File Formats Manual     proc_pid_mountinfo(5)

NAME         top

       /proc/pid/mountinfo - mount information

DESCRIPTION         top

       /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         top

       proc(5)

COLOPHON         top

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