Ubuntu Manpage: /proc/pid/mountinfo

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.

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DESCRIPTION

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