man > proc_pid_mountinfo(5)

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 previ‐
                   ous 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  di‐
                   rectory.

              (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 un‐
              bindable.  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/sharedsub‐
              tree.rst (or Documentation/filesystems/sharedsubtree.txt  before  Linux  5.8)  in  the
              Linux kernel source tree.

SEE ALSO
       proc(5)

Linux man-pages 6.7                          2023-11-24                        proc_pid_mountinfo(5)