/proc/<pid>/mountinfo provides information about mounts.

This 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)

where:

• (1) mount ID: unique identifier of the mount (may be reused after umount)
• (2) parent ID: ID of parent (or of self for the top of the mount tree)
• (3) major:minor: value of st_dev for files on filesystem
• (4) root: root of the mount within the filesystem
• (5) mount point: mount point relative to the process's root
• (6) mount options: per mount options
• (7) optional fields: zero or more fields of the form “tag[:value]”
• (8) separator: marks the end of the optional fields
• (9) filesystem type: name of filesystem of the form “type[.subtype]”
• (10) mount source: filesystem specific information or “none”
• (11) super options: per super block options

Parsers should ignore all unrecognised optional fields. Currently the possible optional fields are:

• shared:X mount is shared in peer group X
• master:X mount is slave to peer group X
• propagate_from:X mount is slave and receives propagation from peer group X (*)
• unbindable mount is unbindable

where:

• (*) X is the closest dominant peer group under the process's root. If X is the immediate master of the mount, or if there's no dominant peer group under the same root, then only the “master:X” field is present and not the “propagate_from:X” field.

For more information on mount propagation see:

Documentation/filesystems/sharedsubtree.txt