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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-24 04:52:22 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-24 04:52:22 +0000
commit3d08cd331c1adcf0d917392f7e527b3f00511748 (patch)
tree312f0d1e1632f48862f044b8bb87e602dcffb5f9 /man2/mount.2
parentAdding debian version 6.7-2. (diff)
downloadmanpages-3d08cd331c1adcf0d917392f7e527b3f00511748.tar.xz
manpages-3d08cd331c1adcf0d917392f7e527b3f00511748.zip
Merging upstream version 6.8.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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-.\" Copyright (C) 1993 Rickard E. Faith <faith@cs.unc.edu>
-.\" and Copyright (C) 1994 Andries E. Brouwer <aeb@cwi.nl>
-.\" and Copyright (C) 2002, 2005, 2016 Michael Kerrisk <mtk.manpages@gmail.com>
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.\" Modified 1996-11-04 by Eric S. Raymond <esr@thyrsus.com>
-.\" Modified 2001-10-13 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" Added note on historical behavior of MS_NOSUID
-.\" Modified 2002-05-16 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" Extensive changes and additions
-.\" Modified 2002-05-27 by aeb
-.\" Modified 2002-06-11 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" Enhanced descriptions of MS_MOVE, MS_BIND, and MS_REMOUNT
-.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" 2005-05-18, mtk, Added MNT_EXPIRE, plus a few other tidy-ups.
-.\" 2008-10-06, mtk: move umount*() material into separate umount.2 page.
-.\" 2008-10-06, mtk: Add discussion of namespaces.
-.\"
-.TH mount 2 2023-10-31 "Linux man-pages 6.7"
-.SH NAME
-mount \- mount filesystem
-.SH LIBRARY
-Standard C library
-.RI ( libc ", " \-lc )
-.SH SYNOPSIS
-.nf
-.B "#include <sys/mount.h>"
-.P
-.BI "int mount(const char *" source ", const char *" target ,
-.BI " const char *" filesystemtype ", unsigned long " mountflags ,
-.BI " const void *_Nullable " data );
-.fi
-.SH DESCRIPTION
-.BR mount ()
-attaches the filesystem specified by
-.I source
-(which is often a pathname referring to a device,
-but can also be the pathname of a directory or file,
-or a dummy string) to the location (a directory or file)
-specified by the pathname in
-.IR target .
-.P
-Appropriate privilege (Linux: the
-.B CAP_SYS_ADMIN
-capability) is required to mount filesystems.
-.P
-Values for the
-.I filesystemtype
-argument supported by the kernel are listed in
-.I /proc/filesystems
-(e.g., "btrfs", "ext4", "jfs", "xfs", "vfat", "fuse",
-"tmpfs", "cgroup", "proc", "mqueue", "nfs", "cifs", "iso9660").
-Further types may become available when the appropriate modules
-are loaded.
-.P
-The
-.I data
-argument is interpreted by the different filesystems.
-Typically it is a string of comma-separated options
-understood by this filesystem.
-See
-.BR mount (8)
-for details of the options available for each filesystem type.
-This argument may be specified as NULL, if there are no options.
-.P
-A call to
-.BR mount ()
-performs one of a number of general types of operation,
-depending on the bits specified in
-.IR mountflags .
-The choice of which operation to perform is determined by
-testing the bits set in
-.IR mountflags ,
-with the tests being conducted in the order listed here:
-.IP \[bu] 3
-Remount an existing mount:
-.I mountflags
-includes
-.BR MS_REMOUNT .
-.IP \[bu]
-Create a bind mount:
-.I mountflags
-includes
-.BR MS_BIND .
-.IP \[bu]
-Change the propagation type of an existing mount:
-.I mountflags
-includes one of
-.BR MS_SHARED ,
-.BR MS_PRIVATE ,
-.BR MS_SLAVE ,
-or
-.BR MS_UNBINDABLE .
-.IP \[bu]
-Move an existing mount to a new location:
-.I mountflags
-includes
-.BR MS_MOVE .
-.IP \[bu]
-Create a new mount:
-.I mountflags
-includes none of the above flags.
-.P
-Each of these operations is detailed later in this page.
-Further flags may be specified in
-.I mountflags
-to modify the behavior of
-.BR mount (),
-as described below.
-.\"
-.SS Additional mount flags
-The list below describes the additional flags that can be specified in
-.IR mountflags .
-Note that some operation types ignore some or all of these flags,
-as described later in this page.
-.\"
-.\" FIXME 2.6.25 Added MS_I_VERSION, which needs to be documented.
-.\" commit 7a224228ed79d587ece2304869000aad1b8e97dd
-.\" (This is a per-superblock flag)
-.\"
-.TP
-.BR MS_DIRSYNC " (since Linux 2.5.19)"
-Make directory changes on this filesystem synchronous.
-(This property can be obtained for individual directories
-or subtrees using
-.BR chattr (1).)
-.TP
-.BR MS_LAZYTIME " (since Linux 4.0)"
-.\" commit 0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8
-.\" commit fe032c422c5ba562ba9c2d316f55e258e03259c6
-.\" commit a26f49926da938f47561f386be56a83dd37a496d
-Reduce on-disk updates of inode timestamps (atime, mtime, ctime)
-by maintaining these changes only in memory.
-The on-disk timestamps are updated only when:
-.RS
-.IP \[bu] 3
-the inode needs to be updated for some change unrelated to file timestamps;
-.IP \[bu]
-the application employs
-.BR fsync (2),
-.BR syncfs (2),
-or
-.BR sync (2);
-.IP \[bu]
-an undeleted inode is evicted from memory; or
-.IP \[bu]
-more than 24 hours have passed since the inode was written to disk.
-.RE
-.IP
-This mount option significantly reduces writes
-needed to update the inode's timestamps, especially mtime and atime.
-However, in the event of a system crash, the atime and mtime fields
-on disk might be out of date by up to 24 hours.
-.IP
-Examples of workloads where this option could be of significant benefit
-include frequent random writes to preallocated files,
-as well as cases where the
-.B MS_STRICTATIME
-mount option is also enabled.
-(The advantage of combining
-.B MS_STRICTATIME
-and
-.B MS_LAZYTIME
-is that
-.BR stat (2)
-will return the correctly updated atime, but the atime updates
-will be flushed to disk only in the cases listed above.)
-.TP
-.B MS_MANDLOCK
-Permit mandatory locking on files in this filesystem.
-(Mandatory locking must still be enabled on a per-file basis,
-as described in
-.BR fcntl (2).)
-Since Linux 4.5,
-.\" commit 95ace75414f312f9a7b93d873f386987b92a5301
-this mount option requires the
-.B CAP_SYS_ADMIN
-capability and a kernel configured with the
-.B CONFIG_MANDATORY_FILE_LOCKING
-option.
-Mandatory locking has been fully deprecated in Linux 5.15, so
-this flag should be considered deprecated.
-.TP
-.B MS_NOATIME
-Do not update access times for (all types of) files on this filesystem.
-.TP
-.B MS_NODEV
-Do not allow access to devices (special files) on this filesystem.
-.TP
-.B MS_NODIRATIME
-Do not update access times for directories on this filesystem.
-This flag provides a subset of the functionality provided by
-.BR MS_NOATIME ;
-that is,
-.B MS_NOATIME
-implies
-.BR MS_NODIRATIME .
-.TP
-.B MS_NOEXEC
-Do not allow programs to be executed from this filesystem.
-.\" (Possibly useful for a filesystem that contains non-Linux executables.
-.\" Often used as a security feature, e.g., to make sure that restricted
-.\" users cannot execute files uploaded using ftp or so.)
-.TP
-.B MS_NOSUID
-Do not honor set-user-ID and set-group-ID bits or file capabilities
-when executing programs from this filesystem.
-In addition, SELinux domain
-transitions require the permission
-.IR nosuid_transition ,
-which in turn needs
-also the policy capability
-.IR nnp_nosuid_transition .
-.\" (This is a security feature to prevent users executing set-user-ID and
-.\" set-group-ID programs from removable disk devices.)
-.TP
-.B MS_RDONLY
-Mount filesystem read-only.
-.TP
-.BR MS_REC " (since Linux 2.4.11)"
-Used in conjunction with
-.B MS_BIND
-to create a recursive bind mount,
-and in conjunction with the propagation type flags to recursively change
-the propagation type of all of the mounts in a subtree.
-See below for further details.
-.TP
-.BR MS_RELATIME " (since Linux 2.6.20)"
-When a file on this filesystem is accessed,
-update the file's last access time (atime) only if the current value
-of atime is less than or equal to the file's last modification time (mtime)
-or last status change time (ctime).
-This option is useful for programs, such as
-.BR mutt (1),
-that need to know when a file has been read since it was last modified.
-Since Linux 2.6.30, the kernel defaults to the behavior provided
-by this flag (unless
-.B MS_NOATIME
-was specified), and the
-.B MS_STRICTATIME
-flag is required to obtain traditional semantics.
-In addition, since Linux 2.6.30,
-the file's last access time is always updated if it
-is more than 1 day old.
-.\" Matthew Garrett notes in the patch that added this behavior
-.\" that this lets utilities such as tmpreaper (which deletes
-.\" files based on last access time) work correctly.
-.TP
-.BR MS_SILENT " (since Linux 2.6.17)"
-Suppress the display of certain
-.RI ( printk ())
-warning messages in the kernel log.
-This flag supersedes the misnamed and obsolete
-.B MS_VERBOSE
-flag (available since Linux 2.4.12), which has the same meaning.
-.TP
-.BR MS_STRICTATIME " (since Linux 2.6.30)"
-Always update the last access time (atime) when files on this
-filesystem are accessed.
-(This was the default behavior before Linux 2.6.30.)
-Specifying this flag overrides the effect of setting the
-.B MS_NOATIME
-and
-.B MS_RELATIME
-flags.
-.TP
-.B MS_SYNCHRONOUS
-Make writes on this filesystem synchronous (as though
-the
-.B O_SYNC
-flag to
-.BR open (2)
-was specified for all file opens to this filesystem).
-.TP
-.BR MS_NOSYMFOLLOW " (since Linux 5.10)"
-.\" dab741e0e02bd3c4f5e2e97be74b39df2523fc6e
-Do not follow symbolic links when resolving paths.
-Symbolic links can still be created,
-and
-.BR readlink (1),
-.BR readlink (2),
-.BR realpath (1),
-and
-.BR realpath (3)
-all still work properly.
-.P
-From Linux 2.4 onward, some of the above flags are
-settable on a per-mount basis,
-while others apply to the superblock of the mounted filesystem,
-meaning that all mounts of the same filesystem share those flags.
-(Previously, all of the flags were per-superblock.)
-.P
-The per-mount-point flags are as follows:
-.IP \[bu] 3
-Since Linux 2.4:
-.BR MS_NODEV ", " MS_NOEXEC ", and " MS_NOSUID
-flags are settable on a per-mount-point basis.
-.IP \[bu]
-Additionally, since Linux 2.6.16:
-.B MS_NOATIME
-and
-.BR MS_NODIRATIME .
-.IP \[bu]
-Additionally, since Linux 2.6.20:
-.BR MS_RELATIME .
-.P
-The following flags are per-superblock:
-.BR MS_DIRSYNC ,
-.BR MS_LAZYTIME ,
-.BR MS_MANDLOCK ,
-.BR MS_SILENT ,
-and
-.BR MS_SYNCHRONOUS .
-.\" And MS_I_VERSION?
-The initial settings of these flags are determined on the first
-mount of the filesystem, and will be shared by all subsequent mounts
-of the same filesystem.
-Subsequently, the settings of the flags can be changed
-via a remount operation (see below).
-Such changes will be visible via all mounts associated
-with the filesystem.
-.P
-Since Linux 2.6.16,
-.B MS_RDONLY
-can be set or cleared on a per-mount-point basis as well as on
-the underlying filesystem superblock.
-The mounted filesystem will be writable only if neither the filesystem
-nor the mountpoint are flagged as read-only.
-.\"
-.SS Remounting an existing mount
-An existing mount may be remounted by specifying
-.B MS_REMOUNT
-in
-.IR mountflags .
-This allows you to change the
-.I mountflags
-and
-.I data
-of an existing mount without having to unmount and remount the filesystem.
-.I target
-should be the same value specified in the initial
-.BR mount ()
-call.
-.P
-The
-.I source
-and
-.I filesystemtype
-arguments are ignored.
-.P
-The
-.I mountflags
-and
-.I data
-arguments should match the values used in the original
-.BR mount ()
-call, except for those parameters that are being deliberately changed.
-.P
-The following
-.I mountflags
-can be changed:
-.BR MS_LAZYTIME ,
-.\" FIXME
-.\" MS_LAZYTIME seems to be available only on a few filesystems,
-.\" and on ext4, it seems (from experiment that this flag
-.\" can only be enabled (but not disabled) on a remount.
-.\" The following code in ext4_remount() (kernel 4.17) seems to
-.\" confirm this:
-.\"
-.\" if (*flags & SB_LAZYTIME)
-.\" sb->s_flags |= SB_LAZYTIME;
-.BR MS_MANDLOCK ,
-.BR MS_NOATIME ,
-.BR MS_NODEV ,
-.BR MS_NODIRATIME ,
-.BR MS_NOEXEC ,
-.BR MS_NOSUID ,
-.BR MS_RELATIME ,
-.BR MS_RDONLY ,
-.B MS_STRICTATIME
-(whose effect is to clear the
-.B MS_NOATIME
-and
-.B MS_RELATIME
-flags),
-and
-.BR MS_SYNCHRONOUS .
-Attempts to change the setting of the
-.\" See the definition of MS_RMT_MASK in include/uapi/linux/fs.h,
-.\" which excludes MS_DIRSYNC and MS_SILENT, although SB_DIRSYNC
-.\" and SB_SILENT are split out as per-superblock flags in do_mount()
-.\" (Linux 4.17 source code)
-.B MS_DIRSYNC
-and
-.B MS_SILENT
-flags during a remount are silently ignored.
-Note that changes to per-superblock flags are visible via
-all mounts of the associated filesystem
-(because the per-superblock flags are shared by all mounts).
-.P
-Since Linux 3.17,
-.\" commit ffbc6f0ead47fa5a1dc9642b0331cb75c20a640e
-if none of
-.BR MS_NOATIME ,
-.BR MS_NODIRATIME ,
-.BR MS_RELATIME ,
-or
-.B MS_STRICTATIME
-is specified in
-.IR mountflags ,
-then the remount operation preserves the existing values of these flags
-(rather than defaulting to
-.BR MS_RELATIME ).
-.P
-Since Linux 2.6.26, the
-.B MS_REMOUNT
-flag can be used with
-.B MS_BIND
-to modify only the per-mount-point flags.
-.\" See https://lwn.net/Articles/281157/
-This is particularly useful for setting or clearing the "read-only"
-flag on a mount without changing the underlying filesystem.
-Specifying
-.I mountflags
-as:
-.P
-.in +4n
-.EX
-MS_REMOUNT | MS_BIND | MS_RDONLY
-.EE
-.in
-.P
-will make access through this mountpoint read-only, without affecting
-other mounts.
-.\"
-.SS Creating a bind mount
-If
-.I mountflags
-includes
-.B MS_BIND
-(available since Linux 2.4),
-.\" since Linux 2.4.0-test9
-then perform a bind mount.
-A bind mount makes a file or a directory subtree visible at
-another point within the single directory hierarchy.
-Bind mounts may cross filesystem boundaries and span
-.BR chroot (2)
-jails.
-.P
-The
-.I filesystemtype
-and
-.I data
-arguments are ignored.
-.P
-The remaining bits (other than
-.BR MS_REC ,
-described below) in the
-.I mountflags
-argument are also ignored.
-(The bind mount has the same mount options as
-the underlying mount.)
-However, see the discussion of remounting above,
-for a method of making an existing bind mount read-only.
-.P
-By default, when a directory is bind mounted,
-only that directory is mounted;
-if there are any submounts under the directory tree,
-they are not bind mounted.
-If the
-.B MS_REC
-flag is also specified, then a recursive bind mount operation is performed:
-all submounts under the
-.I source
-subtree (other than unbindable mounts)
-are also bind mounted at the corresponding location in the
-.I target
-subtree.
-.\"
-.SS Changing the propagation type of an existing mount
-If
-.I mountflags
-includes one of
-.BR MS_SHARED ,
-.BR MS_PRIVATE ,
-.BR MS_SLAVE ,
-or
-.B MS_UNBINDABLE
-(all available since Linux 2.6.15),
-then the propagation type of an existing mount is changed.
-If more than one of these flags is specified, an error results.
-.P
-The only other flags that can be specified while changing
-the propagation type are
-.B MS_REC
-(described below) and
-.B MS_SILENT
-(which is ignored).
-.P
-The
-.IR source ,
-.IR filesystemtype ,
-and
-.I data
-arguments are ignored.
-.P
-The meanings of the propagation type flags are as follows:
-.TP
-.B MS_SHARED
-Make this mount shared.
-Mount and unmount events immediately under this mount will propagate
-to the other mounts that are members of this mount's peer group.
-Propagation here means that the same mount or unmount will automatically
-occur under all of the other mounts in the peer group.
-Conversely, mount and unmount events that take place under
-peer mounts will propagate to this mount.
-.TP
-.B MS_PRIVATE
-Make this mount private.
-Mount and unmount events do not propagate into or out of this mount.
-.TP
-.B MS_SLAVE
-If this is a shared mount that is a member of a peer group
-that contains other members, convert it to a slave mount.
-If this is a shared mount that is a member of a peer group
-that contains no other members, convert it to a private mount.
-Otherwise, the propagation type of the mount is left unchanged.
-.IP
-When a mount is a slave,
-mount and unmount events propagate into this mount from
-the (master) shared peer group of which it was formerly a member.
-Mount and unmount events under this mount do not propagate to any peer.
-.IP
-A mount can be the slave of another peer group
-while at the same time sharing mount and unmount events
-with a peer group of which it is a member.
-.TP
-.B MS_UNBINDABLE
-Make this mount unbindable.
-This is like a private mount,
-and in addition this mount can't be bind mounted.
-When a recursive bind mount
-.RB ( mount ()
-with the
-.B MS_BIND
-and
-.B MS_REC
-flags) is performed on a directory subtree,
-any unbindable mounts within the subtree are automatically pruned
-(i.e., not replicated)
-when replicating that subtree to produce the target subtree.
-.P
-By default, changing the propagation type affects only the
-.I target
-mount.
-If the
-.B MS_REC
-flag is also specified in
-.IR mountflags ,
-then the propagation type of all mounts under
-.I target
-is also changed.
-.P
-For further details regarding mount propagation types
-(including the default propagation type assigned to new mounts), see
-.BR mount_namespaces (7).
-.\"
-.SS Moving a mount
-If
-.I mountflags
-contains the flag
-.B MS_MOVE
-(available since Linux 2.4.18),
-then move a subtree:
-.I source
-specifies an existing mount and
-.I target
-specifies the new location to which that mount is to be relocated.
-The move is atomic: at no point is the subtree unmounted.
-.P
-The remaining bits in the
-.I mountflags
-argument are ignored, as are the
-.I filesystemtype
-and
-.I data
-arguments.
-.\"
-.SS Creating a new mount
-If none of
-.BR MS_REMOUNT ,
-.BR MS_BIND ,
-.BR MS_MOVE ,
-.BR MS_SHARED ,
-.BR MS_PRIVATE ,
-.BR MS_SLAVE ,
-or
-.B MS_UNBINDABLE
-is specified in
-.IR mountflags ,
-then
-.BR mount ()
-performs its default action: creating a new mount.
-.I source
-specifies the source for the new mount, and
-.I target
-specifies the directory at which to create the mount point.
-.P
-The
-.I filesystemtype
-and
-.I data
-arguments are employed, and further bits may be specified in
-.I mountflags
-to modify the behavior of the call.
-.\"
-.SH RETURN VALUE
-On success, zero is returned.
-On error, \-1 is returned, and
-.I errno
-is set to indicate the error.
-.SH ERRORS
-The error values given below result from filesystem type independent
-errors.
-Each filesystem type may have its own special errors and its
-own special behavior.
-See the Linux kernel source code for details.
-.TP
-.B EACCES
-A component of a path was not searchable.
-(See also
-.BR path_resolution (7).)
-.TP
-.B EACCES
-Mounting a read-only filesystem was attempted without giving the
-.B MS_RDONLY
-flag.
-.IP
-The filesystem may be read-only for various reasons, including:
-it resides on a read-only optical disk;
-it is resides on a device with a physical switch that has been set to
-mark the device read-only;
-the filesystem implementation was compiled with read-only support;
-or errors were detected when initially mounting the filesystem,
-so that it was marked read-only
-and can't be remounted as read-write (until the errors are fixed).
-.IP
-Some filesystems instead return the error
-.B EROFS
-on an attempt to mount a read-only filesystem.
-.TP
-.B EACCES
-The block device
-.I source
-is located on a filesystem mounted with the
-.B MS_NODEV
-option.
-.\" mtk: Probably: write permission is required for MS_BIND, with
-.\" the error EPERM if not present; CAP_DAC_OVERRIDE is required.
-.TP
-.B EBUSY
-An attempt was made to stack a new mount directly on
-top of an existing mount point that was created in this
-mount namespace with the same
-.I source
-and
-.IR target .
-.TP
-.B EBUSY
-.I source
-cannot be remounted read-only,
-because it still holds files open for writing.
-.TP
-.B EFAULT
-One of the pointer arguments points outside the user address space.
-.TP
-.B EINVAL
-.I source
-had an invalid superblock.
-.TP
-.B EINVAL
-A remount operation
-.RB ( MS_REMOUNT )
-was attempted, but
-.I source
-was not already mounted on
-.IR target .
-.TP
-.B EINVAL
-A move operation
-.RB ( MS_MOVE )
-was attempted, but the mount tree under
-.I source
-includes unbindable mounts and
-.I target
-is a mount that has propagation type
-.BR MS_SHARED .
-.TP
-.B EINVAL
-A move operation
-.RB ( MS_MOVE )
-was attempted, but the parent mount of
-.I source
-mount has propagation type
-.BR MS_SHARED .
-.TP
-.B EINVAL
-A move operation
-.RB ( MS_MOVE )
-was attempted, but
-.I source
-was not a mount, or was \[aq]/\[aq].
-.TP
-.B EINVAL
-A bind operation
-.RB ( MS_BIND )
-was requested where
-.I source
-referred a mount namespace magic link (i.e., a
-.IR /proc/ pid /ns/mnt
-magic link or a bind mount to such a link)
-and the propagation type of the parent mount of
-.I target
-was
-.BR MS_SHARED ,
-.\" See commit 8823c079ba7136dc1948d6f6dcb5f8022bde438e
-but propagation of the requested bind mount could lead to a circular
-dependency that might prevent the mount namespace from ever being freed.
-.TP
-.B EINVAL
-.I mountflags
-includes more than one of
-.BR MS_SHARED ,
-.BR MS_PRIVATE ,
-.BR MS_SLAVE ,
-or
-.BR MS_UNBINDABLE .
-.TP
-.B EINVAL
-.I mountflags
-includes
-.BR MS_SHARED ,
-.BR MS_PRIVATE ,
-.BR MS_SLAVE ,
-or
-.B MS_UNBINDABLE
-and also includes a flag other than
-.B MS_REC
-or
-.BR MS_SILENT .
-.TP
-.B EINVAL
-An attempt was made to bind mount an unbindable mount.
-.TP
-.B EINVAL
-In an unprivileged mount namespace
-(i.e., a mount namespace owned by a user namespace
-that was created by an unprivileged user),
-a bind mount operation
-.RB ( MS_BIND )
-was attempted without specifying
-.RB ( MS_REC ),
-which would have revealed the filesystem tree underneath one of
-the submounts of the directory being bound.
-.TP
-.B ELOOP
-Too many links encountered during pathname resolution.
-.TP
-.B ELOOP
-A move operation was attempted, and
-.I target
-is a descendant of
-.IR source .
-.TP
-.B EMFILE
-(In case no block device is required:)
-Table of dummy devices is full.
-.TP
-.B ENAMETOOLONG
-A pathname was longer than
-.BR MAXPATHLEN .
-.TP
-.B ENODEV
-.I filesystemtype
-not configured in the kernel.
-.TP
-.B ENOENT
-A pathname was empty or had a nonexistent component.
-.TP
-.B ENOMEM
-The kernel could not allocate a free page to copy filenames or data into.
-.TP
-.B ENOTBLK
-.I source
-is not a block device (and a device was required).
-.TP
-.B ENOTDIR
-.IR target ,
-or a prefix of
-.IR source ,
-is not a directory.
-.TP
-.B ENXIO
-The major number of the block device
-.I source
-is out of range.
-.TP
-.B EPERM
-The caller does not have the required privileges.
-.TP
-.B EPERM
-An attempt was made to modify
-.RB ( MS_REMOUNT )
-the
-.BR MS_RDONLY ,
-.BR MS_NOSUID ,
-or
-.B MS_NOEXEC
-flag, or one of the "atime" flags
-.RB ( MS_NOATIME ,
-.BR MS_NODIRATIME ,
-.BR MS_RELATIME )
-of an existing mount, but the mount is locked; see
-.BR mount_namespaces (7).
-.TP
-.B EROFS
-Mounting a read-only filesystem was attempted without giving the
-.B MS_RDONLY
-flag.
-See
-.BR EACCES ,
-above.
-.\"
-.SH STANDARDS
-Linux.
-.SH HISTORY
-The definitions of
-.BR MS_DIRSYNC ,
-.BR MS_MOVE ,
-.BR MS_PRIVATE ,
-.BR MS_REC ,
-.BR MS_RELATIME ,
-.BR MS_SHARED ,
-.BR MS_SLAVE ,
-.BR MS_STRICTATIME ,
-and
-.B MS_UNBINDABLE
-were added to glibc headers in glibc 2.12.
-.P
-Since Linux 2.4 a single filesystem can be mounted at
-multiple mount points, and multiple mounts can be stacked
-on the same mount point.
-.\" Multiple mounts on same mount point: since Linux 2.3.99pre7.
-.P
-The
-.I mountflags
-argument may have the magic number 0xC0ED (\fBMS_MGC_VAL\fP)
-in the top 16 bits.
-(All of the other flags discussed in DESCRIPTION
-occupy the low order 16 bits of
-.IR mountflags .)
-Specifying
-.B MS_MGC_VAL
-was required before Linux 2.4,
-but since Linux 2.4 is no longer required and is ignored if specified.
-.P
-The original
-.B MS_SYNC
-flag was renamed
-.B MS_SYNCHRONOUS
-in 1.1.69
-when a different
-.B MS_SYNC
-was added to \fI<mman.h>\fP.
-.P
-Before Linux 2.4 an attempt to execute a set-user-ID or set-group-ID program
-on a filesystem mounted with
-.B MS_NOSUID
-would fail with
-.BR EPERM .
-Since Linux 2.4 the set-user-ID and set-group-ID bits are
-just silently ignored in this case.
-.\" The change is in patch-2.4.0-prerelease.
-.\"
-.SH NOTES
-.SS Mount namespaces
-Starting with Linux 2.4.19, Linux provides mount namespaces.
-A mount namespace is the set of filesystem mounts that
-are visible to a process.
-Mount namespaces can be (and usually are)
-shared between multiple processes,
-and changes to the namespace (i.e., mounts and unmounts) by one process
-are visible to all other processes sharing the same namespace.
-(The pre-2.4.19 Linux situation can be considered as one in which
-a single namespace was shared by every process on the system.)
-.P
-A child process created by
-.BR fork (2)
-shares its parent's mount namespace;
-the mount namespace is preserved across an
-.BR execve (2).
-.P
-A process can obtain a private mount namespace if:
-it was created using the
-.BR clone (2)
-.B CLONE_NEWNS
-flag,
-in which case its new namespace is initialized to be a
-.I copy
-of the namespace of the process that called
-.BR clone (2);
-or it calls
-.BR unshare (2)
-with the
-.B CLONE_NEWNS
-flag,
-which causes the caller's mount namespace to obtain a private copy
-of the namespace that it was previously sharing with other processes,
-so that future mounts and unmounts by the caller are invisible
-to other processes (except child processes that the caller
-subsequently creates) and vice versa.
-.P
-For further details on mount namespaces, see
-.BR mount_namespaces (7).
-.\"
-.SS Parental relationship between mounts
-Each mount has a parent mount.
-The overall parental relationship of all mounts defines
-the single directory hierarchy seen by the processes within a mount namespace.
-.P
-The parent of a new mount is defined when the mount is created.
-In the usual case,
-the parent of a new mount is the mount of the filesystem
-containing the directory or file at which the new mount is attached.
-In the case where a new mount is stacked on top of an existing mount,
-the parent of the new mount is the previous mount that was stacked
-at that location.
-.P
-The parental relationship between mounts can be discovered via the
-.IR /proc/ pid /mountinfo
-file (see below).
-.\"
-.SS \fI/proc/\fPpid\fI/mounts\fP and \fI/proc/\fPpid\fI/mountinfo\fP
-The Linux-specific
-.IR /proc/ pid /mounts
-file exposes the list of mounts in the mount
-namespace of the process with the specified ID.
-The
-.IR /proc/ pid /mountinfo
-file exposes even more information about mounts,
-including the propagation type and mount ID information that makes it
-possible to discover the parental relationship between mounts.
-See
-.BR proc (5)
-and
-.BR mount_namespaces (7)
-for details of this file.
-.SH SEE ALSO
-.BR mountpoint (1),
-.BR chroot (2),
-.BR ioctl_iflags (2),
-.BR mount_setattr (2),
-.BR pivot_root (2),
-.BR umount (2),
-.BR mount_namespaces (7),
-.BR path_resolution (7),
-.BR findmnt (8),
-.BR lsblk (8),
-.BR mount (8),
-.BR umount (8)