.\" 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 Michael Kerrisk <mtk.manpages@gmail.com>
+.\" and Copyright (C) 2002, 2005, 2016 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" 2008-10-06, mtk: move umount*() material into separate umount.2 page.
.\" 2008-10-06, mtk: Add discussion of namespaces.
.\"
-.TH MOUNT 2 2012-07-05 "Linux" "Linux Programmer's Manual"
+.TH MOUNT 2 2017-07-13 "Linux" "Linux Programmer's Manual"
.SH NAME
-mount \- mount file system
+mount \- mount filesystem
.SH SYNOPSIS
.nf
.B "#include <sys/mount.h>"
.fi
.SH DESCRIPTION
.BR mount ()
-attaches the file system specified by
+attaches the filesystem specified by
.I source
-(which is often a device name, but can also be a directory name
-or a dummy) to the directory specified by
+(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 .
-
+.PP
Appropriate privilege (Linux: the
.B CAP_SYS_ADMIN
-capability) is required to mount file systems.
-
-Since Linux 2.4 a single file system can be visible at
-multiple mount points, and multiple mounts can be stacked
-on the same mount point.
-.\" Multiple mounts on same mount point: since 2.3.99pre7.
-
+capability) is required to mount filesystems.
+.PP
Values for the
.I filesystemtype
argument supported by the kernel are listed in
.I /proc/filesystems
-(e.g., "minix", "ext2", "ext3", "jfs", "xfs", "reiserfs",
-"msdos", "proc", "nfs", "iso9660").
+(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.
-
+.PP
The
-.I mountflags
-argument may have the magic number 0xC0ED (\fBMS_MGC_VAL\fP)
-in the top 16 bits (this was required in kernel versions prior to 2.4, but
-is no longer required and ignored if specified),
-and various mount flags
-.\" (as defined in \fI<linux/fs.h>\fP for libc4 and libc5
-.\" and in \fI<sys/mount.h>\fP for glibc2)
-in the low order 16 bits:
-.\" FIXME 2.6.15 added flags for "shared subtree" functionality:
-.\" MS_UNBINDABLE, MS_PRIVATE, MS_SHARED, MS_SLAVE
-.\"
-.\" MS_PRIVATE.
-.\" All mounts are private by default. Previously shared mouns
-.\" can be remarked PRIVATE.
-.\" MS_SHARED
-.\" Mount points that are marked SHARED propagate mount events
-.\" to one another after bing cloned.
-.\" MS_SLAVE
-.\" A previously shared mount point can be marked SALVE, meaning
-.\" it receives propagated events, but does not propagate events.
-.\" MS_UNBINDABLE
-.\" mounts cannot be bound into other places, and will not be
-.\" propagated into new subtrees
-.\" mount --make-rshared ==> MS_SHARED | MS_REC
-.\"
-.\" These settings are visible in proc/mountinfo
-.\"
-.\"
-.\" These need to be documented on this page.
-.\" See:
-.\" Documentation/filesystems/sharedsubtree.txt
-.\"
-.\" http://lwn.net/Articles/159077/
-.\"
-.\" http://myweb.sudhaa.com:2022/~ram/sharedsubtree/paper/sharedsubtree.1.pdf
-.\" Shared-Subtree Concept, Implementation, and Applications in Linux
-.\" Al Viro viro@ftp.linux.org.uk
-.\" Ram Pai linuxram@us.ibm.com
-.\"
-.\" http://foss.in/2005/slides/sharedsubtree1.pdf
-.\" Shared Subtree Concept and Implementation in the Linux Kernel
-.\" Ram Pai
-.\"
-.\" http://www.ibm.com/developerworks/linux/library/l-mount-namespaces/index.html
-.\" Applying mount namespaces
+.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.
+.PP
+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 * 3
+Remount an existing mount:
+.IR mountflags
+includes
+.BR MS_REMOUNT .
+.IP *
+Create a bind mount:
+.IR mountflags
+includes
+.BR MS_BIND .
+.IP *
+Change the propagation type of an existing mount:
+.IR mountflags
+includes one of
+.BR MS_SHARED ,
+.BR MS_PRIVATE ,
+.BR MS_SLAVE ,
+or
+.BR MS_UNBINDABLE .
+.IP *
+Move an existing mount to a new location:
+.IR mountflags
+includes
+.BR MS_MOVE .
+.IP *
+Create a new mount:
+.IR mountflags
+includes none of the above flags.
+.PP
+Each of these operations is detailed later in this page.
+Further flags may be specified in
+.IR mountflags
+to modify the behavior of
+.BR mount (),
+as described below.
.\"
-.\" Uncover practical applications for advanced Linux mounts features
-.\" Serge E. Hallyn (sergeh@us.ibm.com), Software Engineer, IBM　
-.\" Ram Pai (linuxram@us.ibm.com), Software Engineer, IBM
-.\" Date: 17 Sep 2007
+.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.
.\"
-.\" 2.6.25 Added MS_I_VERSION, which needs to be documented.
+.\" FIXME 2.6.25 Added MS_I_VERSION, which needs to be documented.
.\"
.TP
-.BR MS_BIND " (Linux 2.4 onward)"
-.\" since 2.4.0-test9
-Perform a bind mount, making a file or a directory subtree visible at
-another point within a file system.
-Bind mounts may cross file system boundaries and span
-.BR chroot (2)
-jails.
-The
-.IR filesystemtype
-and
-.IR data
-arguments are ignored.
-Up until Linux 2.6.26,
-.I mountflags
-was also ignored
-.\" with the exception of the "hidden" MS_REC mountflags bit
-(the bind mount has the same mount options as
-the underlying mount point).
-.TP
.BR MS_DIRSYNC " (since Linux 2.5.19)"
-Make directory changes on this file system synchronous.
+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 (a) 5
+the inode needs to be updated for some change unrelated to file timestamps;
+.IP (b)
+the application employs
+.BR fsync (2),
+.BR syncfs (2),
+or
+.BR sync (2);
+.IP (c)
+an undeleted inode is evicted from memory; or
+.IP (d)
+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.
+.PP
+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
+.BR MS_STRICTATIME
+and
+.BR 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 file system.
+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).)
-.\" FIXME Say more about MS_MOVE
-.TP
-.B MS_MOVE
-Move a subtree.
-.I source
-specifies an existing mount point and
-.I target
-specifies the new location.
-The move is atomic: at no point is the subtree unmounted.
-The
-.IR filesystemtype ", " mountflags ", and " data
-arguments are ignored.
+Since Linux 4.5,
+.\" commit 95ace75414f312f9a7b93d873f386987b92a5301
+this mount option requires the
+.B CAP_SYS_ADMIN
+capability.
.TP
.B MS_NOATIME
-Do not update access times for (all types of) files on this file system.
+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 file system.
+Do not allow access to devices (special files) on this filesystem.
.TP
.B MS_NODIRATIME
-Do not update access times for directories on this file system.
+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,
.BR MS_NODIRATIME .
.TP
.B MS_NOEXEC
-Do not allow programs to be executed from this file system.
-.\" (Possibly useful for a file system that contains non-Linux executables.
+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 when executing
-programs from this file system.
+Do not honor set-user-ID and set-group-ID bits or file capabilities
+when executing programs from this filesystem.
.\" (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 file system read-only.
-.\"
-.\" FIXME Document MS_REC, available since 2.4.11.
-.\" This flag has meaning in conjunction with MS_BIND and
-.\" also with the shared subtree flags.
+Mount filesystem read-only.
.TP
-.BR MS_RELATIME " (Since Linux 2.6.20)"
-When a file on this file system is accessed,
+.BR MS_REC " (since Linux 2.4.11)"
+Used in conjunction with
+.BR 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).
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 acces time) work correctly.
-.TP
-.B MS_REMOUNT
-Remount an existing mount.
-This allows you to change the
-.I mountflags
-and
-.I data
-of an existing mount without having to unmount and remount the file system.
-.I target
-should be the same value specified in the initial
-.BR mount ()
-call;
-.I source
-and
-.I filesystemtype
-are ignored.
-
-The following
-.I mountflags
-can be changed:
-.BR MS_RDONLY ,
-.BR MS_SYNCHRONOUS ,
-.BR MS_MANDLOCK ;
-before kernel 2.6.16, the following could also be changed:
-.B MS_NOATIME
-and
-.BR MS_NODIRATIME ;
-and, additionally, before kernel 2.4.10, the following could also be changed:
-.BR MS_NOSUID ,
-.BR MS_NODEV ,
-.BR MS_NOEXEC .
+.\" files based on last access time) work correctly.
.TP
.BR MS_SILENT " (since Linux 2.6.17)"
Suppress the display of certain
.BR MS_VERBOSE
flag (available since Linux 2.4.12), which has the same meaning.
.TP
-.BR MS_STRICTATIME " (Since Linux 2.6.30)"
+.BR MS_STRICTATIME " (since Linux 2.6.30)"
Always update the last access time (atime) when files on this
-file system are accessed.
+filesystem are accessed.
(This was the default behavior before Linux 2.6.30.)
Specifying this flag overrides the effect of setting the
.BR MS_NOATIME
flags.
.TP
.B MS_SYNCHRONOUS
-Make writes on this file system synchronous (as though
+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 file system).
+was specified for all file opens to this filesystem).
.PP
From Linux 2.4 onward, the
.BR MS_NODEV ", " MS_NOEXEC ", and " MS_NOSUID
The
.B MS_RELATIME
flag is also settable on a per-mount-point basis.
+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.
+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.
.PP
The
+.I source
+and
+.I filesystemtype
+arguments are ignored.
+.PP
+The
+.I mountflags
+and
.I data
-argument is interpreted by the different file systems.
-Typically it is a string of comma-separated options
-understood by this file system.
-See
-.BR mount (8)
-for details of the options available for each filesystem type.
-.SH "RETURN VALUE"
+arguments should match the values used in the original
+.BR mount ()
+call, except for those parameters that are being deliberately changed.
+Another exception is that
+.B MS_BIND
+has a different meaning for remount, and it should be included only if
+explicitly desired.
+.PP
+The following
+.I mountflags
+can be changed:
+.BR MS_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 ,
+and
+.BR MS_SYNCHRONOUS .
+Attempts to change the setting of the
+.\" See the definition of MS_RMT_MASK in include/uapi/linux/fs.h
+.BR MS_DIRSYNC
+flag during a remount are silently ignored.
+.PP
+Since Linux 3.17,
+.\" commit ffbc6f0ead47fa5a1dc9642b0331cb75c20a640e
+if none of
+.BR MS_NOATIME ,
+.BR MS_NODIRATIME ,
+.BR MS_RELATIME ,
+or
+.BR 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 ).
+.PP
+Since Linux 2.6.26, this 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 point without changing the underlying filesystem.
+Specifying
+.IR mountflags
+as:
+.PP
+ MS_REMOUNT | MS_BIND | MS_RDONLY
+.PP
+will make access through this mountpoint read-only, without affecting
+other mount points.
+.\"
+.SS Creating a bind mount
+If
+.I mountflags
+includes
+.BR MS_BIND
+(available since Linux 2.4),
+.\" since 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.
+.PP
+The
+.IR filesystemtype
+and
+.IR data
+arguments are ignored.
+.PP
+The remaining bits in the
+.I mountflags
+argument are also ignored, with the exception of
+.BR MS_REC .
+(The bind mount has the same mount options as
+the underlying mount point.)
+However, see the discussion of remounting above,
+for a method of making an existing bind mount read-only.
+.PP
+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
+.BR 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
+.IR mountflags
+includes one of
+.BR MS_SHARED ,
+.BR MS_PRIVATE ,
+.BR MS_SLAVE ,
+or
+.BR 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.
+.PP
+The only flags that can be used with changing the propagation type are
+.BR MS_REC
+and
+.BR MS_SILENT .
+.PP
+The
+.IR source ,
+.IR filesystemtype ,
+and
+.IR data
+arguments are ignored.
+.PP
+The meanings of the propagation type flags are as follows:
+.TP
+.BR MS_SHARED
+Make this mount point shared.
+Mount and unmount events immediately under this mount point will propagate
+to the other mount points 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 mount points in the peer group.
+Conversely, mount and unmount events that take place under
+peer mount points will propagate to this mount point.
+.TP
+.BR MS_PRIVATE
+Make this mount point private.
+Mount and unmount events do not propagate into or out of this mount point.
+.TP
+.BR MS_SLAVE
+If this is a shared mount point that is a member of a peer group
+that contains other members, convert it to a slave mount.
+If this is a shared mount point 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 point is left unchanged.
+.PP
+When a mount point is a slave,
+mount and unmount events propagate into this mount point from
+the (master) shared peer group of which it was formerly a member.
+Mount and unmount events under this mount point do not propagate to any peer.
+.PP
+A mount point 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
+.BR 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
+.BR MS_BIND
+and
+.BR MS_REC
+flags) is performed on a directory subtree,
+any bind mounts within the subtree are automatically pruned
+(i.e., not replicated)
+when replicating that subtree to produce the target subtree.
+.PP
+By default, changing the propagation type affects only the
+.I target
+mount point.
+If the
+.B MS_REC
+flag is also specified in
+.IR mountflags ,
+then the propagation type of all mount points under
+.IR target
+is also changed.
+.PP
+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
+.BR MS_MOVE
+(available since Linux 2.4.18),
+then move a subtree:
+.I source
+specifies an existing mount point and
+.I target
+specifies the new location to which that mount point is to be relocated.
+The move is atomic: at no point is the subtree unmounted.
+.PP
+The remaining bits in the
+.IR mountflags
+argument are ignored, as are the
+.IR filesystemtype
+and
+.IR data
+arguments.
+.\"
+.SS Creating a new mount point
+If none of
+.BR MS_REMOUNT ,
+.BR MS_BIND ,
+.BR MS_MOVE ,
+.BR MS_SHARED ,
+.BR MS_PRIVATE ,
+.BR MS_SLAVE ,
+or
+.BR MS_UNBINDABLE
+is specified in
+.IR mountflags ,
+then
+.BR mount ()
+performs its default action: creating a new mount point.
+.IR source
+specifies the source for the new mount point, and
+.IR target
+specifies the directory at which to create the mount point.
+.PP
+The
+.I filesystemtype
+and
+.I data
+arguments are employed, and further bits may be specified in
+.IR mountflags
+to modify the behavior of the call.
+.\"
+.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
.SH ERRORS
The error values given below result from filesystem type independent
errors.
-Each file-system type may have its own special errors and its
+Each filesystem type may have its own special errors and its
own special behavior.
See the Linux kernel source code for details.
.TP
A component of a path was not searchable.
(See also
.BR path_resolution (7).)
-Or, mounting a read-only file system was attempted without giving the
+.TP
+.B EACCES
+Mounting a read-only filesystem was attempted without giving the
.B MS_RDONLY
flag.
-Or, the block device
+.TP
+.B EACCES
+The block device
.I source
-is located on a file system mounted with the
+is located on a filesystem mounted with the
.B MS_NODEV
option.
.\" mtk: Probably: write permission is required for MS_BIND, with
.B EBUSY
.I source
is already mounted.
-Or, it cannot be remounted read-only,
+.TP
+.B EBUSY
+.I source
+cannot be remounted read-only,
because it still holds files open for writing.
-Or, it cannot be mounted on
+.TP
+.B EBUSY
+.I source
+cannot be mounted on
.I target
because
.I target
.B EINVAL
.I source
had an invalid superblock.
-Or, a remount
+.TP
+.B EINVAL
+A remount operation
.RB ( MS_REMOUNT )
was attempted, but
.I source
was not already mounted on
.IR target .
-Or, a move
+.TP
+.B EINVAL
+A move operation
.RB ( MS_MOVE )
was attempted, but
.I source
was not a mount point, or was \(aq/\(aq.
.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
+.BR MS_UNBINDABLE
+and also includes a flag other than
+.BR MS_REC
+or
+.BR MS_SILENT .
+.TP
+.BR EINVAL
+An attempt was made to bind mount an unbindable mount.
+.TP
.B ELOOP
Too many links encountered during pathname resolution.
-Or, a move was attempted, while
+.TP
+.B ELOOP
+A move operation was attempted, and
.I target
is a descendant of
.IR source .
The definitions of
.BR MS_DIRSYNC ,
.BR MS_MOVE ,
+.BR MS_PRIVATE ,
.BR MS_REC ,
.BR MS_RELATIME ,
-and
+.BR MS_SHARED ,
+.BR MS_SLAVE ,
.BR MS_STRICTATIME
+and
+.BR MS_UNBINDABLE
were added to glibc headers in version 2.12.
-.\" FIXME: Definitions of the so-far-undocumented MS_UNBINDABLE, MS_PRIVATE,
-.\" MS_SHARED, and MS_SLAVE were (also) only added to glibc headers in 2.12.
-.SH "CONFORMING TO"
+.\"
+.SH CONFORMING TO
This function is Linux-specific and should not be used in
programs intended to be portable.
.SH NOTES
+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 2.3.99pre7.
+.PP
+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
+.BR MS_MGC_VAL
+was required in kernel versions prior to 2.4,
+but since Linux 2.4 is no longer required and is ignored if specified.
+.PP
The original
.B MS_SYNC
flag was renamed
was added to \fI<mman.h>\fP.
.LP
Before Linux 2.4 an attempt to execute a set-user-ID or set-group-ID program
-on a file system mounted with
+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.
+.\"
.SS Per-process namespaces
Starting with kernel 2.4.19, Linux provides
per-process mount namespaces.
-A mount namespace is the set of file system mounts that
+A mount namespace is the set of filesystem mounts that
are visible to a process.
Mount-point namespaces can be (and usually are)
shared between multiple processes,
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.)
-
+.PP
A child process created by
.BR fork (2)
shares its parent's mount namespace;
the mount namespace is preserved across an
.BR execve (2).
-
+.PP
A process can obtain a private mount namespace if:
it was created using the
.BR clone (2)
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.
-
+.PP
The Linux-specific
-.I /proc/PID/mounts
+.I /proc/[pid]/mounts
file exposes the list of mount points in the mount
namespace of the process with the specified ID; see
.BR proc (5)
for details.
-.SH "SEE ALSO"
+.SH SEE ALSO
+.BR mountpoint (1),
.BR umount (2),
-.BR namespaces (7),
+.BR mount_namespaces (7),
.BR path_resolution (7),
+.BR findmnt (8),
+.BR lsblk (8),
.BR mount (8),
.BR umount (8)
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