mirror of https://github.com/mkerrisk/man-pages
mount.2, umount.2: split umoun*() out into a separate page
The length of this page means that it's becoming difficult to parse which info is specific to mount() versus umount()/umount2(), so split the umount material out into its own page. Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk
parent
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99
man2/mount.2
99
man2/mount.2
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@ -35,9 +35,9 @@
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.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
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.\" 2005-05-18, mtk, Added MNT_EXPIRE, plus a few other tidy-ups.
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.\"
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.TH MOUNT 2 2008-10-02 "Linux" "Linux Programmer's Manual"
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.TH MOUNT 2 2008-10-06 "Linux" "Linux Programmer's Manual"
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.SH NAME
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mount, umount, umount2 \- mount and unmount file systems
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mount \- mount file system
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.SH SYNOPSIS
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.nf
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.B "#include <sys/mount.h>"
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@ -45,13 +45,8 @@ mount, umount, umount2 \- mount and unmount file systems
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.BI "int mount(const char *" source ", const char *" target ,
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.BI " const char *" filesystemtype ", unsigned long " mountflags ,
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.BI " const void *" data );
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.sp
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.BI "int umount(const char *" target );
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.sp
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.BI "int umount2(const char *" target ", int " flags );
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.fi
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.SH DESCRIPTION
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.\" FIXME . This page could be better structured
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.BR mount ()
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attaches the file system specified by
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.I source
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@ -59,15 +54,9 @@ attaches the file system specified by
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or a dummy) to the directory specified by
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.IR target .
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.BR umount ()
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and
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.BR umount2 ()
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remove the attachment of the (topmost) file system mounted on
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.IR target .
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Appropriate privilege (Linux: the
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.B CAP_SYS_ADMIN
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capability) is required to mount and unmount file systems.
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capability) is required to mount file systems.
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Since Linux 2.4 a single file system can be visible at
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multiple mount points, and multiple mounts can be stacked
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@ -263,49 +252,6 @@ understood by this file system.
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See
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.BR mount (8)
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for details of the options available for each filesystem type.
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.PP
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.\" Note: the kernel naming differs from the glibc naming
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.\" umount2 is the glibc name for what the kernel now calls umount
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.\" and umount is the glibc name for oldumount
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Linux 2.1.116 added the
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.BR umount2 ()
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system call, which, like
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.BR umount (),
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unmounts a target, but allows additional
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.I flags
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controlling the behavior of the operation:
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.TP
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.BR MNT_FORCE " (since Linux 2.1.116)"
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Force unmount even if busy.
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This can cause data loss.
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(Only for NFS mounts.)
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.\" FIXME Can MNT_FORCE result in data loss? According to
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.\" the Solaris manual page it can cause data loss on Solaris.
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.\" If the same holds on Linux, then this should be documented.
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.TP
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.BR MNT_DETACH " (since Linux 2.4.11)"
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Perform a lazy unmount: make the mount point unavailable for
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new accesses, and actually perform the unmount when the mount point
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ceases to be busy.
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.TP
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.BR MNT_EXPIRE " (since Linux 2.6.8)"
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Mark the mount point as expired.
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If a mount point is not currently in use, then an initial call to
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.BR umount2 ()
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with this flag fails with the error
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.BR EAGAIN ,
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but marks the mount point as expired.
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The mount point remains expired as long as it isn't accessed
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by any process.
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A second
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.BR umount2 ()
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call specifying
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.B MNT_EXPIRE
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unmounts an expired mount point.
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This flag cannot be specified with either
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.B MNT_FORCE
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or
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.BR MNT_DETACH .
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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@ -333,13 +279,6 @@ option.
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.\" mtk: Probably: write permission is required for MS_BIND, with
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.\" the error EPERM if not present; CAP_DAC_OVERRIDE is required.
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.TP
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.B EAGAIN
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A call to
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.BR umount2 ()
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specifying
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.B MNT_EXPIRE
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successfully marked an unbusy file system as expired.
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.TP
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.B EBUSY
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.I source
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is already mounted.
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@ -351,7 +290,6 @@ because
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.I target
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is still busy (it is the working directory of some task,
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the mount point of another device, has open files, etc.).
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Or, it could not be unmounted because it is busy.
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.TP
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.B EFAULT
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One of the pointer arguments points outside the user address space.
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@ -370,17 +308,6 @@ Or, a move
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was attempted, but
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.I source
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was not a mount point, or was \(aq/\(aq.
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Or, an unmount was attempted, but
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.I target
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was not a mount point.
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Or,
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.BR umount2 ()
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was called with
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.B MNT_EXPIRE
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and either
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.B MNT_DETACH
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or
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.BR MNT_FORCE .
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.TP
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.B ELOOP
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Too many links encountered during pathname resolution.
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@ -412,8 +339,10 @@ The kernel could not allocate a free page to copy filenames or data into.
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is not a block device (and a device was required).
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.TP
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.B ENOTDIR
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The second argument, or a prefix of the first argument, is not
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a directory.
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.IR target ,
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or a prefix of
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.IR source ,
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is not a directory.
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.TP
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.B ENXIO
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The major number of the block device
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@ -423,22 +352,11 @@ is out of range.
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.B EPERM
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The caller does not have the required privileges.
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.SH "CONFORMING TO"
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These functions are Linux-specific and should not be used in
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This function is Linux-specific and should not be used in
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programs intended to be portable.
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.SH NOTES
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.SS Linux Notes
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The original
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.BR umount ()
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function was called as \fIumount(device)\fP and would return
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.B ENOTBLK
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when called with something other than a block device.
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In Linux 0.98p4 a call \fIumount(dir)\fP was added, in order to
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support anonymous devices.
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In Linux 2.3.99-pre7 the call \fIumount(device)\fP was removed,
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leaving only \fIumount(dir)\fP (since now devices can be mounted
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in more than one place, so specifying the device does not suffice).
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.LP
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The original
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.B MS_SYNC
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flag was renamed
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.B MS_SYNCHRONOUS
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@ -456,6 +374,7 @@ Since Linux 2.4 the set-user-ID and set-group-ID bits are
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just silently ignored in this case.
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.\" The change is in patch-2.4.0-prerelease.
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.SH "SEE ALSO"
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.BR umount (2),
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.BR path_resolution (7),
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.BR mount (8),
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.BR umount (8)
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164
man2/umount.2
164
man2/umount.2
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@ -1 +1,163 @@
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.so man2/mount.2
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.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright (C) 1993 Rickard E. Faith <faith@cs.unc.edu>
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.\" and Copyright (C) 1994 Andries E. Brouwer <aeb@cwi.nl>
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.\" and Copyright (C) 2002, 2005 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" 2008-10-06, mtk: Created this as a new page by splitting
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.\" umount/umount2 material out of mount.2
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.\"
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.TH UMOUNT 2 2008-10-06 "Linux" "Linux Programmer's Manual"
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.SH NAME
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umount, umount2 \- unmount file system
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.SH SYNOPSIS
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.nf
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.B "#include <sys/mount.h>"
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.sp
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.BI "int umount(const char *" target );
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.sp
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.BI "int umount2(const char *" target ", int " flags );
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.fi
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.SH DESCRIPTION
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.BR umount ()
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and
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.BR umount2 ()
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remove the attachment of the (topmost) file system mounted on
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.IR target .
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.\" Note: the kernel naming differs from the glibc naming
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.\" umount2 is the glibc name for what the kernel now calls umount
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.\" and umount is the glibc name for oldumount
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Appropriate privilege (Linux: the
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.B CAP_SYS_ADMIN
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capability) is required to unmount file systems.
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Linux 2.1.116 added the
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.BR umount2 ()
|
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system call, which, like
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.BR umount (),
|
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unmounts a target, but allows additional
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.I flags
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controlling the behavior of the operation:
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.TP
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.BR MNT_FORCE " (since Linux 2.1.116)"
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Force unmount even if busy.
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This can cause data loss.
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(Only for NFS mounts.)
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.\" FIXME Can MNT_FORCE result in data loss? According to
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.\" the Solaris manual page it can cause data loss on Solaris.
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.\" If the same holds on Linux, then this should be documented.
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.TP
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.BR MNT_DETACH " (since Linux 2.4.11)"
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Perform a lazy unmount: make the mount point unavailable for
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new accesses, and actually perform the unmount when the mount point
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ceases to be busy.
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.TP
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.BR MNT_EXPIRE " (since Linux 2.6.8)"
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Mark the mount point as expired.
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If a mount point is not currently in use, then an initial call to
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.BR umount2 ()
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with this flag fails with the error
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.BR EAGAIN ,
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but marks the mount point as expired.
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The mount point remains expired as long as it isn't accessed
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by any process.
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A second
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.BR umount2 ()
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call specifying
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.B MNT_EXPIRE
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unmounts an expired mount point.
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This flag cannot be specified with either
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.B MNT_FORCE
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or
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.BR MNT_DETACH .
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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The error values given below result from filesystem type independent
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errors.
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Each filesystem type may have its own special errors and its
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own special behavior.
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See the kernel source code for details.
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.TP
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.B EAGAIN
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A call to
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.BR umount2 ()
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specifying
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.B MNT_EXPIRE
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successfully marked an unbusy file system as expired.
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.TP
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.B EBUSY
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.I target
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could not be unmounted because it is busy.
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.TP
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.B EFAULT
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.I target
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points outside the user address space.
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.TP
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.B EINVAL
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.I target
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is not a mount point.
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Or,
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.BR umount2 ()
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was called with
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.B MNT_EXPIRE
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and either
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.B MNT_DETACH
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or
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.BR MNT_FORCE .
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.TP
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.B ENAMETOOLONG
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A pathname was longer than
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.BR MAXPATHLEN .
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.TP
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.B ENOENT
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A pathname was empty or had a nonexistent component.
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.TP
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.B ENOMEM
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The kernel could not allocate a free page to copy filenames or data into.
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.TP
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.B EPERM
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The caller does not have the required privileges.
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.SH "CONFORMING TO"
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These functions are Linux-specific and should not be used in
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programs intended to be portable.
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.SH NOTES
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The original
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.BR umount ()
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function was called as \fIumount(device)\fP and would return
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.B ENOTBLK
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when called with something other than a block device.
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In Linux 0.98p4 a call \fIumount(dir)\fP was added, in order to
|
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support anonymous devices.
|
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In Linux 2.3.99-pre7 the call \fIumount(device)\fP was removed,
|
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leaving only \fIumount(dir)\fP (since now devices can be mounted
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in more than one place, so specifying the device does not suffice).
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.SH "SEE ALSO"
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.BR mount (2),
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.BR path_resolution (7),
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.BR mount (8),
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.BR umount (8)
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