2008-10-06 11:09:26 +00:00
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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.\" manual page may be incorrect or out-of-date.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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2010-06-19 03:39:31 +00:00
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.TH UMOUNT 2 2010-06-19 "Linux" "Linux Programmer's Manual"
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2008-10-06 11:09:26 +00:00
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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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.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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2010-06-19 03:39:31 +00:00
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.TP
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.BR UMOUNT_NOFOLLOW " (since Linux 2.6.34)"
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2010-06-26 08:56:15 +00:00
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.\" Later added to 2.6.33-stable
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2010-06-19 03:39:31 +00:00
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Don't dereference
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.I target
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if it is a symbolic link.
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2010-08-29 04:40:29 +00:00
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This flag allows security problems to be avoided in set-user-ID-\fIroot\fP
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2010-06-19 03:39:31 +00:00
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programs that allow unprivileged users to unmount file systems.
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2008-10-06 11:09:26 +00:00
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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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2010-06-15 03:16:42 +00:00
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The error values given below result from file-system type independent
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2008-10-06 11:09:26 +00:00
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errors.
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2010-06-15 03:16:42 +00:00
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Each file system type may have its own special errors and its
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2008-10-06 11:09:26 +00:00
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own special behavior.
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bdflush.2, get_robust_list.2, kexec_load.2, madvise.2, mmap.2, mount.2, prctl.2, query_module.2, rt_sigqueueinfo.2, shmget.2, sigaction.2, syscalls.2, umount.2, malloc.3, hpsa.4, initrd.4, proc.5, bootparam.7, icmp.7, netlink.7, signal.7: Global fix: use "Linux kernel source" consistently
Rather than "kernel source".
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2012-09-24 08:02:34 +00:00
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See the Linux kernel source code for details.
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2008-10-06 11:09:26 +00:00
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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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2009-09-03 04:06:54 +00:00
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.SH VERSIONS
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.BR MNT_DETACH
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and
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.BR MNT_EXPIRE
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2009-09-03 04:07:57 +00:00
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.\" http://sourceware.org/bugzilla/show_bug.cgi?id=10092
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2009-09-03 04:06:54 +00:00
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are only available in glibc since version 2.11.
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2008-10-06 11:09:26 +00:00
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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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