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umount(8) [centos man page]

UMOUNT(8)						       System Administration							 UMOUNT(8)

NAME
umount - unmount file systems SYNOPSIS
umount [-hV] umount -a [-dflnrv] [-t vfstype] [-O options] umount [-dflnrv] {dir|device}... DESCRIPTION
The umount command detaches the file system(s) mentioned from the file hierarchy. A file system is specified by giving the directory where it has been mounted. Giving the special device on which the file system lives may also work, but is obsolete, mainly because it will fail in case this device was mounted on more than one directory. Note that a file system cannot be unmounted when it is 'busy' - for example, when there are open files on it, or when some process has its working directory there, or when a swap file on it is in use. The offending process could even be umount itself - it opens libc, and libc in its turn may open for example locale files. A lazy unmount avoids this problem. OPTIONS
-a, --all All of the file systems described in /etc/mtab are unmounted. (With umount version 2.7 and later: the proc filesystem is not unmounted.) -A, --all-targets Unmount all mountpoints in the current namespace for the specified filesystem. The filesystem could be specified by one of the mountpoints or device name (or UUID, etc.). This option could be used together with --recursive then all nested mounts within the filesystem are recursively unmounted. -c, --no-canonicalize Do not canonicalize paths. For more details about this option see the mount(8) man page. -d, --detach-loop In case the unmounted device was a loop device, also free this loop device. --fake Causes everything to be done except for the actual system call; this 'fakes' unmounting the filesystem. It can be used to remove entries from /etc/mtab that were unmounted earlier with the -n option. -f, --force Force unmount (in case of an unreachable NFS system). (Requires kernel 2.1.116 or later.) -i, --internal-only Do not call the /sbin/umount.<filesystem> helper even if it exists. By default /sbin/umount.<filesystem> helper is called if one exists. -n, --no-mtab Unmount without writing in /etc/mtab. -l, --lazy Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all references to the filesystem as soon as it is not busy anymore. (Requires kernel 2.4.11 or later.) -O, --test-opts options,list Indicate that the actions should only be taken on file systems with the specified options in /etc/fstab. More than one option type may be specified in a comma separated list. Each option can be prefixed with no to specify options for which no action should be taken. -R, --recursive Recursively unmount each directory specified. Recursion for each directory will stop if any unmount operation in the chain fails for any reason. The relationship between mountpoints is determined by /proc/self/mountinfo entries. The filesystem must be specified by mountpoint path, recursive unmount by device name (or UUID) is unsupported. -r, --read-only In case unmounting fails, try to remount read-only. -t, --types vfstype,ext2,ext3 Indicate that the actions should only be taken on file systems of the specified type. More than one type may be specified in a comma separated list. The list of file system types can be prefixed with no to specify the file system types on which no action should be taken. -v, --verbose Verbose mode. -h, --help Print help message and exit. -V, --version Print version and exit. THE LOOP DEVICE
The umount command will free the loop device (if any) associated with the mount, in case it finds the option 'loop=...' in /etc/mtab, or when the -d option was given. Any pending loop devices can be freed using 'losetup -d', see losetup(8). NOTES
The syntax of external umount helpers is: /sbin/umount.<suffix> {dir|device} [-nlfvr] [-t type.subtype] where the <suffix> is filesystem type or a value from "uhelper=" or "helper=" mtab option. The -t option is used for filesystems with sub- types support (for example /sbin/mount.fuse -t fuse.sshfs). The uhelper= (unprivileged umount helper) is possible to use when non-root user wants to umount a mountpoint which is not defined in the /etc/fstab file (e.g. devices mounted by udisk). The helper= mount option redirects all umount requests to the /sbin/umount.<helper> independently on UID. FILES
/etc/mtab table of mounted file systems ENVIRONMENT
LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file LIBMOUNT_MTAB=<path> overrides the default location of the mtab file LIBMOUNT_DEBUG=0xffff enables debug output SEE ALSO
umount(2), mount(8), losetup(8) HISTORY
A umount command appeared in Version 6 AT&T UNIX. AVAILABILITY
The umount command is part of the util-linux package and is available from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util- linux/>. util-linux August 2012 UMOUNT(8)

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