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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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umount [options] [directory]

System administration command. Unmount filesystem specified by directory. You may also specify the filesystem by device name. umount announces to the system that the removable file structure previously mounted on the specified directory is to be removed. Any pending I/O for the filesystem is completed, and the file structure is flagged as clean. A busy filesystem cannot be unmounted.



Unmount all filesystems listed in /etc/mtab other than /proc.


If the unmounted device was a loop device, free the loop device too. See also the losetup command.


Force the unmount. This option requires kernel 2.1.116 or later.


Print help message and exit.


Lazy unmount. Detach the filesystem from the hierarchy immediately, but don't clean up references until it is no longer busy. Requires kernel 2.4.11 or later.


Unmount, but do not record changes in /etc/mtab.

-O options

Unmount only filesystems with the specified options in /etc/fstab. Specify multiple options as a comma-separated list. Add no as a prefix to an option to indicate filesystems that should not be unmounted.


If unmounting fails, try to remount read-only.

-t type

Unmount only filesystems of type type. Multiple types can be specified as a comma-separated list, and any type can be prefixed with no to specify that filesystems of that type should not be unmounted.


Verbose mode.


Print version information and exit.

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