Lazy umount or Unmounting a busy disk in Linux

Posted by deed02392 on Super User See other posts from Super User or by deed02392
Published on 2012-04-13T14:47:24Z Indexed on 2012/04/13 17:34 UTC
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linux

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umount

I have read that it is possible to 'umount' a disk that is otherwise busy by using the 'lazy' option. The manpage has this to say about it:

umount - unmount file systems

-l 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. This option allows a "busy" filesystem to be unmounted. (Requires kernel 2.4.11 or later.)

But what would be the point in that? I considered why we dismount partitions at all:

To remove the hardware
To perform operations on the filesystem that would be unsafe to do while mounted

In either of these cases, all a 'lazy' unmount serves IMHO is to make it more difficult to determine if the disk really is dismounted and you can actually proceed with these actions. The only application for umount -l seems to be for inexperienced users to 'feel' like they've achieved something they haven't.

Why would you use a lazy unmount?

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