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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?
So how do you know when the disk operations are done?
See this example (bug?) of being able to write a file to an already unmounted filesystem
If you were lazy, surely you would want to save MORE time by not having to use the argument, because once you got back you knew you could dismount it immediately now the backup has finished? Or make dismounting the drive part of the post-backup operations? – deed02392 – 2012-04-13T15:10:26.443
Think of it this way: the disk is no longer busy - unmount it now. It's no longer mounted so nothing else can write to it. It's "do this when you can" instead of erroring out. – Broam – 2012-04-13T19:07:07.303