Re: umount without sync
On Fri, Sep 17, 2010 at 02:32:35PM CEST, Timo Juhani Lindfors <timo.lindfors@iki.fi> said:
> T o n g <mlist4suntong@yahoo.com> writes:
> > I saw that it is a common practice to issue sync several times before
> > umount. I know it's a good practice, but is it really necessary?
>
> There have been some bugs afaik and a sync has been a workaround.
>
> > If I copy a big chuck of file to my USB, then issue umount immediately,
> > will I lost any data? I think Linux will make sure all data are flushed
> > to USB before the umount is successfully finished, but I want a confirm.
>
> You should not lose any data if you wait for umount to succeed afaik.
>
> > How about umount swaps? umount really necessary?
>
> You don't mount swaps so you can't umount them either.
>
>
once a upon a time, in a far far away version of unix, umount might
return without having really fished writing data on disc. Thus admins
issued sync command(s) before unmounting to ensure the data was really
written.
Old storys even says that the magical incantation was
sync;sync;sync
wait completion
umount
--
Erwan
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