Bug#2016: SysVinit, mount] SysVinit uses non-existant option for umount
I've reconsidered this, and I think it really is a problem with umount.
Although in the general case `umount -a -n' should never be necessary, there
are exceptional cases where the root filesystem is remounted read-only *after*
/etc/mtab has been updated with other mounts.
I think it's probably best that `umount' be as flexible as possible. I've sent
a request to the util-linux maintainers to see why they changed it and if the
option can be restored.