On Friday 11 January 2013 19:54:16 Phillip Susi wrote: > On 01/11/2013 06:52 PM, Mike Frysinger wrote: > > On Thursday 03 May 2012 10:29:07 Phillip Susi wrote: > >> If you want to hide mounts from certain processes, that is what > >> unshare is for. Hiding a mount from all processes does not make > >> sense. If you know a mount is gone and beyond recovery ( like in > >> this loop over nfs case, or removed media ), then it should be > >> forcibly unmounted, not simply made invisible and doomed to > >> remain a zombie mount until the system is rebooted. > > > > in an ideal world, maybe unshare might work. in the real world, it > > doesn't. you can use it only on *new* processes, not ones that are > > already running. nor can you do `unshare shutdown` and have it work > > since that simply signals a long running init process to initiate a > > shutdown. > > > > an nfs server goes afk and attempts to `umount` it timeout, as well > > as many desktop programs (like kde io daemons that like to walk > > available mount points) or shutdown processes. no call to > > `unshare` will fix this, but certainly forcibly removing it with > > `umount -l` will. > > A bit of a delayed response there the recent unshare patches reminded me of this. and i had actually used unshare in the interim so i know how it works now. > but my point was that what you are > looking for is umount -f, not umount -l. and my point is that `umount -f` doesn't always work which means `umount -l` is sometimes the only way to remove a mount point. an unresponsive remote or something is holding open a reference (which doesn't show up in `lsof -n`). > It also used to be that once > you detached a mount with umount -l, you could not reattach it. > Attempts to remount would fail with EBUSY and so this was a horribly > broken state to be in. At some point it seems this was changed and > now you *can* reattach, so lazy unmount is no longer pure evil, but > still it is no forced unmount. it hasn't been that way for quite some time, and for network based mounts, it's pretty much never been that way ? -mike
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