Re: Which process context does /sbin/hotplug run in?

[Joshua Hudson]

> > And I'm not _complaining_ about it.  Just fiddling around with fun
> > stuff.  If I get really bored I'll figure a way to split the tree
> > so there are two completely unconnected mount trees in different
> > processes.  (Get a private  namespace that's chrooted into
> > something that somebody else does a umount -l on from their space.
> > Or without using umount -l, just have two processes chroot into
> > other mount points which should theoretically garbage collect the
> > old root if no processes still references it, which presumably
> > means one of the processes is init...)
>
> Well, actually, it isn't that hard.  Just run something like this:
>
> #! /bin/sh
> mkdir /a
> mkdir /b
> mount -t tmpfs tmpfs /a
> mount -t tmpfs tmpfs /b
> mkdir /a/old
> mkdir /b/old
> tool_to_fork_in_new_namespace sh -c "pivot_root /a /a/old && umount -
> l /a/old && read"
> pivot_root /b /b/old && umount -l /b/old && read
>
> All you need to write is tool_to_fork_in_new_namespace which does
> clone(CLONE_NEWNS) followed by exec().
>
> Cheers,
> Kyle Moffett
I've done that "two disconnected trees" in 2.0 kernel. Boot with an initrd.
/linuxrc runs something in the background (telnet server, just for kicks)
/initrd doesn't exist ont the new root.
So, try mount new root succeeds, but try unmount old root fails.
Presto. Two disconnected trees.

I wonder if it still works.
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