Re: /etc/mtab and per-process namespaces

From: Rob Landley (rob_at_landley.net)
Date: 11/01/05

  • Next message: Brian Louise: "Dear friend" 
    To: Ram Pai <linuxram@us.ibm.com>
Date:	Mon, 31 Oct 2005 17:27:26 -0600

    On Monday 31 October 2005 13:11, Ram Pai wrote:
    > > The big thing I've never figured out how to do is make umount -a work in
    > > the presence of multiple namespaces. (Should it just umount what it
    > > sees? I don't know how to umount everything because I can't find
    > > everything...)
    >
    > Yes you won't find everything, since some of them are in a different
    > namespaces. Instead unmount whatever you see. Or use /proc/mounts
    > to unmount whatever is there in its namespace.

    But /proc/mounts is a symlink to self/mounts, and self is a symlink to $PID,
    so after burrowing through the symlinks you wind up looking
    at /proc/$PID/mounts.

    My concern is that if I have init, as root, try to perform a umount -a, it
    _still_ won't get the mounts belonging to child processes with a separate
    namespace. There's no "global view" of mounts available anywhere.

    On the other hand, if we fork a child process with its own namespace, the
    child performs a private mount, and then we kill that child process, does
    that hidden mount get umounted cleanly via refcounting? (Or does it leak?)

    If killing the processes umounts their private mounts, all init has to do is
    make sure all child processes are dead before doing a umount -a on what's
    left. (Then, of course, there's FUSE. Does killing the FUSE helper prevent
    the mount from being umounted?)

    It's a bit conceptually persnickety, so far...

    Rob
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  • Next message: Brian Louise: "Dear friend"

    Relevant Pages

    • Re: Devlabel and Fstab with usb pendrive
      ... /etc/updfstab and now my TinyDisk pendrive mounts on /mnt/flash (which ... another user comes along they can umount it. ... Anyone know how to either use updfstab to get it to set these options ... Problem is this occurs even if the file browser ...
      (Fedora)
    • Re: /etc/mtab and per-process namespaces
      ... >> to unmount whatever is there in its namespace. ... > My concern is that if I have init, as root, try to perform a umount -a, it ... the mounts belonging its namespace'. ... > On the other hand, if we fork a child process with its own namespace, the ...
      (Linux-Kernel)
    • autofs4 /net /proc/mounts problem
      ... mounts not working. ... I’m guessing what’s happening next is autofs4 tries to umount foo:/ before ... If I bring down the automount process, manually go through and umount all ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    • Re: Are RWs a problem?
      ... finds it and mounts it. ... If it was not blank, wait for it to mount, start a CLI, and umount it ... there is k3b attempting to automount it. ... OK - memory is not the most reliable, but that's the general approach I use. ...
      (Fedora)