From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 28 Nov 2014 13:15:36 +0100 From: Gilles Chanteperdrix Message-ID: <20141128121536.GE6395@hermes> References: <20141127203400.GP7842@hermes> <54778CF6.6000909@siemens.com> <20141127231527.GC24076@hermes> <5478430B.9030602@siemens.com> <20141128095038.GA3832@hermes> <547846AC.6070204@siemens.com> <20141128095745.GB3832@hermes> <5478618F.1010506@siemens.com> <20141128115537.GB6395@hermes> <54786583.5080205@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54786583.5080205@siemens.com> Subject: Re: [Xenomai] [pull] forge: Adjust default registry mount point List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Xenomai On Fri, Nov 28, 2014 at 01:07:31PM +0100, Jan Kiszka wrote: > On 2014-11-28 12:55, Gilles Chanteperdrix wrote: > > On Fri, Nov 28, 2014 at 12:50:39PM +0100, Jan Kiszka wrote: > >> On 2014-11-28 10:57, Gilles Chanteperdrix wrote: > >>> On Fri, Nov 28, 2014 at 10:55:56AM +0100, Jan Kiszka wrote: > >>>> On 2014-11-28 10:50, Gilles Chanteperdrix wrote: > >>>>> On Fri, Nov 28, 2014 at 10:40:27AM +0100, Jan Kiszka wrote: > >>>>>> On 2014-11-28 00:15, Gilles Chanteperdrix wrote: > >>>>>>> On Thu, Nov 27, 2014 at 09:43:34PM +0100, Jan Kiszka wrote: > >>>>>>>> On 2014-11-27 21:34, Gilles Chanteperdrix wrote: > >>>>>>>>> On Thu, Nov 27, 2014 at 02:14:38PM -0500, Lennart Sorensen wrote: > >>>>>>>>>> On Thu, Nov 27, 2014 at 07:51:27PM +0100, Jan Kiszka wrote: > >>>>>>>>>>> On 2014-11-27 19:18, Gilles Chanteperdrix wrote: > >>>>>>>>>>>> According to the filesystem hierarchy standard, /mnt is the standard > >>>>>>>>>>>> place for "temporarily mounted filesystems". > >>>>>>>>>>>> > >>>>>>>>>>>> http://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard > >>>>>>>>>>> > >>>>>>>>>>> Right, another reason to NOT mess around with it: if something was > >>>>>>>>>>> temporarily mounted there, we will create the mountpoint inside that > >>>>>>>>>>> filesystem with unforeseeable side effects. > >>>>>>>>>> > >>>>>>>>>> I always read that as "temporarily mounted there by the admin or some > >>>>>>>>>> other human". Certainly not automatic mounts by software. There is a > >>>>>>>>>> reason /media and such exists on many distributins. > >>>>>>>>> > >>>>>>>>> I would not venture an "always", autofs for instance, used to mount > >>>>>>>>> things under /mnt. and /media has not always existed either, we used > >>>>>>>>> /mnt/cdrom. > >>>>>>>> > >>>>>>>> FHS on /mnt purpose: > >>>>>>>> > >>>>>>>> "This directory is provided so that the system administrator may > >>>>>>>> temporarily mount a filesystem as needed. The content of this directory > >>>>>>>> is a local issue and should not affect the manner in which any program > >>>>>>>> is run." > >>>>>>>> > >>>>>>>> I think this makes it crystal clear that Xenomai is not supposed to > >>>>>>>> touch it. > >>>>>>> > >>>>>>> Just to add another argument. I just asked a friend who is a > >>>>>>> professional sysadmin. He creates directory under /mnt and mount > >>>>>>> things under these directories. So, I am not sure the standard is > >>>>>>> even applied by the people who should use it. > >>>>>>> > >>>>>>> If you read on the last site I sent, under the /media article: > >>>>>>> > >>>>>>> Amid much controversy and consternation on the part of system and > >>>>>>> network administrators a directory containing mount points for > >>>>>>> removable media has now been created. Funnily enough, it has been > >>>>>>> named /media. > >>>>>>> > >>>>>>> Are you sure, 100% sure, that every Xenomai user expects to be able > >>>>>>> to use /mnt as a mount point? Or that they will create directories > >>>>>>> under /mnt like everybody has been doing since Linux exists? > >>>>>> > >>>>>> I'm both absolutely sure that a) has to be left alone by Xenomai because > >>>>>> of requirements of the FHS and the way /mnt is used and b) we should try > >>>>>> hard to avoid creating temporary dirs in persistent filesystems. > >>>>> > >>>>> This is ridiculous. Because the standard changed, and one > >>>>> distribution, Debian, decided to follow the new standard, which > >>>>> seems to be not widely accepted, and even controversial, you want to > >>>>> impose what Debian does to everybody. The distribution I use has > >>>>> mount points under /mnt. So, why following Debian and not the > >>>>> distribution I use, and what sysadmin have been doing for ages? > >>>>> > >>>>> You want the mount point to be somewhere else? Fine, put a symbolic > >>>>> link. > >>>>> > >>>>> mkdir /run/xenomai > >>>>> ln -s /run/xenomai /mnt/xenomai > >>>> > >>>> Again, this is not acceptible as /mnt changes all the time and exposes > >>>> various remote filesystems which will hide that link. > >>> > >>> You are missing the point. Yes, Debian does that, but not all > >>> distribution. Other distributions do not do that. > >>> > >> > >> SUSE, Ubuntu, Gentoo, Red Hat - it's already standard. But I will change > >> my patch to /var/run to avoid surprises with other/older distros. > > > > Again, using /mnt/xenomai does not break any distribution following > > the standard. > > > > Let us try things another way, the possibilities we have are: > > - /mnt/xenomai: a solution that used to be standard but ceased to be > > with the FHS which did not provide a standard replacement, but does > > not break any distribution > > I don't remember that this was ever a standard. My distro (SUSE) never > used it like this as long as I can remember (~18 year). > > > - /run/xenomai: a solution that relies on the existence on the /run > > directory, which is not standard, but is going to be, maybe. > > - /var/run/xenomai: a solution which does not violate any version of > > the standard, but is not standard either, does not make clear that > > the directory is a mount point (which /mnt does), breaks the > > This is how it's used in practice: > > gvfsd-fuse on /var/run/user/1000/gvfs type fuse.gvfsd-fuse > (rw,nosuid,nodev,relatime,user_id=1000,group_id=100) It does not seem to be standard. Mine uses: gvfsd-fuse on /home/gilles/.gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=gilles) That is the problem: the FHS standard does not define an equivalent to what /mnt used to be. So, everyone mount things wherever he wants. -- Gilles.