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From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Nick Andrew <nick@nick-andrew.net>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>,
	trivial@kernel.org, linux-kernel@vger.kernel.org,
	Pavel Emelyanov <xemul@openvz.org>,
	Randy Dunlap <randy.dunlap@oracle.com>,
	Paul Menage <menage@google.com>, Paul Jackson <pj@sgi.com>,
	Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Subject: Re: [PATCH 2.6.25-rc2 3/9] Kconfig: Improve init/Kconfig help descriptions - NAMESPACES
Date: Fri, 22 Feb 2008 21:45:39 -0600	[thread overview]
Message-ID: <20080223034539.GA22100@sergelap.austin.ibm.com> (raw)
In-Reply-To: <20080223011258.GH2169@tull.net>

Quoting Nick Andrew (nick@nick-andrew.net):
> On Fri, Feb 22, 2008 at 04:14:12PM -0600, Serge E. Hallyn wrote:
> > Quoting Nick Andrew (nick@nick-andrew.net):
> > >  config UTS_NS
> > >  	bool "UTS namespace"
> > >  	depends on NAMESPACES
> > >  	help
> > > -	  In this namespace tasks see different info provided with the
> > > -	  uname() system call
> > > +	  Enable support for multiple UTS system attributes.
> > > +
> > > +	  Each UTS namespace provides an individual view of the
> > > +	  information returned by the uname() system call including
> > > +	  hostname, kernel version and domain name.
> > > +
> > > +	  This is used by container systems (e.g. vservers) so that
> > > +	  each container has its own hostname and other attributes.
> > > +	  Tasks in the container are placed in the UTS namespace
> > > +	  corresponding to the container.
> > 
> > this paragraph reads a little weird...  really what happens is that
> > each forked task is in the same UTS namespace as its parent, unless
> > it was cloned with CLONE_NEWUTS or has done unshare(CLONE_NEWUTS),
> > in which case it receives a copy.
> 
> You mean only the third paragraph, right? I hope the other two are
> accurate.
> 
> I'm trying to describe how the feature is used by container systems
> and my description is obviously inaccurate. There are subtle semantic
> differences between the way the different namespaces work, which you've
> pointed out. I think mentioning CLONE_NEWUTS or other flags is too
> technical for help descriptions.
> 
> For UTS_NS and IPC_NS I think I could remove that paragraph because
> the end user hint "Answer Y if you will be using a container system"
> remains. For USER_NS and PID_NS however, these features are tagged
> EXPERIMENTAL so the hint is "If unsure, say N" and I think I need
> to at least mention the use in container systems or find some better
> clarifying description which doesn't get too technical.
> 
> > > +	  This is used by container systems (e.g. vservers).
> > > +	  Tasks in the container are placed in the IPC namespace
> > > +	  corresponding to the container.
> > 
> > Same as with UTS, except that upon CLONE_NEWIPC the task receives a
> > blank new ipc namespace, not a copy of the original.
> 
> Per above my response is to remove the paragraph.
> 
> > >  config PID_NS
> > > [...]
> > >  	default n
> > >  	depends on NAMESPACES && EXPERIMENTAL
> > >  	help
> > > -	  Suport process id namespaces.  This allows having multiple
> > > -	  process with the same pid as long as they are in different
> > > -	  pid namespaces.  This is a building block of containers.
> > > +	  Enable experimental support for hierarchical process id namespaces.
> > > 
> > > -	  Unless you want to work with an experimental feature
> > > -	  say N here.
> > > +	  This is a function used by container-based virtualisation
> > > +	  systems (e.g. vservers).  Each process will have a distinct
> > > +	  Process ID in each PID namespace which the process is in.
> > > +	  Processes in the container are placed in the PID namespace
> > > +	  corresponding to the container, and cannot see or affect
> > > +	  processes in any parent PID namespace.
> > 
> > A cloned process inherits the pid namespace hierarchy from its
> > parent.  If it was cloned with CLONE_NEWPID, the hierarchy is
> > topped with one additional newly created pid namespace.  This
> > is the only pid namespace in which the new process will be able
> > to see processes, while it will be visible in all namespaces in
> > its pidns hierarchy.
> 
> Yes, I understand that. Would you agree that your problem is with the
> wording "Processes in the container are placed in the PID namespace
> corresponding to the container"? And that this is the part that needs
> to be fixed?

Yup.

thanks,
-serge

> ... todo = revisit these descriptions soon, not today though
> 
> Nick.
> -- 
> PGP Key ID = 0x418487E7                      http://www.nick-andrew.net/
> PGP Key fingerprint = B3ED 6894 8E49 1770 C24A  67E3 6266 6EB9 4184 87E7

      reply	other threads:[~2008-02-23  3:46 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-19 14:06 Improve init/Kconfig help descriptions [PATCH 0/9] Nick Andrew
2008-02-19 14:09 ` Improve init/Kconfig help descriptions [PATCH 1/9] Nick Andrew
2008-02-19 14:11 ` Improve init/Kconfig help descriptions [PATCH 2/9] Nick Andrew
2008-02-19 14:33 ` Improve init/Kconfig help descriptions [PATCH 3/9] Nick Andrew
2008-02-19 14:42   ` Pavel Emelyanov
2008-02-19 15:10     ` Nick Andrew
2008-02-19 15:16       ` Pavel Emelyanov
2008-02-19 15:50         ` Serge E. Hallyn
2008-02-19 16:44         ` Randy Dunlap
2008-02-19 22:41           ` Nick Andrew
2008-02-20 12:19           ` [PATCH 2.6.25-rc2 3/9] config: Improve init/Kconfig help descriptions - namespaces Nick Andrew
2008-02-20 12:23             ` Pavel Emelyanov
2008-02-20 13:01               ` Nick Andrew
2008-02-20 13:07                 ` Pavel Emelyanov
2008-02-20 16:50             ` serge
2008-02-20 23:10               ` Nick Andrew
2008-02-19 14:38 ` Improve init/Kconfig help descriptions [PATCH 4/9] Nick Andrew
2008-02-20  3:42   ` Valdis.Kletnieks
2008-02-20 22:17     ` Nick Andrew
2008-02-19 14:53 ` Improve init/Kconfig help descriptions [PATCH 5/9] Nick Andrew
2008-02-19 20:17   ` Randy Dunlap
2008-02-19 15:12 ` Improve init/Kconfig help descriptions [PATCH 6/9] Nick Andrew
2008-02-19 15:39   ` Paul Jackson
2008-02-20 12:41     ` Nick Andrew
2008-02-20 16:43       ` Paul Jackson
2008-02-20  2:04   ` Paul Menage
2008-02-20  2:54     ` Nick Andrew
2008-02-20  3:12       ` Paul Menage
2008-02-20 16:55       ` serge
2008-02-20 21:31         ` Nick Andrew
2008-02-19 15:15 ` Improve init/Kconfig help descriptions [PATCH 7/9] Nick Andrew
2008-02-19 15:21 ` Improve init/Kconfig help descriptions [PATCH 8/9] Nick Andrew
2008-02-19 15:27 ` Improve init/Kconfig help descriptions [PATCH 9/9] Nick Andrew
2008-02-20 22:33 ` [PATCH 2.6.25-rc2 1/9] init: Improve init/Kconfig help descriptions part 1 Nick Andrew
     [not found] ` <200802220014.m1M0Dh5r022354@rgminet03.oracle.com>
2008-02-22  0:19   ` [PATCH 2.6.25-rc2 5/9] Kconfig: Improve init/Kconfig help descriptions - IKCONFIG etc Randy Dunlap
2008-02-22  0:48 ` [PATCH 2.6.25-rc2 1/9] Kconfig: Improve init/Kconfig help descriptions part 1 Nick Andrew
2008-02-22  0:49 ` [PATCH 2.6.25-rc2 2/9] Kconfig: Improve init/Kconfig help descriptions - TASKSTATS Nick Andrew
2008-02-22  0:51 ` [PATCH 2.6.25-rc2 3/9] Kconfig: Improve init/Kconfig help descriptions - NAMESPACES Nick Andrew
2008-02-27 23:00   ` Nick Andrew
2008-02-27 23:08     ` Serge E. Hallyn
2008-02-22  0:52 ` [PATCH 2.6.25-rc2 4/9] Kconfig: Improve init/Kconfig help descriptions - AUDIT Nick Andrew
2008-02-22  0:54 ` [PATCH 2.6.25-rc2 5/9] Kconfig: Improve init/Kconfig help descriptions - IKCONFIG etc Nick Andrew
2008-02-22  0:55 ` [PATCH 2.6.25-rc2 6/9] Kconfig: Improve init/Kconfig help descriptions - CGROUPS Nick Andrew
2008-02-22  0:56 ` [PATCH 2.6.25-rc2 7/9] Kconfig: Improve init/Kconfig help descriptions - EMBEDDED etc Nick Andrew
2008-02-22  0:58 ` [PATCH 2.6.25-rc2 8/9] Kconfig: Improve init/Kconfig help descriptions - SLAB Nick Andrew
2008-02-22  0:59 ` [PATCH 2.6.25-rc2 9/9] Kconfig: Improve init/Kconfig help descriptions - MODULES Nick Andrew
     [not found] ` <200802220010.m1M0Arr7024044@vzorg.swsoft.net>
2008-02-22  8:14   ` [PATCH 2.6.25-rc2 3/9] Kconfig: Improve init/Kconfig help descriptions - NAMESPACES Pavel Emelyanov
     [not found] ` <200802220010.m1M0Auqn024414@e5.ny.us.ibm.com>
2008-02-22 22:14   ` Serge E. Hallyn
2008-02-23  1:12     ` Nick Andrew
2008-02-23  3:45       ` Serge E. Hallyn [this message]

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