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From: Michael Kerrisk <>
To: "Eric W. Biederman" <>
Cc: Kirill Korotaev <>,
	lkml <>,
	Pavel Emelianov <>,
	Cedric Le Goater <>
Subject: Re: CLONE_NEWIPC documentation
Date: Mon, 06 Aug 2007 08:36:45 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Eric W. Biederman wrote:
> Michael Kerrisk <> writes:
>> Hello Kirill,
>> In 2.6.19, your patch to add support for CLONE_NEWIPC was included.  Is
>> there there some for-userland-programmers documentation of this flag
>> somewhere?  Would you be able to send some documentation to me (ideally as
>> a patch to the clone.2 man page, but otherwise some plain text will do).
>> If this flag is also supported for unshare(), then could you please send me
>> a patch/text for that too?
> In case someone else doesn't do better here is a short summary.

Thanks Eric.  That looks to cover a lot of the essentials.  Anyone else see
something important that should be documented?

And a further question: is CLONE_NEWIPC implemented for unshare()?



> CLONE_NEWIPC creates a new ipc namespace for the new child and all
> of it's children.  So far CAP_SYS_ADMIN is required.
> An IPC namespace creates a new context for looking up and listing
> SYSV IPC shared memory, message queues, and semaphores.  Only allowing
> finding of SYSV IPC objects in this namespace.
> For most practical purposes two processes in different SYSV IPC
> namespaces might as well be on different machines.  As they cannot
> find each others SYSV IPC resources, and so cannot interact with
> each other that way.
> The implementation is essentially just a lookup of the objects
> in a different table when doing name to object translation so
> there should be no measurable overhead.
> When the last process in a SYSV IPC namespace exits any remaining
> objects in that SYSV IPC namespace are destroyed.
> Eric

Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7

Want to help with man page maintenance?  Grab the latest tarball at
read the HOWTOHELP file and grep the source files for 'FIXME'.

  reply	other threads:[~2007-08-06  6:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-05  9:35 Michael Kerrisk
2007-08-05 12:24 ` Eric W. Biederman
2007-08-06  6:36   ` Michael Kerrisk [this message]
2008-11-19 19:12 Michael Kerrisk
2008-11-20  1:16 ` Eric W. Biederman
2008-11-20  8:36   ` Cedric Le Goater
2008-11-20 11:28     ` Michael Kerrisk
2008-11-20 12:26       ` Cedric Le Goater
2008-11-20 16:28         ` Michael Kerrisk
2008-11-23 22:48   ` Serge E. Hallyn

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