linux-kernel - Re: CLONE_NEWUTS documentation

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Message-ID: <20081123224708.GC12687@hallyn.com>
Date:	Sun, 23 Nov 2008 16:47:08 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Michael Kerrisk <mtk.manpages@...glemail.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>, linux-man@...r.kernel.org,
	Kirill Korotaev <dev@...nvz.org>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Andrey Savochkin <saw@...ru>,
	Subrata Modak <subrata@...ux.vnet.ibm.com>
Subject: Re: CLONE_NEWUTS documentation

Quoting Michael Kerrisk (mtk.manpages@...glemail.com):
> Serge, Eric,
> 
> Below is a patch to document the CLONE_NEWUTS flag that was
> added in 2.6.19.

Thanks for writing this.

> Could you please review and let me know of improvements
> or inaccuracies?
> 
> By the way, does anyone know where the UTS name in the uname()
> API comes from? My best guess is that it's from Unix Timesharing
> System, but I don't know this for sure.

That sounds plausible - I've wondered myself and even googled a
bit, but not found an answer.  I suppose we might need to ask
Linus, or check one of the git repos that goes back to the early
90s and see who created the struct.

> Cheers,
> 
> Michael
> 
> diff --git a/man2/clone.2 b/man2/clone.2
> index 7212332..80f9caf 100644
> --- a/man2/clone.2
> +++ b/man2/clone.2
> @@ -341,6 +340,33 @@ configuration option and that the process be privileged
>  This flag can't be specified in conjunction with
>  .BR CLONE_THREAD .
>  .TP
> +.BR CLONE_NEWUTS " (since Linux 2.6.19)"
> +If
> +.B CLONE_NEWUTS
> +is set, then create the process in a new UTS namespace.

And the new UTS namespace will initially be identical as the
parent - same hostname and domainname.

> +If this flag is not set, then (as with
> +.BR fork (2)),
> +the process is created in the same UTS namespace as
> +the calling process.
> +This flag is intended for the implementation of control groups.

I'm not sure Eric was sufficiently clear - this flag is intended
for the implementation of virtual server functionality and maybe
checkpoint/restart (though I'm not sure any apps will care about
being able to reset the hostname on restart :)

It's not that you have to call it 'virtual server functionality',
just that 'control groups' is definately not right.

Maybe 'lightweight containers'?  "lightweight virtual servers'?

thanks,
-serge
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