Date: Wed, 27 Feb 2008 17:08:36 -0600
From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Nick Andrew <nick@nick-andrew.net>
Cc: trivial@kernel.org, linux-kernel@vger.kernel.org,
       Serge Hallyn <serue@us.ibm.com>, Randy Dunlap <randy.dunlap@oracle.com>,
       Paul Menage <menage@google.com>, Paul Jackson <pj@sgi.com>,
       Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
       Pavel Emelyanov <xemul@openvz.org>
Subject: Re: [PATCH 2.6.25-rc2 3/9] Kconfig: Improve init/Kconfig help
	descriptions - NAMESPACES
Message-ID: <20080227230836.GA3296@sergelap.austin.ibm.com>
References: <20080222-114832-init-kconfig-3@tull.net> <20080227225949.16087.31336.stgit@marcab.local.tull.net>
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Quoting Nick Andrew (nick@nick-andrew.net):
> Modify the help descriptions of init/Kconfig for clarity, accuracy and consistency.
> 
> Kernel config options affected:
> 
>   - NAMESPACES
>   - UTS_NS
>   - IPC_NS
>   - USER_NS
>   - PID_NS
> 
> Add a brief description of what namespaces are and when you would
> want to use them.
> 
> For the *_NS options, add a tiny bit of detail about what it is,
> and ensure each config option has an answer hint: Y for namespaces
> "if you will be using a container system", Y for the *_NS options
> except for the two labeled EXPERIMENTAL.
> 
> Signed-off-by: Nick Andrew <nick@nick-andrew.net>

Thanks, Nick.

Acked-by: Serge Hallyn <serue@us.ibm.com>

-serge

> ---
> Try #4
> 
> 
>  init/Kconfig |   65 +++++++++++++++++++++++++++++++++++++++++++++-------------
>  1 files changed, 50 insertions(+), 15 deletions(-)
> 
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index cc7a341..0e6a084 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -487,31 +487,62 @@ config NAMESPACES
>  	bool "Namespaces support" if EMBEDDED
>  	default !EMBEDDED
>  	help
> -	  Provides the way to make tasks work with different objects using
> -	  the same id. For example same IPC id may refer to different objects
> -	  or same user id or pid may refer to different tasks when used in
> -	  different namespaces.
> +	  Select various namespace options.
> +
> +	  Namespaces allow different kernel objects (such as processes
> +	  or sockets) to have the same ID in different namespaces.
> +	  Identifiers like process IDs, which historically were globally
> +	  unique, will now be unique only within each PID namespace.
> +	  Each task can refer only to PIDs within the same namespace
> +	  as the task itself.
> +
> +	  Namespaces are used by container systems (e.g. vservers)
> +	  to provide isolation between the containers.
> +
> +	  This option does not affect any kernel code directly; it merely
> +	  allows you to select namespace options below.
> +
> +	  Answer Y if you will be using a container system, and you
> +	  will probably want to enable all the namespace options
> +	  below.
> 
>  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.
> +
> +	  Answer Y if you will be using a container system.
> 
>  config IPC_NS
>  	bool "IPC namespace"
>  	depends on NAMESPACES && SYSVIPC
>  	help
> -	  In this namespace tasks work with IPC ids which correspond to
> -	  different IPC objects in different namespaces
> +	  Enable support for namespace-specific IPC IDs.
> +
> +	  IPC IDs will be unique only within each IPC namespace.
> +
> +	  Answer Y if you will be using a container system.
> 
>  config USER_NS
>  	bool "User namespace (EXPERIMENTAL)"
>  	depends on NAMESPACES && EXPERIMENTAL
>  	help
> -	  This allows containers, i.e. vservers, to use user namespaces
> -	  to provide different user info for different servers.
> +	  Enable experimental support for user namespaces.
> +
> +	  This is a function used by container-based virtualisation systems
> +	  (e.g. vservers). User namespaces are intended to ensure that
> +	  processes with the same uid which are in different containers are
> +	  isolated from each other.
> +
> +	  Currently user namespaces provide separate accounting, while
> +	  isolation must be provided using SELinux or a custom security
> +	  module.
> +
>  	  If unsure, say N.
> 
>  config PID_NS
> @@ -519,12 +550,16 @@ 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.
> +
> +	  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.
> +	  A process can "see" other processes in the same PID namespace
> +	  and child PID namespaces, but cannot see processes in parent
> +	  PID namespaces.
> 
> -	  Unless you want to work with an experimental feature
> -	  say N here.
> +	  If unsure, say N.
> 
>  config BLK_DEV_INITRD
>  	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
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