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Date: Wed, 20 Feb 2008 23:19:15 +1100 From: Nick Andrew <nick@...k-andrew.net> To: Randy Dunlap <randy.dunlap@...cle.com> Cc: Pavel Emelyanov <xemul@...nvz.org>, trivial@...nel.org, linux-kernel@...r.kernel.org, Serge Hallyn <serue@...ibm.com> Subject: [PATCH 2.6.25-rc2 3/9] config: Improve init/Kconfig help descriptions - namespaces Rewrite the help descriptions for clarity, accuracy and consistency. Kernel config options affected: - NAMESPACES - UTS_NS - IPC_NS - USER_NS - PID_NS Signed-off-by: Nick Andrew <nick@...k-andrew.net> --- Here's try #2 at the 3rd patch in the series, for namespace descriptions. Patching against Linus' git tree now, and trying to comply with the standards for submitting patches. Each of the UTS/IPC/USER/PID descriptions is subtly different, but I hope they all are clear and accurate. --- a/init/Kconfig 2008-02-20 09:34:48.000000000 +1100 +++ b/init/Kconfig 2008-02-20 22:55:41.000000000 +1100 @@ -414,31 +414,71 @@ 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 (i.e. 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. + + This is used by container systems (i.e. 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. + + 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. + + This is used by container systems (i.e. vservers). + Tasks in the container are placed in the IPC namespace + corresponding to the container. + + 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 @@ -446,12 +486,20 @@ 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. + Process IDs will be unique only within each PID namespace. + This allows multiple processes to have the same PID + so long as they are in different PID namespaces. Furthermore, + each process will have a distinct PID in each namespace + the process is in. + + This is used by container systems (i.e. vservers). + Tasks in the container are placed in the PID namespace + corresponding to the container, and can only see or + affect processes in the same PID namespace. + + If unsure, say N. config BLK_DEV_INITRD bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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