From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 17 Aug 2001 04:19:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 17 Aug 2001 04:18:56 -0400 Received: from smtpde02.sap-ag.de ([194.39.131.53]:2201 "EHLO smtpde02.sap-ag.de") by vger.kernel.org with ESMTP id ; Fri, 17 Aug 2001 04:18:42 -0400 From: Christoph Rohland To: safemode Cc: linux-kernel@vger.kernel.org Subject: Re: question about tmpfs In-Reply-To: <20010817064809Z269735-760+2777@vger.kernel.org> Organisation: SAP LinuxLab Date: 17 Aug 2001 10:18:46 +0200 In-Reply-To: <20010817064809Z269735-760+2777@vger.kernel.org> Message-ID: User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.1 (Cuyahoga Valley) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SAP: out X-SAP: out Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 17 Aug 2001, safemode@speakeasy.net wrote: > I looked in the documentation for something about tmpfs and looked > around for some obvious tmpfs source but couldn't find any to figure > out how to know when/if it's doing what it's supposed to. when i ls > the dir it's mounted to i get nothing and this is what df gives me. > Filesystem 1k-blocks Used Available Use% Mounted on > tmpfs 144108 0 144108 0% /dev/shm In the 2.3 timeframe SYSV shared memory did require you to mount shmfs somewhere to work properly. This was relaxed since Al Viro introduced kernel internal mount points. This feature is used now for SYSV shm and shared anonymous maps. You do not see this instance in user space. You can use ipcs to show the SYSV segmants. The instance on /dev/shm only used by the shmopen/shmunlink functions of glibc 2.2. These functions are specified by POSIX for shared memory handling. Since there aren't a lot of programs using this interface right now, you do not see anything here and could drop this mount from your fstab. But if you use such a program you will need a tmpfs instance mounted somewhere (preferably under /dev/shm). Greetings Christoph