From: Autif Khan Subject: How can I flush all writes before yanking the power cable? Date: Thu, 7 Feb 2013 11:43:23 -0500 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: linux-ext4@vger.kernel.org Return-path: Received: from mail-lb0-f178.google.com ([209.85.217.178]:40794 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757884Ab3BGQnY (ORCPT ); Thu, 7 Feb 2013 11:43:24 -0500 Received: by mail-lb0-f178.google.com with SMTP id n1so2292750lba.9 for ; Thu, 07 Feb 2013 08:43:23 -0800 (PST) Sender: linux-ext4-owner@vger.kernel.org List-ID: The standard operating procedure to power down my machine is to switch it off. To work around this, we use mSATA SSDs (actually we recently switched from SATA SSDs) with linux on a read only partition. This works just fine, however, we want to be able to upgrade some parts of the application. To do this, we have put the application on /app partition. We mount it read only at start up. When we want to upgrade the app, we remount read-write sync (mount -o remount,rw,sync /app) perform the write operations and remount read only. If we yank the power cable after this, we get file system errors on the next reboot. We can display a message to the user telling them that it is safe to power down the machine. My question is 1) Is this the right place to discuss this or should I have posted this in the file systems mailing list? 2) how can we determine that all the writes are flushed? (and this it is safe to yank the power cable) 3) is there a better way to do this? - for example we may not have to remount read write sync - and we can force a sync before remounting read only or something I have already tried "sudo sync" before remounting the filesystem as read only. It does not help. Please advise. Thanks Autif