From owner-freebsd-questions@FreeBSD.ORG Sat May 24 15:41:07 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id B8FFF90D for ; Sat, 24 May 2014 15:41:07 +0000 (UTC) Received: from mx01.qsc.de (mx01.qsc.de [213.148.129.14]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7B12C257D for ; Sat, 24 May 2014 15:41:07 +0000 (UTC) Received: from r56.edvax.de (port-92-195-4-63.dynamic.qsc.de [92.195.4.63]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx01.qsc.de (Postfix) with ESMTPS id 7BE3B3CBE6; Sat, 24 May 2014 17:41:03 +0200 (CEST) Received: from r56.edvax.de (localhost [127.0.0.1]) by r56.edvax.de (8.14.5/8.14.5) with SMTP id s4OFf33E004785; Sat, 24 May 2014 17:41:03 +0200 (CEST) (envelope-from freebsd@edvax.de) Date: Sat, 24 May 2014 17:41:02 +0200 From: Polytropon To: Arthur Chance Subject: Re: write-protected usb flash drive Message-Id: <20140524174102.66eff3da.freebsd@edvax.de> In-Reply-To: <5380B953.5090700@qeng-ho.org> References: <537FE744.3030002@dreamchaser.org> <20140524080127.f2e788d5.freebsd@edvax.de> <5380AB17.2070300@dreamchaser.org> <5380B953.5090700@qeng-ho.org> Reply-To: Polytropon Organization: EDVAX X-Mailer: Sylpheed 3.1.1 (GTK+ 2.24.5; i386-portbld-freebsd8.2) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: FreeBSD Mailing List X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 24 May 2014 15:41:07 -0000 On Sat, 24 May 2014 16:22:59 +0100, Arthur Chance wrote: > OK, thought I'd better try my own advice rather than just handing it > out. I put a microSD card out of an old phone into a SanDisk mSD -> SD > adapter and plugged that into my SanDisk SD -> USB adapter, mounted it > (FAT32 file system already on it) and wrote a file to it. Worked as > you'd expect. I then unmounted and unplugged it, flipped the write > protect switch and tried to remount. Result was > > mount_msdosfs: /dev/da5s1: Input/output error > > Mounting it read-only was fine. So, the write protect is honoured by at > least some SD -> USB adapters. This is already on file system level. It _should_ work the same at upper layers, for example when using dd to write NULs to the device with the write protection on - an error should (correctly) occur in that case. When a r/o mount is forced, the routines accessing that file system cannot avoid the write protection. Still writes are possible _aside of_ the file system which should be prevented by the switch as well. It's probably a good idea to check that too, e. g. put in the card with write protection on and then try dd or newfs on it. -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...