From owner-freebsd-questions@freebsd.org Thu Apr 13 09:03:13 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 4C4C8D3AE30 for ; Thu, 13 Apr 2017 09:03:13 +0000 (UTC) (envelope-from tech-lists@zyxst.net) Received: from out1-smtp.messagingengine.com (out1-smtp.messagingengine.com [66.111.4.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 207ACC85 for ; Thu, 13 Apr 2017 09:03:12 +0000 (UTC) (envelope-from tech-lists@zyxst.net) Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.nyi.internal (Postfix) with ESMTP id DC49420EA8 for ; Thu, 13 Apr 2017 05:03:05 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute4.internal (MEProxy); Thu, 13 Apr 2017 05:03:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zyxst.net; h= content-transfer-encoding:content-type:date:from:message-id :mime-version:subject:to:x-me-sender:x-me-sender:x-sasl-enc :x-sasl-enc; s=fm1; bh=cJCced/+HeLH8XiSLaFzFWbpWFFRZ0Use6fHyIC35 GA=; b=seOaul+HVFW00T3b52DGqqfCPnvQ4F/9LWs/Ipyb8P1t6mdum9CehGAfW SA6ygfL5e7geuwF0zjH0mfIEDIvtNXxUmzuE445gT9RvVlNk0bbitnPq86ezZuqa 8yzd827afS91DrgSy0UEqvYJV1pmiFaa0Kwdo7ELczg7EzKpPXXHFkLaqd4YSo29 rzLUhyE4IRA5wHZr5g6SkNwv64Tjkie83UTlH5Wpj4GUQPZE2Zb1YmatoEYpRcov iI/Rrtc/6ggmVt4rQHNk4SUXL+BLV9H6BNKXgjQJ2NZH+HqmPZMTnEJJPcnpUgGw kNg0QIL4vtf54kqlwhaLsa9YwaUTw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-sender :x-me-sender:x-sasl-enc:x-sasl-enc; s=fm1; bh=cJCced/+HeLH8XiSLa FzFWbpWFFRZ0Use6fHyIC35GA=; b=U5i+7SMjagiFSM1SBvi321kfRpJePIrc5N oMMwifLEoq65YFFF6eA9HTWbBpjwMkS6I+hhirA3/6Sy3cSkC/+cJlmnyh0TieDH qneVyMa6rlzvhMKyUs5s07f+xM6uwelWBa6GLuD9Aximo1WNCDcoHF+EqsOZGWz4 SE41uVKWB91wfmxyy6LADMdkjDEQuM/s7q0WuP9hATP0wkVjdnxV/KlnTmlgAUMd bUtN6wiQeb6jGKL2y0JnZmCbNFiN90qcXwfb7fA2LYdlpsnvtKWoA3cyu6PqJsPV /uemr4dT9yTjzvooIi67wKwlF6NxW5Mjz0jujfEwCG3YIPk1wEqQ== X-ME-Sender: X-Sasl-enc: mMnNXTUDsPGpwO265l8sXVNCzuLKxPHmgE9Oi0N0j7IZ 1492074185 Received: from pumpkin.growveg.org (pumpkin.growveg.org [82.70.91.101]) by mail.messagingengine.com (Postfix) with ESMTPA id 8231724346 for ; Thu, 13 Apr 2017 05:03:05 -0400 (EDT) To: freebsd-questions@freebsd.org From: tech-lists Subject: hopefully simple query regarding dd Message-ID: <7ed0944d-56d0-fc10-629b-b90067f48651@zyxst.net> Date: Thu, 13 Apr 2017 10:03:02 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:52.0) Gecko/20100101 Thunderbird/52.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Apr 2017 09:03:13 -0000 Hello questions@ I couldn't find an an answer to this hopefully non-silly question and can't test it meself without possibly risking a hd. Basically what I want to know is this. Can I do this: dd if=/dev/ada0 of=/dev/ada0 to refresh the disk, and *expect the outcome to be non-destructive for the disk*. That bit is important. By non-destructive, I mean for the data already on it. Can I do this multiuser or do I need to boot to a rescue environment beforehand? thanks, -- J.