From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.jrs-s.net ([173.230.137.22]:47754 "EHLO mail.jrs-s.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751281AbaAESJf (ORCPT ); Sun, 5 Jan 2014 13:09:35 -0500 Message-ID: <52C99FDD.4090709@jrs-s.net> Date: Sun, 05 Jan 2014 13:09:33 -0500 From: Jim Salter MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org, "dhan.war" Subject: Re: how to properly mount an external usb hard drive & other questions References: <52C8E0D1.2070904@gmail.com> <52C999D2.4000006@dergleichrichter.de> <52C99B76.2020604@dergleichrichter.de> <52C99E19.8020106@jrs-s.net> In-Reply-To: <52C99E19.8020106@jrs-s.net> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 01/05/2014 01:02 PM, Jim Salter wrote: > If you want LZO compression, as you specified: > > /dev/sdc /path/to/mountpoint compress=lzo,noauto,users,user 0 0 > > Better yet, if your btrfs is actually on /dev/sdc right now, let's get > that fstab entry mounting it by UUID instead. > > ls -l /dev/disk/by-uuid | grep sdc > lrwxrwxrwx 1 root root 10 Jan 3 09:40 > 12345678-9abc0-1234-5678-9a0123456789 -> ../../sdc > > So then: > > # this is not a real UUID, you need to check > /dev/disk/by-uuid on your machine for a real UUID > UUID=12345678-9abc0-1234-5678-9a0123456789 > /path/to/mountpoint compress=lzo,noauto,users,user 0 0 > > This is EXTRA important with a USB drive, since it's HIGHLY likely it > won't always be on the same physical devicename. One other note: in this particular case, you might actually be better served setting compression by mounting the drive normally, then: cd /path/to/drive chattr +c . ; chattr +c * ; chattr +c .* This will set compression on by default for any future files stored on that USB drive, *without* needing any special mount options. Why might this be a better idea? Well, if it's a USB drive, presumably you might want to mount it on foreign systems from time to time. This way, even if you mount the drive on a foreign system that doesn't know anything about your preferences, it will see the +c on the root directory of the drive, and store any new data on the drive compressed. The only caveat: +c won't set the compression algorithm to LZO. It'll be gzip, which is the default algorithm. (And, of course, this won't compress any EXISTING data already stored there - only NEW data written to it after you set the +c attribute.)