From owner-freebsd-questions Thu Mar 25 22: 9:51 1999 Delivered-To: freebsd-questions@freebsd.org Received: from cc942873-a.ewndsr1.nj.home.com (cc942873-a.ewndsr1.nj.home.com [24.2.89.207]) by hub.freebsd.org (Postfix) with ESMTP id 965E214F2C for ; Thu, 25 Mar 1999 22:09:42 -0800 (PST) (envelope-from cjc@cc942873-a.ewndsr1.nj.home.com) Received: (from cjc@localhost) by cc942873-a.ewndsr1.nj.home.com (8.9.3/8.8.8) id BAA17991; Fri, 26 Mar 1999 01:09:29 -0500 (EST) (envelope-from cjc) From: "Crist J. Clark" Message-Id: <199903260609.BAA17991@cc942873-a.ewndsr1.nj.home.com> Subject: Re: "dump" of a "live" file system? In-Reply-To: from Evgeny Roubinchtein at "Mar 25, 99 09:10:42 pm" To: eroubinc@u.washington.edu (Evgeny Roubinchtein) Date: Fri, 26 Mar 1999 01:09:29 -0500 (EST) Cc: freebsd-questions@FreeBSD.ORG Reply-To: cjclark@home.com X-Mailer: ELM [version 2.4ME+ PL40 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Evgeny Roubinchtein wrote, > > Is it possible to "dump" a "live" file system? (i.e. dump a file system > when the machine is in multi-user mode, with the filesystem that is being > dumped mounted read-write). Is it safe/recommended? It is pretty much assumed most backups are done from live (rw) disks. I always use dump(1) on all of my different UNIX machines (some with spiffy wrappers around it, though). I have gotten warning messages about files changing size duriung a dump, but I have yet to have it cause any real problem. > It seems like this wouldn't be a great idea, since on a "live" file system > mounted read-write there may be pending writes, and it isn't clear how > dump would cope with that. Is it better/ok/safe to first remount the > filesystem read-only? This is simply not an option for any production machine. Any backup program has to be ready for this. It is not necessarily possible to take a 'snap-shot' of a disk. Your idea of unmounting the disk would create lots of problems on its own. How do you get users to stop writing or trying to write? When you 'umount -f' the filesystem, what might that break? etc. Of course, people tend to do backups during periods of relative inactivity in teh first place. This is often done since the process taxes system resources, but less user disk usage is an equally if not more significant reason not to. -- Crist J. Clark cjclark@home.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message