Date: Mon, 11 Jun 2007 20:17:14 -0400 From: Bill Moran <wmoran@potentialtech.com> To: Modulok <modulok@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: umount -f Message-ID: <20070611201714.35153d92.wmoran@potentialtech.com> In-Reply-To: <64c038660706111652p311c6d84i1ec295edcfc16994@mail.gmail.com> References: <64c038660706111652p311c6d84i1ec295edcfc16994@mail.gmail.com>
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Modulok <modulok@gmail.com> wrote: > > Couple questions for anyone on the list who has a moment (and the answer to > any of these): > > Objective: I need to kick people off of a storage drive (we'll say > /dev/ad4), without corrupting the file system and without bringing the > entire system down. I need to safely umount the file systems, even if my > users have processes which have files open. > > 1. If I use "umount -f /dev/ad4s1a" to forcefully umount a file system, does > this jeopardize the integrity of said file system? Like...will it jerk the > run out from under a process in the middle of a disk write, thus leaving a > half written file, or will it wait until the write is complete? (I guess > this would largely depend on the disk controller?) I don't believe there are any guarantees if your -f it. The filesystem will probably be OK, but I would expect files to get corrupt. > 2. How do I get a list of processes that are accessing a specific file > system, e.g. /dev/ad4s1a? fstat(1) is your friend. > 3. Is there any safe way to unconditionally umount a file system, even if a > run-away process is writing to it (as bad of an idea as this is)? I would write a script that pulls fstat data, then kills any processes with files open, then attempts to unmount the filesystem. If that fails, go through the fstat data again and kill -9 the processes this time. If all that fails, you can finally choose to umount -f. You could also try some looping constructs, kill/umount four or five times before switching to kill -9/umount, etc. It all depends on how desperate you are to get the filesystem unmounted, how long you're willing to wait, how much data you're willing to lose, etc. -- Bill Moran http://www.potentialtech.com
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