Date: Tue, 04 Apr 2000 12:36:22 -0600 From: Warner Losh <imp@village.org> To: "Jeffrey S. Sharp" <jss@subatomix.com> Cc: "freebsd-small" <freebsd-small@FreeBSD.ORG> Subject: Re: Mounting and Corruption Rehashed Message-ID: <200004041836.MAA70239@harmony.village.org> In-Reply-To: Your message of "Tue, 04 Apr 2000 14:16:05 CDT." <001f01bf9e6a$3a0b3c00$2aa85c0a@vulcan> References: <001f01bf9e6a$3a0b3c00$2aa85c0a@vulcan>
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In message <001f01bf9e6a$3a0b3c00$2aa85c0a@vulcan> "Jeffrey S. Sharp" writes: : Let's set the way-back knob to a few months ago. We were discussing the : viability of doing the following: : : * Mounting flash read-only on / : * Mounting small MFS filesystems on /var and /tmp : * Temporarily remounting / read-write to make changes : : The problem was this little paragraph from `man mount`: : : > Switching a filesystem back and forth between asynchronous : > and normal operation or between read/write and read/only : > access using ``mount -u'' may gradually bring about severe : > filesystem corruption. : : Someone spoke up and said that they had actually experienced this : corruption. I've not seen corruption. However, I oly change one or two files somewhat infrequently and tend to reboot often when I'm changing the underlying filesystem. : Please excuse me if the following is a dumb question: why even mount the : flash _read-only_ in the first place? If /var and /tmp are on separate : filesystems (MFS), what write operations are going to happen to the flash : that mounting read-only would prevent? The superblock gets updated from time to time. Also, when things are mounted r/o you can power off at any time and know that the filesystem will be stable when you come back. I've had some problems in the past where I've trashed a filesystem that was mounted r/w by doing this at just the wrong time even though there wasn't much activity. Mounting R/O ensures that you don't accidentally do writes as well. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-small" in the body of the message
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