Date: Sun, 10 Feb 2002 10:20:44 -0600 From: "Guy Helmer" <ghelmer@palisadesys.com> To: "'BOUWSMA Beery'" <freebsd-user@netscum.dyndns.dk>, <hackers@FreeBSD.ORG> Subject: RE: nullfs and unionfs Message-ID: <000001c1b24e$ffacea40$0200000a@spencer> In-Reply-To: <200112200108.fBK18fJ00337@crotchety.newsbastards.org>
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On Wednesday, December 19, 2001 7:09 PM BOUWSMA Beery wrote: > > Is it safe (relatively speaking) to use the null and the union > filesystems? The LINT kernel config file still includes dire > warnings, as do the man pages, but so far I've successfully > mounted a handful of filesystems without panicking my system, > though I've been careful to do it read-only when possible > ... > I do this by keeping the actual source read-write for cvsup > in /usr/local/system, which I then mount_null read-only on > /usr/src. (Likewise ports and stuff) > > Over top of this nullfs /usr/src I mount read-write my own > directory which gets my changes in /usr/local/source-hacks. It looks like there are still some serious problems with this. I just tried a similar thing on FreeBSD 4.4 and 4.5. I created a directory of binaries to use for multiple jails, then null-mounted (read-only) the binaries for each of the jails to use. To allow the /etc and other parts of the jails to be written, I union-mounted a per-jail writeable filesystem over each of the null mounts. It seemed to work well until my jail setup program actually started a binary from inside the jail (i.e., from the null mount) when the kernel panic'ed with trap 12. Guy Helmer Palisade Systems, Inc. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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