From owner-freebsd-fs@freebsd.org  Sun Nov  4 16:58:50 2018
Return-Path: <owner-freebsd-fs@freebsd.org>
Delivered-To: freebsd-fs@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2E1E810DCC55
 for <freebsd-fs@mailman.ysv.freebsd.org>; Sun,  4 Nov 2018 16:58:50 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 4A28479EE1;
 Sun,  4 Nov 2018 16:58:49 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from tom.home (kib@localhost [127.0.0.1])
 by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id wA4GwcWs004587
 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);
 Sun, 4 Nov 2018 18:58:41 +0200 (EET)
 (envelope-from kostikbel@gmail.com)
DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua wA4GwcWs004587
Received: (from kostik@localhost)
 by tom.home (8.15.2/8.15.2/Submit) id wA4Gwc3E004586;
 Sun, 4 Nov 2018 18:58:38 +0200 (EET)
 (envelope-from kostikbel@gmail.com)
X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com
 using -f
Date: Sun, 4 Nov 2018 18:58:38 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Rick Macklem <rmacklem@uoguelph.ca>
Cc: Julian Elischer <julian@freebsd.org>, Andriy Gapon <avg@FreeBSD.org>,
 FreeBSD Filesystems <freebsd-fs@freebsd.org>
Subject: Re: How to fill in the fsid for file systems?
Message-ID: <20181104165838.GA5335@kib.kiev.ua>
References: <YTOPR0101MB11620BAF0E206EE36E927A5ADDF30@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
 <20181030012240.GM5335@kib.kiev.ua>
 <YTOPR0101MB11621427AF47133A93311E16DDCD0@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
 <e7813a64-59c2-67a1-3471-b32a6ca42ef8@FreeBSD.org>
 <YTOPR0101MB116207BA89FB66EE9B1AAF01DDCD0@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
 <a831d660-1ed9-ef21-f457-8e1e986b96f2@FreeBSD.org>
 <YTOPR0101MB11621C0D5F4F4D9BED169110DDCF0@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
 <c98b999c-c4b8-55fe-adef-ac53e439487b@freebsd.org>
 <YTOPR0101MB1162A8CA4B3AAF230E73158DDDC90@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
 <YTOPR0101MB11625B448278C5FAA1625772DDC90@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YTOPR0101MB11625B448278C5FAA1625772DDC90@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>
User-Agent: Mutt/1.10.1 (2018-07-13)
X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00,
 DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM,
 NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.2
X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on tom.home
X-Rspamd-Queue-Id: 4A28479EE1
X-Spamd-Result: default: False [-1.33 / 200.00]; ARC_NA(0.00)[];
 FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4];
 FREEMAIL_FROM(0.00)[gmail.com]; MIME_GOOD(-0.10)[text/plain];
 HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all];
 RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[];
 TO_DN_ALL(0.00)[];
 MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com];
 NEURAL_HAM_SHORT(-0.98)[-0.977,0];
 IP_SCORE(-1.34)[ipnet: 2001:470::/32(-3.57), asn: 6939(-3.08), country:
 US(-0.07)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[];
 SUBJECT_ENDS_QUESTION(1.00)[];
 ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US];
 RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com];
 DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none]
X-Rspamd-Server: mx1.freebsd.org
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs/>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 04 Nov 2018 16:58:50 -0000

On Sun, Nov 04, 2018 at 03:47:16PM +0000, Rick Macklem wrote:
> Oh, and I am not sure what happens w.r.t. the fsid for UFS snapshots?

Superblock for the snapshot is the verbatim copy of the superblock for
the actual UFS volume.  As the consequence, their fsids are same.

You cannot quite substitute the real export by a snapshot export, because
snapshot is read-only.  But if it is fine, equal fsids are also fine.