From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-02.dd24.net ([193.46.215.43]:50348 "EHLO mailgw-02.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444AbbLIEgm (ORCPT ); Tue, 8 Dec 2015 23:36:42 -0500 Message-ID: <1449635797.20578.0.camel@scientia.net> Subject: Re: subvols and parents - how? From: Christoph Anton Mitterer To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org Date: Wed, 09 Dec 2015 05:36:37 +0100 In-Reply-To: References: <1448340960.14125.51.camel@scientia.net> <1448400350.21291.88.camel@scientia.net> Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-878GXYsMU839CRJLEMRp" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-878GXYsMU839CRJLEMRp Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2015-11-27 at 01:02 +0000, Duncan wrote: [snip snap] > #1 could be a pain to setup if you weren't actually mounting it > previously, just relying on the nested tree, AND... >=20 > #2 The point I was trying to make, now, to mount it you'll mount not > a=20 > native nested subvol, and not a directly available sibling > 5/subvols/home, but you'll actually be reaching into an entirely=20 > different nesting structure to grab something down inside, mounting > 5/subvols/root/home subvolume nesting down inside the direct > 5/subvols/root sibling subvol. Okay so your main point was basically "keeping things administrable"... > one of which was that everything=20 > that the package manager installs should be on the same partition > with=20 > the installed-package database, so if it has to be restored from > backup,=20 > at least if it's all old, at least it's all equally old, and the > package=20 > database actually matches what's on the system because it's in the > same=20 > backup! I basically agree, though I'd allow few exceptions, like database-like data that is stored in /var/ sometimes and that doesn't need to be consistent with anything but iself... e.g. static web pages (/var/www)... postgresl DB, or sks keyserver DB... and so on. btw: What's the proper way for merging / splitting into subvols. E.g. consider I have: 5 | +--root (subvol) =C2=A0 =C2=A0| =C2=A0 =C2=A0+-- var (no subvol) And say I would want to split of var/www into a subvol. Well one obvious way would be with mv (and AFAIU that would keep my ref-links with clones, if any) but that also means that anything that accesses /var/www probably needs a downtime. Is it planned to have a special function that basically says: "make dir foo and anything below (except nested subvols) a subvol named foo, immediately and atomically"? And similar vice-versa... a special function that says: "make subvol foo and anything below (except nested subvols) a dir of the parent subvol named foo, immediately and atomically"? Could be handy for real world administration, especially when one want's to avoid downtimes. btw: Few days ago, either Hugo or your thought that mv'ing a subvol would change it's UUID, but my try (which was with coreutils 8.3 -> no reflinked mv) seemed to show it wouldn't but there was no further reply then... so am I right that the UUID wouldn't change? > The same idea applies here.=C2=A0=C2=A0Once you start reaching into neste= d > subvols=20 > to get the deeper nested subvols you're trying to mount, it's too > much=20 > and you're just begging to get it wrong under the extreme pressures > of a=20 > disaster recovery. Well apparently you oversaw the extremely simple and reliable solution: leaving a tiny little note on your desk saying something like: "dear boss, things are screwed up, I'm on vacation now..." ;-) Thanks, Chris. --=-878GXYsMU839CRJLEMRp Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCCEZIw ggW/MIIDp6ADAgECAgMCOakwDQYJKoZIhvcNAQENBQAwVDEUMBIGA1UEChMLQ0FjZXJ0IEluYy4x HjAcBgNVBAsTFWh0dHA6Ly93d3cuQ0FjZXJ0Lm9yZzEcMBoGA1UEAxMTQ0FjZXJ0IENsYXNzIDMg Um9vdDAeFw0xNDA2MTIxNjM2MThaFw0xNjA2MTExNjM2MThaMHwxITAfBgNVBAMTGENocmlzdG9w aCBBbnRvbiBNaXR0ZXJlcjEkMCIGCSqGSIb3DQEJARYVY2FsZXN0eW9Ac2NpZW50aWEubmV0MTEw LwYJKoZIhvcNAQkBFiJtYWlsQGNocmlzdG9waC5hbnRvbi5taXR0ZXJlci5uYW1lMIIBIjANBgkq hkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4phP/j9vT9dZT+k3ffHxvRWMOuzBnu5O3Fl4y2+WL7pL 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