lvm2: systemd fixes and update #88565

ajs124 · 2020-05-22T01:36:52Z

Motivation for this change

We're deploying lvmthin and they recommend running dmeventd, and while there is an option on the lvm2 package, it sort of didn't work.

The update is in there, because our current version is from October of 2018.

Things done

This probably needs a changelog entry and some documentation updates, because:

it's probably worth noting that we support lvm2 services now. You can run dmeventd simply by setting systemd.packages = with pkgs; [ lvm2 ]; and systemd.sockets."dm-event".wantedBy = [ "sockets.target" ];. And mabye you also need a lvm.conf. (And also lvm2.override { enable_dmeventd = true; }).
blk_availability_systemd_red_hat.service and lvm2_activation_generator_systemd_red_hat are currently manually installed with these names. Using the upstream install they're simply called blk-availability.service and lvm2-activation-generator.

I haven't looked through the commit history that much, but I'm wondering why dmeventd is optional in the first place. Is the difference in closure size really that big?

There's also at least two other lvm daemons (lvmetad and lvmpoold), which we're not shipping right now.

Point 1. above might also warrant the introduction of a small module to configure dmeventd and the other daemons, if anyone is interested in those.

- use installTargets again ("install", and "install_systemd_{generators,units,configuration}" when udev is not null) - The call to the blkid binary in lvm2's 13-dm-disk.rules file disappeared (so we don't need to patch in blkid anymore). lvm seems to rely on udev's internal blkid functionality. - Call /run/current-system/systemd/bin/udevadm instead of ${systemd}/bin/udevadm in the lvm activation generator. This is not necessary to break the dependency cycle (as we don't use that file when building without udev), but a good idea anyways - We want to trigger the udevadm of the current system, not the one that lvm was built with.

Otherwise, we end up in a dependency cycle: systemd -> cryptsetup -> lvm -> fetchgit -> git -> openssh -> libfido2 -> hidapi -> libusb -> udev=systemd

7c6f434c · 2020-05-23T02:29:14Z

I would guess that nobody wanted to check if dmeventd is fully ignorable if enabled (although the man page seems to suggest so). The dependency set does not seem to differ, so I guess making it on by default should be safe. Same with the other daemons, hopefully.

As for modules — well, I guess this is a necessary step to eventually having a NixOS test for all that…

No idea whether addition of more things should be mentioned in release notes (but I am not a user of stable), renaming installed files probably is a good thing to mention. (I wonder if it breaks some rev-deps…)

ajs124 · 2020-05-23T15:27:25Z

I looked a bit more into this. Turns out lvmetad isn't part of lvm2 anymore. lvmpolld still exists, though.

For turning them off there is global/use_lvmpolld and activation/monitoring.

The other daemons include some python d-bus stuff and cluster stuff (lvmlockd, cmirrord), but I'd not add them right now, as we don't use them and I don't really know how to test them.

As for tests, there is nixos.tests.installer.lvm, but it's pretty basic.

The main hold-up for extending nixos/modules/tasks/lvm.nix with thin support is that #46541 never got merged, for valid reasons, but with #72401 still in progress, not much has changed on that front.

There's a circular dependency to systemd via cryptsetup and lvm2 (systemd -> cryptsetup -> lvm2 -> udev=systemd). However, cryptsetup only really needs the devmapper component shipped with lvm2. So build `pkgs.cryptsetup` with a lvm2 that doesn't come with udev.

…yptsetup-generator.c)

This package previously did override the systemd package, and instructed ninja, systemd's previous build system, to only build the cryptsetup-specific systemd generators (plus some rpath massaging, as we didn't use ninja install). Afterwards, users were expected to add this package to their `systemd.generator-packages` (or since https://github.com/NixOS/nixpkgs/pull/65376/files `systemd.packages`) NixOS module options, so systemd will use these generators. As the previous commit added cryptsetup support directly to the systemd package (and pkgs.systemd now already ships the cryptsetup generators), we don't need another package shipping the same generators.

Instead, prompt user to add lvm to systemd.packages, which is a cleaner way, and we don't need to rebuild the world by changing systemd globally. Initially introduced in c0fd887.

We might want to do this conditionally on whether lvm is enabled (or add the lvm system-generators unconditionally, too)

This seems to be mostly used to simplify LV management tasks from a web interface (https://www.redhat.com/archives/linux-lvm/2008-September/msg00029.html), and is as fat as the `lvm` binary itself

7c6f434c · 2020-05-25T00:30:18Z

Well, maybe it is enough for the first step just not to break the basic operation…

So, for this PR what is needed is a release note entry that we rename installed files back to upstream names?

ajs124 · 2020-05-31T21:41:20Z

Enabling dmeventd doesn't actually work right now, because of

cycle detected in the references of '/nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib' from '/nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin'

Not sure how to fix that while keeping the split outputs.

flokli · 2020-06-01T21:53:31Z

@ajs124 I propose checking the outputs, and /why/ there are these circular references.

ajs124 · 2020-06-01T23:17:30Z

It's not that much of a "why", but:

find /nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib -type f -exec strings -f {} + | grep /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin

/nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib/libdevmapper-event.so.1.02: /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin
/nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib/liblvm2cmd.so.2.03: /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/fsadm
/nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib/liblvm2cmd.so.2.03: /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/dmeventd
/nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib/liblvm2cmd.so.2.03: /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/lvm

find /nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin -type f -exec strings -f {} + | grep /nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib
/nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/dmeventd: /nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib:/nix/store/xrxbwxsvdsj07cgfpxmxk2qzvwmrnv3j-systemd-245.5-lib/lib:/nix/store/9s2w6ahf8zxdip7nhybs8gkzfbln6cxv-util-linux-2.35.1/lib:/nix/store/bwzra330vib0ik4d3l8rq6gp6y2ah1fr-glibc-2.30/lib
/nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/dmsetup: /nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib:/nix/store/bwzra330vib0ik4d3l8rq6gp6y2ah1fr-glibc-2.30/lib
/nix/store/nhrji14hh4nq3grg1jzgkrzbp04qymg1-lvm2-2.03.09-bin/bin/lvm: /nix/store/9x3ny30dvb8i2lrc5pybgjvrjci4hb3x-lvm2-2.03.09-lib/lib:/nix/store/xrxbwxsvdsj07cgfpxmxk2qzvwmrnv3j-systemd-245.5-lib/lib:/nix/store/9s2w6ahf8zxdip7nhybs8gkzfbln6cxv-util-linux-2.35.1/lib:/nix/store/bh2lqv8646c12hfrb4ympygv7qz9x2ck-libaio-0.3.110/lib:/nix/store/bwzra330vib0ik4d3l8rq6gp6y2ah1fr-glibc-2.30/lib

flokli · 2020-06-02T09:29:30Z

Yeah, I dropped liblvm2cmdfrom the expresssion - it's "a library aiming to simplify typical LV management tasks from a web interface" - see 3b7d76b.

If dmeventd now depends on it as well, that'll make things more complicated. How do other distros handle this? It seems it's not installed in Gentoo as well.

ajs124 · 2020-06-02T16:14:22Z

The problem isn't only liblvm2cmd though. The problem is also that libdevmapper-event.so depends on bin when dmeventd is enabled and dmeventd, lvm and dmsetup depend on libdevmapper-event.so.

flokli · 2020-06-14T10:33:00Z

I'm not entirely sure which of the components are needed for lvm operation these days - I mostly introduced the multiple outputs to get the closure size down, as systemd only uses the devmapper components shipped inside lvm.

ajs124 · 2020-06-15T15:17:25Z

I'm not entirely sure which of the components are needed for lvm operation these days

I'm not sure what either, to be honest.

I mostly introduced the multiple outputs to get the closure size down, as systemd only uses the devmapper components shipped inside lvm.

That's what I assumed. Reducing closure size for something like systemd is always a good idea.

The question is where we go from here. I can spend some time to figure out which parts of LVM are relevant for what, which is probably relevant to us in any case.
However, that might lead to the conclusion that features like dmeventd or lockd are incompatible with multiple outputs. It's probably technically possible to disable the multiple outputs in case such a feature is activated, but that's sounds ugly.

flokli · 2020-06-15T17:50:19Z

I'm all fine with reducing some of the multiple-output stuff, if it's necessary to get LVM to work - if closure sizes are a problem, we can still re-evaluate.

Does your PR currently build, and does the new test succeed?

In that case, I could cherry-pick this into #66856, possibly squashing some of the changes for readability.

Did you check the closure size of the minimal iso before and after this change?

ajs124 · 2020-06-18T00:58:31Z

It doesn't build as is, but probably builds and runs fine without multiple outputs.

I haven't checked the closure size yet. Not sure when I'll get around to put some time into this, might not happen before next week, sorry.

flokli · 2020-07-12T11:34:07Z

@7c6f434c I incorporated this back into #66856 (comment), feel free to take a look :-)

flokli added 3 commits May 5, 2020 21:41

lvm2: remove unused default.upstream file

c7fb00e

lvm2: fetch sources from http instead of git

f19b938

Otherwise, we end up in a dependency cycle: systemd -> cryptsetup -> lvm -> fetchgit -> git -> openssh -> libfido2 -> hidapi -> libusb -> udev=systemd

ofborg bot requested a review from 7c6f434c May 22, 2020 01:45

ofborg bot added 11.by: package-maintainer 10.rebuild-darwin: 11-100 10.rebuild-linux: 101-500 labels May 22, 2020

flokli and others added 8 commits May 24, 2020 02:36

systemd: substituteInPlace paths to mkswap and mke2fs (used in new cr…

afc6137

…yptsetup-generator.c)

systemd_with_lvm2: remove

b322f24

Instead, prompt user to add lvm to systemd.packages, which is a cleaner way, and we don't need to rebuild the world by changing systemd globally. Initially introduced in c0fd887.

nixos/systemd: add tmpfiles from lvm2

eb03c0a

We might want to do this conditionally on whether lvm is enabled (or add the lvm system-generators unconditionally, too)

lvm2: make --enable-cmdlib optional

3b7d76b

This seems to be mostly used to simplify LV management tasks from a web interface (https://www.redhat.com/archives/linux-lvm/2008-September/msg00029.html), and is as fat as the `lvm` binary itself

lvm2: don't embed ./configure line in lvm2 binary

00a1e53

lvm2: add multiple output support

88bc0a1

ajs124 mentioned this pull request May 24, 2020

systemd: build with cryptsetup support, add cryptsetup generators #66856

Merged

10 tasks

ajs124 added 7 commits May 25, 2020 03:33

lvm2: fix dmeventd paths

9093ddf

lvm2: 2.03.01 -> 2.03.09

50c4801

lvm2: add myself as maintainer

5f91ab1

nixos/tasks/lvm: add dmeventd and lvmthin support

a06b286

nixos/test/installer: add postBootCommands

cb35d3a

lvm2: dmeventd depends on cmdlib

44c2cdf

nixos/tests/installer: add lvmSystemdGenerator test

80501a1

ajs124 marked this pull request as draft May 31, 2020 21:38

ajs124 force-pushed the lvm2 branch from 5bf657f to 80501a1 Compare May 31, 2020 21:38

ofborg bot added the 6.topic: nixos label May 31, 2020

ofborg bot added 8.has: module (update) 8.has: clean-up labels May 31, 2020

ofborg bot requested review from edolstra, lovek323, flokli and andir May 31, 2020 21:46

ofborg bot added 10.rebuild-darwin: 101-500 10.rebuild-linux: 501+ 10.rebuild-linux: 5001+ and removed 10.rebuild-darwin: 11-100 10.rebuild-linux: 101-500 labels May 31, 2020

ajs124 closed this Jul 12, 2020

ajs124 deleted the lvm2 branch March 11, 2021 16:21

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

lvm2: systemd fixes and update #88565

lvm2: systemd fixes and update #88565

ajs124 commented May 22, 2020

7c6f434c commented May 23, 2020

ajs124 commented May 23, 2020

7c6f434c commented May 25, 2020

ajs124 commented May 31, 2020

flokli commented Jun 1, 2020

ajs124 commented Jun 1, 2020 •

edited

flokli commented Jun 2, 2020

ajs124 commented Jun 2, 2020

flokli commented Jun 14, 2020

ajs124 commented Jun 15, 2020

flokli commented Jun 15, 2020 •

edited

ajs124 commented Jun 18, 2020

flokli commented Jul 12, 2020 •

edited

lvm2: systemd fixes and update #88565

lvm2: systemd fixes and update #88565

Conversation

ajs124 commented May 22, 2020

Motivation for this change

Things done

7c6f434c commented May 23, 2020

ajs124 commented May 23, 2020

7c6f434c commented May 25, 2020

ajs124 commented May 31, 2020

flokli commented Jun 1, 2020

ajs124 commented Jun 1, 2020 • edited

flokli commented Jun 2, 2020

ajs124 commented Jun 2, 2020

flokli commented Jun 14, 2020

ajs124 commented Jun 15, 2020

flokli commented Jun 15, 2020 • edited

ajs124 commented Jun 18, 2020

flokli commented Jul 12, 2020 • edited

ajs124 commented Jun 1, 2020 •

edited

flokli commented Jun 15, 2020 •

edited

flokli commented Jul 12, 2020 •

edited