Re: [Buildroot] lvm2 seems to require systemd

[Andreas Ziegler <br015@umbiko.net>]

Hi Frank,

On 2024-07-21 09:54, Frank Wunderlich wrote:
> regards Frank
> 
> 
>> Gesendet: Sonntag, 21. Juli 2024 um 11:17 Uhr
>> Von: "Andreas Ziegler" <br015@umbiko.net>
>> An: frank-w@public-files.de
>> Cc: "buildroot" <buildroot@buildroot.org>
>> Betreff: Re: lvm2 seems to require systemd
>> 
>> Hi Frank,
>> 
>> On 2024-07-20 14:34, Frank Wunderlich wrote:
>> > Hi,
>> >
>> > i try to build a buildroot (2024.05) initrd with lvm2 support
>> >
>> > so basicly added these options:
>> >
>> > #to select BR2_PACKAGE_HAS_UDEV
>> > BR2_PACKAGE_EUDEV=y
>> > BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
>> > BR2_PACKAGE_LIBBLOCKDEV=y
>> > BR2_PACKAGE_LVM2=y
>> >
>> > build is fine, but i see this while bootup:
>> >
>> > [    3.665010] udevd[1520]: failed to execute '/usr/bin/systemd-run'
>> > '/usr/bin/systemd-run --no-block --property DefaultDependencies=
>> > no --unit lvm-activate-vg-nvme /usr/sbin/lvm vgchange -aay
>> > --autoactivation event vg-nvme': No such file or directory
>> > done
>> 
>> lvm2 installs a bunch of udev rules; one of them relies on systemd-run
>> to execute a command in the background:
>> 
>> # pvscan will check if this device completes a VG,
>> # i.e. all PVs in the VG are now present with the
>> # arrival of this PV.  If so, it prints to stdout:
>> # LVM_VG_NAME_COMPLETE='foo'
>> #
>> # When the VG is complete it can be activated, so
>> # vgchange -aay <vgname> is run.  It is run via
>> # systemd since it can take longer to run than
>> # udev wants to block when processing rules.
>> # (if there are hundreds of LVs to activate,
>> # the vgchange can take many seconds.)
>> 
>> ...
>> 
>> IMPORT{program}="/usr/sbin/lvm pvscan --cache --listvg --checkcomplete
>> --vgonline --autoactivation event --udevoutput --journal=output
>> $env{DEVNAME}"
>> ENV{LVM_VG_NAME_COMPLETE}=="?*", RUN+="/usr/bin/systemd-run --no-block
>> --property DefaultDependencies=no --unit
>> lvm-activate-$env{LVM_VG_NAME_COMPLETE} /usr/sbin/lvm vgchange -aay
>> --autoactivation event $env{LVM_VG_NAME_COMPLETE}"
>> GOTO="lvm_end"
>> 
>> > i see the physical volume, but logical volumes are disabled
>> >
>> > # pvscan
>> >   PV /dev/nvme0n1p5   VG vg-nvme   lvm2 [<1.79 TiB / <1.78 TiB free]
>> >   Total: 1 [<1.79 TiB] / in use: 1 [<1.79 TiB] / in no VG: 0 [0   ]
>> > # vgscan
>> >   Found volume group "vg-nvme" using metadata type lvm2
>> > # lvscan
>> >   inactive          '/dev/vg-nvme/var' [10.00 GiB] inherit
>> >
>> > and so i cannot mount the logical volume
>> >
>> > # mount /dev/vg-nvme/var /mnt
>> > [  281.006375] /dev/vg-nvme/var: Can't lookup blockdev
>> > [  281.011279] /dev/vg-nvme/var: Can't lookup blockdev
>> > [  281.016202] /dev/vg-nvme/var: Can't lookup blockdev
>> > [  281.021080] /dev/vg-nvme/var: Can't lookup blockdev
>> > mount: mounting /dev/vg-nvme/var on /mnt failed: No such file or
>> > directory
>> >
>> > any ideas?
>> 
>> I would try to run vgchange manually to see if the setup works at all,
>> then create a /usr/bin/systemd-run script that is able to execute
>> commands in the background. Something like this (untested):
> 
> i was able to manually initialize the lvm value after adding the 
> systemd without init (running the command without prefix 
> "systemd-run")...
> 
> basicly with this command:
> 
> /usr/sbin/lvm vgchange -aay --autoactivation event vg-nvme
> 
> with init i had compile issues missing libmount, see my followup post
> 
> now i have to remove systems from my initrd somehow to do further 
> testing with only the eudev. any idea doing this without making all 
> clear (or is this dropped when recreating the cpio file)?

Without running make clean, unwanted files need to be removed manually. 
Buildroot creates per-package logs .files-list, 
.files-list-{host,images,staging}, which contain the names of files 
copied to the respective destination. Remove at least those from 
.files-list to revert to a system without the package; preferrably also 
those from .files-list-staging.

Kind regards,
Andreas

> 
>>    #!/bin/sh
>>    prg=$1
>>    shift
>>    (
>>      $prg $@ < /dev/zero > /tmp/error.log 2>&1
>>    )&
> 
>> Kind regards,
>> Andreas
>> 
>> > regards Frank
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