[linux-lvm] boot volume in activated containing PV does not activate

Linda A. Walsh lvm at tlinx.org
Mon Nov 7 16:58:08 UTC 2016

Xen wrote:
> Now at boot (prior to running of systemd) I activate both 
> coll/msata-lv and msata/root.
    Systemd requires that it be PID 1 (the first process to run
on your system).  I'm told that it won't run unless that is true.  So
how can you do anything before systemd has been run?
> This works fine when both mirrors are present.
> As a test I removed the primary (SSD) mirror of the root volume (and 
> the boot volume). Now the system still boots (off of another disk 
> which has grub on it, but only the grub core and boot image, nothing 
> else, so it still references my VG) and the root volume still gets 
> activated but the boot volume doesn't get activated anymore.
> What can cause this? It ought to get activated by udev rules.
> You remember I patched the udev file to ensure a PV directly on disk 
> always gets activated but this is not that disk.
> Could it be that the msata/boot volume doesn't get activated because 
> the PV had already been activated in the initrd but only as an LV and 
> not its volumes?
    Sounds very similar to opensuse's requirement that /usr be on
the same partition as root -- if not, then you have to boot using
a ramdisk, which mounts /usr, and then does the real system boot, so
of course, booting directly from disk (which is what my machine does)
is not supported.  I also mount "/usr" as a first step in my boot
process, but that disallows a systemd boot, which some define as
systemd being pid 1.

    I'm told systemd has changed the meaning of 'fstab' to not
be a table of disks to mount, but to be a table of disks to keep mounted
(even if umount'd by an administrator).  Since udev's functionality was
incorporated into systemd, might it not be doing something similar --
trying to maintain the boot-state in effect before you added the mirror?

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