[Mageia-dev] System doen't boot with LVM

Mon Feb 18 16:15:56 CET 2013

'Twas brillig, and Olivier Thauvin at 18/02/13 14:55 did gyre and gimble:
+> * Colin Guthrie (mageia at colin.guthr.ie) wrote:
+>> 'Twas brillig, and Olivier Thauvin at 18/02/13 12:48 did gyre and gimble:
+>>> So ok, I just update my freshly installed mga2 to cauldron using network
+>>> install (live upgrade don't work, it seems urpmi fail to find a way to
+>>> update the system w/o filesystem).
+>>>
+>>> I have the exact same result: it don't boot.
+>>
+>> Hmm, re: live upgrade are you meaning just a urpmi based upgrade? If so,
+>> I've done a few similar updates in the last week or so in VMs and it's
+>> always been OK. I presume you installed the mageia-prepare-upgrade
+>> package from mga2/core/updates_testing, rebooted to the boot menu entry
+>> created by that package before upgrading?
+> 
+> Ha, no, I followed the howto on the wiki:
+> https://wiki.mageia.org/en/Feature:UsrMove
+> 
+> and there is no reference to this package on the page :\
+
+Yeah, I noticed that too this morning :s I'll update it (I could have
+sworn I had already, but.... I guess not - it was posted about quite a
+lot on the list but that's fairly transient and no excuse for my general
+failure to update the wiki!).
+
+The mageia-prepare-upgrade package is just a nice wrapper around those
+commands anyway, so you should be 99% OK with those commands all the
+same (although they certainly are more complicated than they now need to
+be - they were originally written for cauldron users during the
+transition process rather than a clean mga2->mga3, so this explains
+where there are urpmi commands with skip etc. in them. I think the time
+is such that I can remove some of that detail from the page - the number
+of cauldron users running pre-usrmove must be ~= 0 by now :)
+
+>> Regarding the network install based upgrade there may be issues relating
+>> to bootloader config tools (in drakx) that related the use of the blkid
+>> cache which might make it miss the whole LVM volume (I've seen it
+>> manifest itself as putting "root=/dev/" into grubs menu.lst rather than
+>> "root=/dev/mapper/foo").
+> 
+> The entry in grub is fine (just checked it).
+
+Good :)
+
+>>>> In the dracut shell, what does /etc/cmdline.d/lvm.conf say? It should
+>>>> contain enough info to brink up both the root and the swap lvm.
+>>>
+>>> rd.lvm.lv=sagittarius/swap
+>>
+> 
+>> The problem is that dracut itself is not detecting that the LV needs
+>> activating when it runs.
+>>
+>>
+>> In order to get a booting system, just pass "rd.lvm.lv=sagitarius/slash"
+>> on the command line (obviously substituting the real name of your
+>> logical volume). This should make dracut initialise the lvm automatically.
+> 
+> This method did work and I am now under linux.
+
+Yay! Lucky that the 51-mageia-resume.conf file caused the lvm module to
+be included in the first place otherwise the initrd wouldn't have the
+lvm command in it at all :D
+
+> What can I do to understand why dracut did not detect the lvm to
+> activate properly (and hopefully fix this definitivelly) ?
+
+Basically, the best bet is to run something like the following (as root):
+
+dracut -f foo.img
+mkdir foo
+cd foo
+zcat ../foo.img | cpio -id
+cat etc/cmdline.d/lvm.conf
+
+This should test whether your / lvm has been detected in addition to the
+swap one.
+
+I sort of hope that this fails, otherwise the problem will be harder to
+nail down!!
+
+If it does fail then ultimately the problem will be in:
+/usr/lib/dracut/modules.d/90lvm/module-setup.sh (or one of the utility
+functions it uses). It should use "udevadm info" to query the system
+about LVM info. You can add debug to the check_lvm function and then
+re-run dracut -f foo.img again to see where it bails out.
+
+
+If, however, it works fine on your running system then perhaps the
+problem is with the installer lacking some udev rules to properly
+capture all the needed metadata in udev database. This will require a
+bit more fiddling (i.e. running udevadm info in the installer to look at
+the properties it exports about the devices).
+
+>> You should (at least in theory) also just be able to type something like
+>> "lvm vgchange -ay" into the dracut shell, then type exit (perhaps twice)
+>> to continue the boot process.
+> 
+> This has work except I was unable to enter my passphrase to read my
+> encrypted /home.
+
+Ahh yes, the "lvm vgchange -ay" is a bit of a "enable everything"
+command (normally the initrd only initialises what it absolutely must -
+e.g. /, /usr and swap for resume= support). I guess it might mess up the
+passphrase stuff later on as a knock on effect, but really /home (and
+any passphrase needed for it) should be the domain of the booted system
+rather than the initrd (in theory!)
+
+> But it's good to know this is posible.
+
+Yeah. the lvm command is only included if dracut detects lvm as being
+needed. In your current example it was somewhat fortunate that your swap
+was on LVM and the 51-mageia-resume.conf file detailed that. This
+51-mageia-resume.conf is a bit of a hack really... I should likely find
+a nicer way to do it without hard-coded configs :)
+
+Col
+
+-- 
+
+Colin Guthrie
+colin(at)mageia.org
+http://colin.guthr.ie/
+
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+  Tribalogic Limited http://www.tribalogic.net/
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+