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I have 2 harddrives in my system, managed by LVM

vg1 (on /dev/sda2)
lv_root
lv_swap


vg2 (on /dev/sdb2)
lv_root
lv_swap

I removed the sdb HDD and when booting it has gotton slower and drops into debug mode and dmesg shows me:

dracut: Scanning sda2 for LVM logical volumes vg1/lv_root vg1/lv_swap vg2/lv_root vg2/lv_swap
dracut: inactive /dev/vg1/lv_swap inherit
dracut: inactive /dev/vg1/lv_root inherit
Volume group vg2 not found
Skipping volume group vg2
dracut: Warning: No root device "block:/dev/mapper/vg_myname-lv_root" found
dracut: /dev/mapper/vgmyname-lv-swap" not found.

It's the same issue as here: http://forums.fedoraforum.org/showthread.php?t=265470

Answer:

The problem was that the bootloader looked for the removed swap logical volume. All I had to do was to edit grub.confand reboot.

Just to be sure I also deactivated the drive in KDE's 'Disk Utility'.

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2 Answers

Before you can remove the disk, you need to migrate the data to another disk.

If I'm interpreting your question right, you appear to have different Volume Groups on different disks. In that case, your simplest solution would be just to make a new VG on a new disk, make a new lv on that vg, and copy the disk however you like.

If you want to get complicated, you can add the new disk (pv) to VG2 using vgextend vg2 /dev/sdc1. Then you migrate all the data off of the old disk onto the new one using pvmove /dev/sdb1 /dev/sdc1, then remove it from the vg using vgreduce vg2 /dev/sdb1

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Hi - yes I have different Volume Groups on different Disks. One disk is from Computer A and one is from Computer B. Unfortunately both disks were plugged in during OS installation, but I made sure that the OS is getting installed ONLY on the Computer A disk. Now i want to remove Computer B disk without loosing data or having to copy it? When I pull the cable from Computer B disk, the data remains on the disk, so everything is fine. But I get error messages that say dev/mapper cldnt find lv_root and lv_swap on Computer A disk (plugged in). HTH –  Achmed Durangi Jun 19 '11 at 18:16
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A likely cause is that you have filesystems on the volume group(s) that the drive provides physical volume(s) for, and the error is the OS trying to mount these on boot. Check your /etc/fstab/ for this issue.

It would be helpful to include the text of the relevant part of the boot sequence. "some device mapper error messages" isn't all that helpful from a remote diagnostics point-of-view.

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You are right. The error message was from "dracut" on FC15 saying: "dracut: Warning: No root device "block:/dev/mapper/vg_myname-lv_root" found" –  Achmed Durangi Jun 19 '11 at 18:09
    
I saw now in my LVM GUI that both swap LVs are unmounted. –  Achmed Durangi Jun 19 '11 at 18:12
    
Maybe I could write in the fstab "/dev/vg_myname-lvroot" instead of "/dev/mapper/vg_myname-lv-root /" ? –  Achmed Durangi Jun 19 '11 at 18:15
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