Re: Converting from EVMS on Debian

Hello Ross, hello group,

thanks a lot for sharing your experiences, they helped me a lot in 
migrating back to plain mdadm+lvm2. One of the main purposes I am 
running a LVM is to be able to do snapshotting for backups. 
This feature is regrettably not usable any more with latest evms 
on debian etch, so I had to leave beloved evms...

I have to agree, that the whole procedure was not really easy to do 
and not just a matter of converting to compatibility volumes. 
Therefore just a few comments.

1) My system was Debian etch (stable). 
- According to the already described procedure I changed evms volumes to
compatibility volumes (easy within a debug shell of the initrd or with
evmsdebug)
- Removed evms package via aptitude (mdadm and lvm2 were installed beforehand)
- mount /dev/real_root /target
- mount -o bind /sys /target/sys
- mount -o bind /proc /target/proc
- mount -o bind /dev /target/dev
- chroot /target
- update-initramfs -u
- umounting

now, really thank you, Ross, I would never have imagined syntax of kernel
parameter:
- rebooting with new initrd and 
   kernel parameter root=/dev/mapper/volgr-volname

after some trials got behind "waiting for root device...", but 
nevertheless md0 wasn't activated (raid0 with 2 scsi disks for 
home and var) neither other volume groups on living on hdc.
- repeated chroot to real_root and I *believe*, that either 
  just starting mdadm or doing mkraid /dev/md0 activated md0
- repeated update-initramfs -u
- after reboot md0 activated, but no volume groups

once again procedure 
- chroot to real_root
- vgchange -ay
  no volume groups detected, use vgscan
- vgscan
  output: vgscan -- LVM driver/module not loaded?

since the machine was/is my server, no connection to net. I *thought* 
to have all information ready on my desktop before disconnecting from net.

- since vgchange etc. are links to lvm, I tried direct call to lvm and VOILA:
- in the prompt of lvm I could succesfully do vgchange -ay
- mounting /home and /var manually
- happily booting first time in normal system (now fully lvm2 based)
- rebuilt initrd once again

nevertheless, after rebooting still no activation of vol groups. Looking at
scripts at /usr/share/initramfs-tools revealed, that vgchange was 
executed via link and probably activation failed due to this mode of call.

Before changing initrd scripts I tried with newest versions from testing.
Backported 
    * libdevmapper1.02
    (libdevmapper-dev (needed for lvm2))
    * lvm2
from testing.

- installed backports
- rebuilt initrd
- rebooted
- joy!

Conclusion:
If you try to convert from evms to lvm2 on Debian stable, get some backports 
for libdevmapper and lvm2 first.

Now looking ahead to create the first snapshots on the system.

Mathias



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