Opened 5 years ago

Last modified 5 years ago

#755 new enhancement

Limit LVM scope

Reported by: jonathan.senning@… Owned by:
Priority: minor Milestone:
Component: Both Version:
Keywords: Cc:
Blocked By: Blocking:
Estimated Hours: 8 Total Hours: 0

Description

On 12/05/2012 10:58 AM, Mohammad Mobeen Ludin wrote:

I was about to post the following note to the BCCD developers list but thought I'd send it to you first. I'm happy to post it, but I don't feel like I really understand the list etiquette yet. In particular, is it just for the developers to communicate with each other or is it a place where uses like me can ask questions of the developers?

Please let me know if I should post this or perhaps send it to someone (you? Skylar? Aaron?) directly.

Its always best to send an email to bccd-developers when you have questions related to BCCD for many reasons. different people are working on different task so that way the appropriate person could answer your question without leading you to some mysteries, you will get a quick response (eg. if i am busy someone else will reply), we can keep track of issues people are having so we can discus them in our meetings and try to resolve, etc. (someone else could jumpin here and add couple more)

During the liberate process it appears that all LVM data may be removed from all attached drives.

In my case I had the following configuration: /dev/sda -- the LittleFe? hard drive with OS already installed /dev/sdb -- USB boot drive with BCCD 3.2.0 boot image on it (created with unet bootin) /dev/sdc -- 4GB USB flash drive I was trying to liberate BCCD to After booting off /dev/sdb and modifying /root/liberate.pl so the amount of swap space created would be 0.5*ramsize rather than 2*ramsize I ran perl ./liberate.pl --libdev /dev/sdc This ran as expected but I noticed that one of the first tests done indicated that LVM information was cleared from all drives. Sure enough, I was unable to boot off the hard drive /dev/sda again until repairing the LVM data as described in the first half of http://microdevsys.com/wp/linux-lvm-recovering-a-lost-volume/

Is it necessary for all LVM data to be cleared from all attached drives? Could the liberate script only modify the data on the destination drive? (I don't know a whole lot about how LVM works). In any event, a warning that all attached drives are about to be modified and giving the user a chance to abort would be helpful.

Thats a good question. To be honest I am not very clear/helpful answer for it. I looked into the script and and its meant to clear all LVM data, but not sure exactly why. The only reason I could think of it maybe disk/usb partitions and to avoid having conflicting LVM data on different partitions. (I could be very wrong here: not very familiar with LVM either.)

any actually useful thoughts Charlie + Skylar or etc on this ????

We can make a best effort to ensure that LVM only affect the physical device provided by --libdev, although the nature of LVM is that the logical volumes (what the filesystem sees) are abstracted away from the physical devices. This means that a logical volume could span multiple physical devices, so removing a physical volume could impact logical volumes that have extents elsewhere.

If it's useful, I could try to make liberation a bit more intelligent and try not to zorch more than is needed.

Skylar

Change History (1)

comment:1 Changed 5 years ago by skylar

  • Reporter changed from skylar to jonathan.senning@…
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