Convert ext4 lvm to normal ext4 partition
Patrick O'Callaghan
pocallaghan at gmail.com
Fri Nov 12 18:29:52 UTC 2010
On 12/11/10 1:13 PM, Michael Miles wrote:
> Considering that the LVM is a ext4 Virtual partition it seems to me
> that it would be easy to convert but there is no such beast out there
> Lots of stuff for converting ext3 to ext4 but nothing for what I need.
This is pure speculation on my part, but I'm guessing one reason it's
hard is that the LVM layer knows nothing about the ext4 layer. The ext4
layer contains lots of metadata (inodes, freelists, etc.) which includes
pointers to disk sectors or extents. In a physical partition these point
to real disk addresses but in an LVM partition they are virtual (compare
real with virtual memory for an analogy). From LVM's viewpoint the
entire ext4 fs is just disk sectors with random binary data. The fact
that some of this stuff is fs metadata and some isn't means that a
conversion tool would need to understand the ext4 metadata to convert
it. Of course if it's ext3 or xfs or btrfs etc. then the same applies,
with different rules for each one.
Worse still, if you want a in-place conversion you have to be able to do
this in such a way that it's recoverable even after a hard system crash
in the middle of the conversion. And if you don't need it in-place, you
already have the solution as said before.
Just my 2 cents.
poc
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