Configuring Logical Volume Manager (LVM)
If you are working with computers at the level of system administrator
or advanced
user, you have surely seen the situation
where some disk partition (usualy the most important one) was short on
space, while some other partition was grossly underused and you had to
manage this situation with moving stuff around, symlinking, etc.
To avoid the described situation you can use Logical Volume Manager
(LVM). Simply said, with LVM you can combine your partitions
(physical volumes in LVM lingo) to form
a virtual disc (so called volume group), which
can then be divided into virtual partitions (logical
volumes). The point is that logical volumes (and of course
underlying volume groups) can span across several physical discs.
Now when you realize you need more space for your old 160GB
/home partition, you can simply add a new 300GB
disc to the computer, join it with your existing volume group and then
resize the logical volume which holds your /home
filesystem and voila - your users have some room again on their
renewed 460GB partition. This example is of course a bit
oversimplified. If you haven't read it yet, you should consult the
LVM HOWTO.
LVM setup in &d-i; is quite simple. At first, you have to mark your
partitions to be used as physical volumes for LVM. (This is done in
partman in the Partition
settings menu where you should select
Use as: physical volume for
LVM .) Then start the
lvmcfg module (either directly from
partman or from the &d-i;'s main menu) and combine
physical volumes to volume group(s) under the Modify
volume groups (VG) menu. After that, you should create
logical volumes on the top of volume groups from the menu
Modify logical volumes (LV).
After returning from lvmcfg back to
partman, you will see any created logical volumes
in the same way as ordinary partitions (and you should treat them like
that).