Configuring the 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 (usually the most important one) was short on
space, while some other partition was grossly underused and you had to
manage this situation by 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 disk (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 disks.
Now when you realize you need more space for your old 160GB
/home partition, you can simply add a new 300GB
disk 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 and completely supported inside
partman. First, you have to mark the partition(s)
to be used as physical volumes for LVM. This is done in the
Partition settings menu where you should select
Use as: physical volume
for LVM .
When you return to the main partman screen, you will see
a new option Configure the Logical Volume Manager.
When you select that, you will first be asked to confirm pending changes to
the partition table (if any) and after that the LVM configuration menu will
be shown. Above the menu a summary of the LVM configuration is shown. The
menu itself is context sensitive and only shows valid actions. The possible
actions are:
Display configuration details:
shows LVM device structure, names and sizes of logical volumes and more
Create volume group
Create logical volume
Delete volume group
Delete logical volume
Extend volume group
Reduce volume group
Finish:
return to the main partman screen
Use the options in that menu to first create a volume group and then create
your logical volumes inside it.
After you return to the main partman screen, any created
logical volumes will be displayed in the same way as ordinary partitions
(and you should treat them as such).