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