This is another objective that is not very useful by itself, after all once you create a logical volume, you still have to create a file system and mount it, anyway, let's get cracking.
Assuming you have an empty disk you can simply do the following to create a physical volume:
pvcreate /dev/sdc - this assumes that you have a a device called /dev/sdc
This is not very useful, namely to have a single physical volume, the only thing you have done is given yourself the oportunity to add more storage later, which is not actually a great thing, but for this objective you are better off with at least two disks.
Before we move any further, let's cover the remove physical volumes objective:
pvremove /dev/sdc
There are limitations to what the command can do, e.g. don't expect it to remove a physical volume that has a volume group.
Note that the -ff option will remove it almost no matter what, use at your own risk.
You can list the physical volumes with the following commands:
pvs
pvdisplay
Assuming that you have created two physical volumes, /dev/sdc & /dev/sdd, we can create a volume group like this
vgcreate volname /dev/sdc /dev/sdd
Alternatively, you could this to mimic a real life situation where you create a logical volume, run out of space and need to extend, in which case you add a new physical volume to the volume group:
vgcreate volname /dev/sdc - this creates the volume group volname
vgextend volname /dev/sdd - this adds the /dev/sdd phyical volume to the volname volume group
Say you made a mistake and you actually wanted to add /dev/sde rather than /dev/sdd to volname, just run the following
vgreduce volname /dev/sdd - needless to say that there will be limitations to this command as well
You can list the volume groups with the following commands:
vgs
vgdisplay
And finally we come to the useful part, the logical volumes, by now, you probably have sussed out what the commands are going to be: lvcreate, lvremove, lvs, lvdisplay, 100% right.
lvcreate -l 10%VG volname -n lvol1 - This will create a logical volume called lvol1 that is 10% the size of the volumegroup volname.
lvcreate -L 500M volname -n lvol2 - This will create a logical volume called lvol2 that is 500M, this will only work if there is enough free space in volname.
lvcreate -i 2 -l 10%FREE volname -n lvol3 - This will create a logical volume called lvol3 that is 10% of the size of the space left in volname. The -i 2 switch will ensure that volume group spans two physical volumes, again this will only work if there are two or more physical volumes.
You've just realized that you wanted a bigger lvol3, no problem, just extend it with:
lvextend -l 20%FREE /dev/volname/lvol3
The lvreduce command behaves in a similar manner
In order to delete the lvol3 you would type:
lvremove /dev/volname/lvol3
or
lvremove /dev/mapper/volname-lvol3
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