====== LVM ======
===== - Resize logical volume =====

  * [https://fabianlee.org/2016/07/26/ubuntu-extending-a-virtualized-disk-when-using-lvm/
  * [http://blog.shadypixel.com/how-to-shrink-an-lvm-volume-safely/
  * [http://alexeytorkhov.blogspot.de/2009/09/mounting-raw-and-qcow2-vm-disk-images.html

The steps are as follows:
  - Create new disk partition with fdisk (after extending virtual disk of the VM or physical disk of the computer). Restart.
  - Check things with pvdisplay, vgdisplay, lvdisplay
  - Create the LVM Physical Volume: pvcreate /dev/sdaX
  - Extend the LVM Volume Group: vgextend ubuntu-vg /dev/sda3
  - Extend the LVM Logical Volume, use all space and resizefs (-r): lvextend -r -l +100%FREE /dev/ubuntu-vg/ubuntu-lv
  - Validate: df -h

==== - Resize root lv ====

Resize2fs already done with -r key above. Otherwise:
    resize2fs /dev/ubuntu-vg/ubuntu-lv
    
    df -h
    lsblk
===== - Mount Resize QCOW2 =====

    modprobe nbd max_part=63
    qemu-nbd -c /dev/nbd0 Fedora-x86_64-20-20141008-sda-compute.qcow2
    mount /dev/nbd0p2 /mnt/cf
    error mounting lvm2_member
    fdisk -l 
    show nothing

<code>    
    lvmdiskscan
      /dev/fedora_dai142/lv_root   [      78.12 GiB] 
  /dev/sda1                    [     200.00 MiB] 
  /dev/nbd0p1                  [     500.00 MiB] 
  /dev/fedora_dai142/lv_swap00 [       9.77 GiB] 
  /dev/sda2                    [     500.00 MiB] 
  /dev/nbd0p2                  [       9.51 GiB] LVM physical volume
  /dev/fedora_dai142/lv_home   [     117.19 GiB] 
  /dev/sda3                    [     205.08 GiB] LVM physical volume
  /dev/sdb1                    [     300.00 GiB] 
  /dev/sdb2                    [      10.00 GiB] 
  /dev/sdb3                    [     246.12 GiB] 
  /dev/sdb4                    [     375.39 GiB] LVM physical volume
  2 disks
  7 partitions
  0 LVM physical volume whole disks
  3 LVM physical volumes
</code>
===== - Dont know how to resize =====

===== - Clean up =====
    qemu-nbd -d /dev/nbd0
    vgchange -an VolGroupName
    killall qemu-nbd

====== - Virt-resize ======
  * [http://linux.die.net/man/1/virt-resize
Basically: Copy old-image to new-image +resize
   
Create new image
    
    qemu-img create -f qcow2 newdisk.qcow2 15G

===== - Find out which sdx to expand and which logical volume =====

Mount qcow2 image with guestfish

Mount the image in read-write mode as root, as follows:

    # guestfish --rw -a Fedora-x86_64-20-20141008-sda-compute.qcow2
        
We must first use the run command at the guestfish prompt before we can do anything else. This will launch a virtual machine, which will be used to perform all of the file manipulations.

    ><fs> run
    ><fs> list-devices
    /dev/sda1
    /dev/sda2
    ><fs> list-filesystems
    /dev/fedora/root: ext4   <-- here it is
    /dev/fedora/swap: swap
    
We're done, so we can exit using the exit command:

    ><fs> exit

===== - Expand image    ===== 
    virt-resize --expand /dev/sda2 --LV-expand /dev/fedora/root \
      olddisk newdisk

<code>
virt-resize --expand /dev/sda2 --LV-expand /dev/fedora/root \
> Fedora-x86_64-20-20141008-sda-controller.qcow2 Fedora-x86_64-20-20141008-sda-controller2.qcow2
Examining Fedora-x86_64-20-20141008-sda-controller.qcow2 ...
◓ 25% ⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒══════════════════════════════════════════════════════⟧ --:--
 100% ⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧ 00:00
**********

Summary of changes:

/dev/sda1: This partition will be left alone.
    
    /dev/sda2: This partition will be resized from 9.5G to 39.5G.  The LVM 
    PV on /dev/sda2 will be expanded using the 'pvresize' method.
    
    /dev/fedora/root: This logical volume will be expanded to maximum size. 
     The filesystem ext4 on /dev/fedora/root will be expanded using the 
    'resize2fs' method.
    
    **********
Setting up initial partition table on Fedora-x86_64-20-20141008-sda-controller2.qcow2 ...
Copying /dev/sda1 ...

</code>

===== - Tuning lvm =====
  * https://sysadmincasts.com/episodes/27-lvm-linear-vs-striped-logical-volumes
  * http://www.redhat.com/magazine/009jul05/features/lvm2/