The Perceptus Back Story

My adventurous rebuild of my home server continues.

I made a mistake when rebuilding my VMWare Server virtual machine, I used the default 8GB partition size, which is too small, even though it only holds work files for a couple of users.

I had most things back up and running, so it was time to fix my disk space error.  This turned into a crash course in Logical Volume Manager (LVM).

DISCLAIMER: I take no responsibility for any actions that you take on your own systems.  As I mentioned, this is all new to me, and it is very possible that I have made mistakes. Follow at your own risk. I’m not even sure that I have all the terminology correct.

The following are somewhat edited  notes that I took as I went along.

First, some terminology, mostly from: http://www.linux-tutorial.info/modules.php?name=Howto&pagename=LVM-HOWTO/vg.html

• LVM abstracts disk space as seen by the operating system from physical disks.
• A Volume Group is the highest level abstraction used within the LVM. It gathers together a collection of Logical Volumes and Physical Volumes into one administrative unit. (This is an extra level of organization than you might be used to… you might put all SSDs in one VG and all HDDs in a separate one to make it easier to keep track.)
• A physical volume is typically a hard disk, though it may well just be a device that ‘looks’ like a hard disk (eg. a software raid device).
• LV = Equivalent of a disk partition in a non-LVM system. The LV is visible as a standard block device; as such the LV can contain a file system (eg. /home).

General overview:  Create disk space in VMWare (or add physical disk space in a non virtualized environment).  Create a new partition. Join that partition to a Logical Volume to make the Logical Volume larger. Expand the Linux partition to fill it’s now bigger Logical Volume.

The steps that I took:

• Expand the VMWare virtual disk with the VMWare tool (Google for it).  The non-VM equivalent would be to clone an old, smaller drive onto a new, larger drive.
• create a new disk partition on the VMWare “physical” disk.
  • /sbin/fdisk /dev/sda
  • n [new]
  • p [primary – I wonder if E would have been a better long term choice]
  • 3 [I think there are two already]
  • defaults for size
  • w [write]
  • /sbin/shutdown -r now
• create the physical partition (LVM)
  • /sbin/pvcreate /dev/sda3
• that worked:

# df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/main-root20G  6.3G   12G  35% /

/dev/md1               99M   16M   78M  18% /bootnone                  125M     0  125M   0% /dev/shm