LVM

(Up-to-date source of this post.)

LVM is the implementation of logical volume management in Linux. As I don’t use it on a day-to-day basis, I created this blog in case I forgot the basics :-).

Terminology

       sda1   sdc       (PVs on partitions or whole disks)
          \   /
           \ /
          diskvg        (VG)
          /  |  \
         /   |   \
     usrlv rootlv varlv (LVs)
       |      |     |
    ext4  reiserfs  xfs (filesystems)

• Physical volume (PV) — partition (ex. /dev/sda1), disk (ex. /dev/sdc) or RAID device (ex. /dev/md0)
• Volume group (VG) — group of physical volumes (ex. diskvg)
• Logical volume (LV) — equivalent of standard partitions, where filesystems can be created (ex. /usrlv)

Working with LVM

Creating Volumes

1. Create PV (initialize disk)

   pvcreate /dev/md0
   

   Check the results with pvdisplay

2. Create VG

   vgcreate raid1vg /dev/md0
   

   Check the results with vgdisplay

3. Create LV

   lvcreate --name backuplv --size 50G raid1vg
   

   Check the results with lvdisplay

4. Create filesystem

   mkfs.ext3 /dev/raid1vg/backuplv
   

5. Edit /etc/fstab

   # RAID 1 + LVM
   /dev/raid1vg/backuplv   /backup        ext3    rw,noatime      0       0
   

6. Create mount point and mount volume(s)

   mkdir -p /backup
   mount -a
   

Extending LV

1. Extend the LV

   lvextend -L +5G /dev/raid1vg/backuplv
   

2. Re-size the filesystem (online re-sizing doesn’t seem to cause troubles)

   resize2fs /dev/raid1vg/backuplv