# fdisk -l /dev/sda

Disk /dev/sda: 750.1 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1           6       48163+  de  Dell Utility
/dev/sda2   *           7        4510    36178380    7  HPFS/NTFS
/dev/sda3            4511        4771     2096482+  83  Linux
/dev/sda4            4772       91201   694248975    5  Extended
/dev/sda5            4772       91201   694248943+  8e  Linux LVM

# mount /dev/sda5 /tmp/mnt
mount: /dev/sda5 already mounted or /tmp/mnt busy

Okay, so we need to determine the volume group that contains the physical volume /dev/sda5:

# pvs
  PV         VG         Fmt  Attr PSize   PFree
  /dev/sda5  VolGroup00 lvm2 a-   662.06G 352.00M

Next, we need to list the logical volumes in VolGroup00:

# lvdisplay /dev/VolGroup00
  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol00
  VG Name                VolGroup00
  LV UUID                ThdwBX-Vj7g-Z2hE-sPq7-00v3-Pij8-6Kx7UF
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                659.78 GB
  Current LE             21113
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol01
  VG Name                VolGroup00
  LV UUID                Lxe5g6-cdyD-Se9W-FX9g-PqyC-2lI8-zYgDfe
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                1.94 GB
  Current LE             62
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1

In this example, we know that /dev/VolGroup00/LogVol00 contains the physical data that we would like to mount.  If you are unsure about what to mount on your system, look at the LV Size and compare it to the output from 'df -h' (our system output is below):

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      650G  306G  312G  50% /
/dev/sda3             2.0G   77M  1.8G   5% /boot
none                 1005M     0 1005M   0% /dev/shm

The other logical volume returned from 'lvdisplay' in our example is a swap partition, which we do not want to mount.  Here is the command for mounting the desired logical volume:

# mount /dev/VolGroup00/LogVol00 /tmp/mnt