LVM: Reduce SWAP size by shrinking existing Logical Volume

LVM: Reduce SWAP size by shrinking existing Logical Volume

# Tested on RHEL 5, 6 & 7

# Check which is the swap volume and its size

root@<server>:/#> cat /etc/fstab | grep swap
/dev/rvg/swaplv         swap                    swap    defaults        0 0


root@<server>:/#> lvdisplay /dev/rvg/swaplv
  --- Logical volume ---
  LV Name                /dev/rvg/swaplv
  VG Name                rvg
  LV UUID                m0EThc-4Epd-Ecj3-lvPK-BfU0-D98H-1pgyRY
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                14.69 GB
  Current LE             470
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:5


root@<server>:/#> free -m
             total       used       free     shared    buffers     cached
Mem:         11239       4555       6683          0        422       3697
-/+ buffers/cache:        435      10803
Swap:        15039          0      15039                                     <----


root@<server>:/#> cat /proc/swaps
Filename                                Type            Size    Used    Priority
/dev/mapper/rvg-swaplv                  partition       15400952        0       -4



# Disable swapping on LV to be resized (in our case, as we have a single LV allocated to
# swap, we could run command with '-a' flag so swapping is disabled on all known swap
# devices and files (as found in /proc/swaps or /etc/fstab)

# root@<server>:/#> swapoff -a

root@<server>:/#> swapoff /dev/rvg/swaplv



# Check that swapping has been disabled

root@<server>:/#> free
             total       used       free     shared    buffers     cached
Mem:      11508864    4657068    6851796          0     432316    3786148
-/+ buffers/cache:     438604   11070260
Swap:            0          0          0                                     <----


# Reduce swap Logical Volume (we will remove 1 GB)

root@<server>:/#> lvreduce -L -1GB /dev/rvg/swaplv
  WARNING: Reducing active logical volume to 13.69 GB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce swaplv? [y/n]: y
  Reducing logical volume swaplv to 13.69 GB
  Logical volume swaplv successfully resized



# Set up the new swap area

root@<server>:/#> mkswap /dev/rvg/swaplv
Setting up swapspace version 1, size = 14696837 kB



# ------------------------------------------------------------------------------------------
# Enable swapping on resized LV (in our case, as we have a single LV allocated to swap, we
# could run command with '-a' flag so swapping is enabled on all known swap devices and
# files (as found in /proc/swaps or /etc/fstab)

# root@<server>:/#> swapon -a

root@<server>:/#> swapon /dev/rvg/swaplv


# Check final size

root@<server>:/#> free
             total       used       free     shared    buffers     cached
Mem:      11508864    4664880    6843984          0     432320    3786160
-/+ buffers/cache:     446400   11062464
Swap:     14352376          0   14352376                                       <----
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