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                                       <----