In the another article, I discussed How to add, create a swap space on RHEL. Sometimes it can be prudent to reduce swap space after installation. For example, say you downgraded the amount of RAM in your system from 1 GB to 512 MB, but there is 2 GB of swap space still assigned. It might be advantageous to reduce the amount of swap space to 1 GB, since the larger 2 GB could be wasting disk space.
You have three options:

Remove an entire LVM2 logical volume used for swap
Remove a swap file
Reduce swap space on an existing LVM2 logical volume.

Reducing Swap on an LVM2 Logical Volume

To reduce an LVM2 swap logical volume (assuming /dev/VolGroup00/LogVol01 is the volume you want to reduce):
1. Disable swapping for the associated logical volume:

# swapo ff -v /dev/VolGroup00/LogVol01

2. Reduce the LVM2 logical volume by 512 MB:

# lvreduce /dev/VolGroup00 /LogVol01 -L -512M

3. Format the new swap space:

# mkswap /dev/VolGroup00 /LogVol01

4. Enable the extended logical volume:

# swapon -v /dev/VolGroup00/LogVol01

To test if the swap's logical volume size was successfully reduced, use cat /pro c/swaps or free to inspect the swap space.

Removing an LVM2 Logical Volume for Swap

To remove a swap volume group (assuming /d ev/Vo l G ro up0 0 /Lo g Vo l 0 2 is the swap volume you want to remove):
1. Disable swapping for the associated logical volume:

# swapoff -v /dev/VolGroup00/LogVol02

2. Remove the LVM2 logical volume of size 512 MB:
# lvremove /dev/VolGroup00/LogVol02

3. Remove the following entry from the /etc/fstab file:

/dev/VolGroup00/LogVol02 swap swap defaults 0 0

To test if the logical volume size was successfully removed, use cat /proc/swaps or free to inspect the swap space.

Removing a Swap File

To remove a swap file:
1. At a shell prompt, execute the following command to disable the swap file (where /swapfile is the swap file):

# swapoff -v /swapfile

2. Remove its entry from the /etc/fstab file.
3. Remove the actual file:

# rm /swapfile

 

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