How to add swap virtual memory in LinuxVPS and VM

I want to install oracle10g in the virtual machine and find that the default swap space does not meet the minimum requirement. because the physical memory I allocate is 1 GB, 2 GB swap space is required as required, by default, only 1 GB of swap space is available. The steps for adding a swap space are as follows: Step 1: Make sure there is sufficient space in the system for swap space. I am using K to install oracle10g in the virtual machine, the default swap space does not meet the minimum requirements. because the physical memory I allocate is 1 GB, 2 GB swap space is required. by default, only 1 GB swap space is required. To add a swap space, follow these steps:

Step 1: Make sure that there is sufficient space in the system for swap. I am using KVM and want to add a swap file to an independent file system, add 2 GB swap file to/opt/image

Step 2: Add the swap file and set its size to 2 GB. run the following command:
[Root @ sense image] # dd if =/dev/zero of =/opt/image/swap bs = 1024 count = 2048000
After a period of time, the following results are returned:
2048000 + 0 records in
2048000 + 0 records out
2097152000 bytes (2.1 GB) copied, 272.867 seconds, 7.7 MB/s

Step 3: Create (set) the swap space and run the mkswap command.
[Root @ sense image] # mkswap/opt/image/swap
Setting up swapspace version 1, size = 2097147 kB

Step 4: Check the size of the existing swap space and run the free command.
[Root @ sense image] # free-m
Total used free shared buffers cached
Mem: 1011 989 21 0 1 875
-/+ Buffers/cache: 112 898
Swap: 1027 0 1027 or check the meminfo file
Grep SwapTotal/proc/meminfo

Step 5: Start the newly added 2 GB swap space and run the swapon command
[Root @ sense image] # swapon/opt/image/swap

Step 6: confirm that the new 2G swap space has taken effect. run the free command.
[[Root @ sense image] # free-m
Total used free shared buffers cached
Mem: 1011 995 15 0 4 877
-/+ Buffers/cache: 113 897
Swap: 3027 0 3027
Or check the meminfo file.
Grep SwapTotal/proc/meminfo

Step 7: modify the/etc/fstab file so that the newly added 2G swap space will automatically take effect after the system restarts.
Add at the end of the file:
/Opt/image/swap defaults 0 0
OK. the system's swap space is successfully added.