How to increase Swap Memory in CentOS 7?

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In the terminal, on giving free -m command, I was able to see that my swap space in the memory was just 2048 MB. But for my work and for Oracle database I need to increase the swap space. I have enough memory space. How can I do that? Please let me know.

Oct 5, 2018 in Linux Administration by Neha
• 6,280 points
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1 answer to this question.

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Follow the below steps and procedures:

Prerequisites

Must have free space on mounted disk. You can check by using df -Th command.

Next follow these:

1. Create swapfile-additional file with dd command in / (root). You can select any other partition but it should be mounted (For eg. /opt, /usr ,/NewMountedPartition)

dd if=/dev/zero of=/swapfile-additional bs=1M count=4048

dd = It is a unix command used for convert and copy a file
if = read from FILE instead of stdin
/dev/zero = /dev/zero is a special file in Unix-like operating systems that provides as many null characters (ASCII NUL, 0x00) as are read from it
of = write to FILE instead of stdout
/swapfile-additional = file named swapfile-additional will be created in /
bs = Read and write bytes at a time but if you do not mention MB or GB like only number it will read as bytes. for eg. bs=1024 means 1024 bytes
count = Copy input blocks in our case it is 1024 (1M * 4048 = 4GB)

2. Run mkswap command to make swap area

mkswap /swapfile-additional

3. Change the permission of file swapfile-additional

chmod 600 /swapfile-additional

4. Permanent mounting the swap space by editing the /etc/fstab file .
Use your file editor, I generally use vi editor.

vi /etc/fstab

Paste below given content in /etc/fstab file

/swapfile-additional swap swap    0   0

5. Now mount the swap area, run below given command.

mount -a

6. Enable the swap area

swapon -a

7. Check the number swap space mounted on your system

swapon -s

8. To check how much is swap space available on system. Run below given command

free -m
answered Oct 5, 2018 by Frankie
• 9,810 points

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