In this tutorial we will learn how to create new swap file on CentOS 7 / RHEL 7. Generally on Cloud Servers ( AWS/ DigitalOcean) or VPS, swap space is not created by default. This requirement we can achieve within a few steps.
Must have free space on mounted disk. You can check by using
df -Th command.
Steps to create / add new swap file on Linux
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
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.
Paste below given content in /etc/fstab file
/swapfile-additional swap swap 0 0
5. Now mount the swap area, run below given command.
6. Enable the swap area
7. Check the number swap space mounted on your system
8. To check how much is swap space available on system.Run below given command