Add swap file in linux without reboot after OS installation

In this tutorial we will learn how to add additional swap file in linux after Operating System installation without rebooting the system. There is another method of adding swap space but the condition is you should have free space in Disk partition.Means additional partition is required to create swap space.

Question: What happen when your application require more swap and you do not have free space in Disk partition or additional disk in system ?
Answer: We have another method in which we will create a blank file with desired size and create as swap and mount in system.

Now a days cloud computing is in hype and it is good to give example of Cloud Server or Instances.

ByDefault in AWS or Digital Ocean etc. the swap space is not present when you create a new instance or server in Cloud network.
This method will help you to add swap in system as well it can be use in any system (It is not cloud specific).

To create a swap file follow the given below steps

Step 1: Create a file with some size. Here in this example I am creating 1 GB means 1024 MB of file in a system

dd if=/dev/zero of=/swapfile-additional bs=1M count=1024

What is –

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 * 1024 = 1GB)

Step 2: Make the file as swap area

mkswap /swapfile-additional

Step 3: Now edit the /etc/fstab file and append the below given lines

/swapfile-additional			swap swap    0   0

Step 4: Now mount the swap area (This command helps in mounting as well as system reboot is not required after using this)

mount -a

Step 5: Enable all swap area

swapon -a

Step 6: Now check how many swap area you have in your system

swapon -s

Below is the reference of my Linux Box after hitting the “swapon -s” command. Because one swap was already present in system after addition it is showing two swap area

root@ubuntu:/# swapon -s
Filename Type Size Used Priority
/dev/mapper/ubuntu-swap_1 partition 1044476 364 -1
/swapfile-additional file 1048572 0 -2
root@ubuntu:/#

Step 7: Now verify Swap is activated or not

free -m

Below is the output of my linux system

root@ubuntu:/# free -m
total used free shared buffers cached
Mem: 1001 921 80 0 30 736
-/+ buffers/cache: 154 846
Swap: 2043 0 2043
root@ubuntu:/#