Create and remove swap files in Ubuntu

There are two basic types of memory: Random Access Memory (RAM) and swap files.

Computers use RAM to store data and to run programs and services. Because this data is not
stored when you turn the computer off, the allocation is only temporary allocation.

When you use a hard drive, classified as an electro-mechanical data storage device, to
store data permanently in a computer, you can save data in your system in a swap file even
when the device is off. When the computer reboots, it transfers data to RAM so the CPU can
run programs and services as needed.

The system also creates swap files to use disk space when it needs to allocate data for
kernel memory management but is out of RAM.

Usually, you use swap files in low-RAM systems (around 1 GB). You don’t necessarily
need swap files to run in a Ubuntu® operating system or Linux® environment. However,
without swap files, your system might experience degraded performance when running
high-demand programs and processes.

Recommended swap file size based on RAM

The following table shows the recommended swap sized based on how much RAM you have and
whether you choose hibernation. Hibernation requires more space because it saves the system state
when you shut down and restores the system state when you restart.

RAM Size	Swap size (without hibernation)	Swap size (with hibernation)
256MB	256MB	512MB
512MB	512MB	1GB
1GB	1GB	2GB
2GB	1GB	3GB
3GB	2GB	5GB
4GB	2GB	6GB
6GB	2GB	8GB
8GB	3GB	11GB

Create a swap file

Verify the current swap file size. You can use any of the following commands to determine the size of the existing swap file:
```
 free -m

 swapon -s

 swapon -show
```
Note: If there’s no output or the output is 000, the swap file might not be configured.
To create the swap file, run the following command:
```
dd if=/dev/zero of=/swapfile bs=1024 count=1048576
```
Where:
- if: input file (will always be the same)
- of: output file (you can name this file as you want)
- bs: block size (keep value at 1024)
- count: amount of blocks to read and write, which helps you determine how
  much space you need for the swap file.
Note: Remember that if you require a specific size, you can modify the count value by multiplying it by the block size value for the new size (in MB).
For example, multiplying the old block size, 1024, by the new size, 4096, results in 4194304 for the count.
Provide the root user with read and write permissions for the swap file by running the following command:
```
 chmod 600 /swapfile
```
Set up the swap area:
```
mkswap /swapfile
```
Use a text editor to add the line /swapfile swap swap defaults 0 0 to the /etc/fstab file.
Activate swap file (this will also test your fstab to ensure you have the correct syntax)
```
swapon -a 
```
If you do not want your swap file to survive a reboot (but be careful leaving a big file lingering about), you can skip step 5 and step 6, and just use swapon /swapfile
Verify that the new swap file configuration using any of the commands in step 1.

For more information on fstab, visit: https://wiki.archlinux.org/index.php/Fstab

Remove a swap file

Run the following command to reactivate the swap file:
```
swapoff -v /swapfile
```
Use a text editor to remove the /etc/fstab entry.
Run the following command to remove the swapfile:
```
rm -f /swapfile
```

Updated 1 day ago