How to Add Swap Memory in Ubuntu 24.04

Updated on June 17, 2024

Introduction

Swap memory is dedicated storage space used as virtual memory when the Random Access Memory (RAM) on your server is used up or fully utilized by actively running process. Swap memory enables the server to migrate less-used processes from RAM to the dedicated server space to free up your memory. As a result, when your server runs out of memory space, instead of crashing, additional processes are stored in your swap memory to keep the system healthy.

This article explains how to add swap memory on Ubuntu 24.04. You will set up swap memory using a dedicated file on your server storage and use Vultr Block Storage as a dedicated swap volume to increase the available server memory.

Prerequisites

Before you begin:

Deploy a Debian server on Vultr.
Deploy a Vultr Block Storage volume and attach it to the server.
Access the server using SSH as a non-root user with sudo privileges.

View Existing Swap Memory

Swap memory is available on Ubuntu 24.04 servers by default but with low dedicated space on the server. Follow the steps below to view the existing swap memory before adding new memory to the server.

View the available server memory including RAM and Swap using the free utility.

                            console
                            
$ sudo free -h

Verify the Swap memory available on your server similar to the output below.

                            console
                            
                        
total        used        free      shared  buff/cache   available
1. Mem:           955Mi       317Mi       201Mi       1.2Mi       598Mi       638Mi
1. Swap:          2.3Gi       268Ki       2.3Gi

Based on the above output, the server includes a 2GB Swap memory volume.

Create Swap Memory

Swap memory is dedicated space on a storage device such as your server storage or a block storage volume. Follow the sections below to create swap memory using either a Swapfile or a dedicated Vultr Block Storage volume on your server.

Create Swap Memory using a Swapfile

Create a new Swapfile with a specific size such as 2GB using the fallocate utility in your root directory /.
console
```
$ sudo fallocate -l 2G /swapfile.img
```
Modify the Swapfile permissions to allow only the root user to read and write changes on the file.
console
```
$ sudo chmod 0600 /swapfile.img
```
Format the file as swap using mkswap.
console
```
$ sudo mkswap /swapfile.img
```

Verify the new swam memory size, label information and UUID similar to the following output.

Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)
no label, UUID=2ed3e083-fac2-4571-bbdf-e9967aa1fc03

Create Swap Memory using Vultr Block Storage

List the storage devices available on your server using the lsblk utility. The new disk is attached as /dev/vdb and it has no partitions.
console
```
$ lsblk
```
Output:
```
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sr0     11:0    1 1024M  0 rom
vda    253:0    0   25G  0 disk
├─vda1 253:1    0  512M  0 part /boot/efi
└─vda2 253:2    0 24.5G  0 part /
vdb    253:16   0    2G  0 disk
```
The Vultr Block Storage device is attached as vdb based on the above output with a 40GB size.
Initialize the volume using the GPT partition table.
console
```
$ sudo parted -s /dev/vdb mklabel gpt
```
Create a new partition using the entire block storage volume.
console
```
$ sudo parted -s /dev/vdb unit mib mkpart primary 0% 100%
```

List the server storage devices again and verify that the new block storage partitiion is available.

console

$ lsblk

Output:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sr0     11:0    1 1024M  0 rom  
vda    253:0    0   25G  0 disk 
├─vda1 253:1    0  512M  0 part /boot/efi
└─vda2 253:2    0 24.5G  0 part /
vdb    253:16   0   40G  0 disk 
└─vdb1 253:17   0   40G  0 part

Convert the new block storage partition to swap.

                            console
                            
$ sudo mkswap /dev/vdb1

Output:

Setting up swapspace version 1, size = 40 GiB (42947571712 bytes)
no label, UUID=7b3b6fa6-b344-41bd-b25b-f8657caa36b4

View your block devices information and verify that the new swap partition is available.

console

$ blkid

Output:

/dev/vda2: UUID="95e88749-c308-4c15-aca0-f47049d0c699" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="48874572-7e1f-4766-93e7-431038bd78f3"
/dev/vda1: UUID="D587-7645" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="96ca28e5-4696-482c-9359-24b87f2ea53e"
/dev/vdb1: UUID="ca230c16-b5a4-44e6-b5a8-930bb1f33fcf" TYPE="swap" PARTLABEL="primary" PARTUUID="7897c216-dc99-4e91-be17-abc1a0dba849"

Note the swap partition UUID value to use when mounting the volume automatically at boot time.

Enable Swap Memory

Enable the Swapfile as swap memory using the swapon utility.
console
```
$ sudo swapon /swapfile.img
```

View the server swap memory and verify that the new Swapfile is active.

                            console
                            
$ sudo swapon -s

Output:

Filename                                Type            Size            Used            Priority
/swapfile                               file            2457596         268             -2
/swapfile.img                           file            2097148         0               -3

Run the following command to enable the Vultr Block Storage swap partition as swap memory. Replace /dev/vdb1 with your actual partition path.
console
```
$ sudo swapon /dev/vdb1
```

View the server swap memory and verify that the swap partition is active.

                            console
                            
$ sudo swapon -s

Output:

Filename                                Type            Size            Used            Priority
/swapfile                               file            2457596         268             -2
/swapfile.img                           file            2097148         0               -3
/dev/vdb1                               partition       41940988        0               -4

Configure the File System Table (fstab) to enable Automatic Mounting

The File System Table (fstab) configuration defines how file systems are mounted on a server. Follow the steps below to configure fstab to enable the automatic mounting of swap memory volumes on your server at boot time.

Backup the original fstab configuration on your server.
console
```
$ sudo cp /etc/fstab /etc/fstab.bak
```
Open the fstab configuration file using a text editor such as nano.
console
```
$ sudo nano /etc/fstab
```
Add the following Swapfile configuration at the end of the file.
ini
```
/swapfile.img swap swap defaults 0 0
```
Save and close the file.

The above configuration enables automatic mounting using the /swapfile.img file. Within the configuration:
- swap: Enables the swap file system type.
- swap: Sets the swap mount point.
- 0: Disables backups on the swap file system.
- 0: Disables file system checks on the swap memory.
- Add the block storage swap partition using its UUID value to enable automatic mounting on the volume.
ini
```
UUID=ca230c16-b5a4-44e6-b5a8-930bb1f33fcf       swap    swap    sw      0       0
```
You have enabled automatic mounting of swap memory on your server. The server automatically mounts and enables the swap memory at boot time.

Configure Swappiness

A Swappiness value controls how the system switches between the main memory (RAM) and swap memory on your server based on the usage percentage. A low value minimizes swapping to disk while a higher value enables the server to use swap memory based on the following ratings:

0: Enables the system to avoid swapping processes out of physical memory.
1-49: Enables swapping with reduced usage unless the main memory (RAM) is at capacity.
50: Balances swapping and memory caching on the server.
51-99: Increases swapping from the main memory to swap memory.
100: Prioritizes swapping on the server and processes are continuously moved from RAM to swap.

Follow the steps below to configure the swappiness value on your server.

Run the following command to modify the /etc/sysctl.conf with your swappiness value. Replace 50 with your desired swapping level.
console
```
$ echo "vm.swappiness = 50" | sudo tee -a /etc/sysctl.conf
```
Output:
```
vm.swappiness = 50
```
Reload the systctl configuration to apply the configuration changes.
console
```
$ sudo sysctl -p
```

Test the Swap Memory

View all available swap volumes on your server.

                            console
                            
$ sudo swapon -s

Output:

Filename                                Type            Size            Used            Priority
/swapfile                               file            2457596         268             -2
/swapfile.img                           file            2097148         0               -3
/dev/vdb1                               partition       41940988        0               -4

Run the following command to activate all inactive swap volumes in your /etc/fstab configuration.
console
```
$ sudo swapon -a
```

View your server memory and verify the amount of swap memory actively in use.

                            console
                            
$ sudo free -h

Output:

               total        used        free      shared  buff/cache   available
Mem:           955Mi       348Mi       155Mi       1.2Mi       613Mi       607Mi
Swap:           44Gi       268Ki        44Gi

Remove Swap Memory

Use the swapoff utility with the Swapfile or partition path to disable on your server. For example, run the following command to disable the default Swapfile /swapfile.
console
```
$ sudo swapoff /swapfile
```

View the swap volumes on your server and verify that the default Swapfile is disabled.

                            console
                            
$ sudo swapon -s

Output:

Filename                                Type            Size            Used            Priority
/swapfile.img                           file            2097148         0               -2
/dev/vdb1                               partition       41940988        0               -3

Conclusion

You have added swap memory on an Ubuntu 24.04 server and extended the default system memory to enable swapping. Swap memory may be slower as compared to RAM but improves your server performance by offloading resource-intensive processes from the main memory. For more configuration options, run $ man swapon to view the swap commands manual.

How to Add Swap Memory in Ubuntu 24.04

Introduction

Prerequisites

View Existing Swap Memory

Create Swap Memory

Create Swap Memory using a Swapfile

Create Swap Memory using Vultr Block Storage

Enable Swap Memory

Configure the File System Table (fstab) to enable Automatic Mounting

Configure Swappiness

Test the Swap Memory

Remove Swap Memory

Conclusion

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Features

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Resources

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