# Configuring swap space

Swap provides overflow memory on disk when physical RAM is exhausted. It prevents out-of-memory crashes but is significantly slower than real RAM.

## Check existing swap

```bash
swapon -s
```

{% hint style="warning" %}
If this shows an active swapfile, swap is already configured — skip to the next section.
{% endhint %}

![Example of enabled swap](https://2741608310-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUuyIBhqHgBAmQaDXz0PX%2Fuploads%2Fgit-blob-e6fddac3c7c298591f2b0f74805beb7395415251%2Fterminal-swap-swapon.png?alt=media)

## Recommended swap size

| Server RAM | Swap size |
| ---------- | --------- |
| 4 -- 16 GB | 8 GB      |
| 16+ GB     | 16 GB     |

{% hint style="info" %}
Swap is not a replacement for physical RAM. If your server constantly uses swap, upgrade memory instead.
{% endhint %}

## Create and enable swap

1. Create an 8 GB swap file:

```bash
sudo fallocate -l 8G /swapfile
```

2. Restrict permissions:

```bash
sudo chmod 600 /swapfile
```

3. Initialize and enable the swap area:

```bash
sudo mkswap /swapfile
sudo swapon /swapfile
```

4. Make swap persistent across reboots:

```bash
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
```

5. Verify swap is active:

```bash
sudo swapon --show
free -h
```

![](https://2741608310-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FUuyIBhqHgBAmQaDXz0PX%2Fuploads%2Fgit-blob-804e84ece979d8da8aeee290bd1ac1f5f50f4f02%2Fterminal-swap-show.png?alt=media)

6. Tune swap behavior:

```bash
echo 'vm.swappiness=10' | sudo tee -a /etc/sysctl.conf
echo 'vm.vfs_cache_pressure=50' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
```


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