> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Design Hard Disk Layout Manage Swap Space

> This article explains how to configure and manage swap space in Linux, covering swap partitions and files with step-by-step examples.

In this lesson we’ll explore how to configure and manage swap space in Linux. Swap is a dedicated area on disk where the kernel moves inactive pages from RAM when physical memory is exhausted. We’ll cover both swap partitions and swap files, with step-by-step examples.

## Understanding Swap with a Simple Scenario

Imagine a system with 4 GiB of RAM:

* A video editor consumes 2 GiB.
* An audio editor consumes another 2 GiB.

At this point, RAM is full. With a 2 GiB swap partition, Linux can relocate the idle video editor’s memory pages to swap, freeing up 2 GiB of RAM for a new application such as Chrome.

<Frame>
  ![The image illustrates the concept of managing swap space, showing a 4GB RAM with 2GB used by an audio editor and Chrome, and a 2GB swap partition used by a video editor.](https://kodekloud.com/kk-media/image/upload/v1752881425/notes-assets/images/Linux-Professional-Institute-LPIC-1-Exam-101-Design-Hard-Disk-Layout-Manage-Swap-Space/managing-swap-space-ram-usage-diagram.jpg)
</Frame>

<Callout icon="lightbulb" color="#1CB2FE">
  Swap space is much slower than RAM. Use it as overflow memory, not as a substitute for adequate physical RAM.
</Callout>

## Checking Existing Swap

List active swap areas:

```bash theme={null}
swapon --show
```

Inspect block devices and partitions:

```bash theme={null}
lsblk
```

Example output:

```bash theme={null}
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda      8:0    0   20G  0 disk 
├─vda1   8:1    0    1G  0 part /boot
├─vda2   8:2    0   19G  0 part 
│ ├─cs-root 253:0 0   17G  0 lvm  /
│ └─cs-swap 253:1 0    2G  0 lvm  [SWAP]
vdb      8:16   0   10G  0 disk 
├─vdb1   8:17   0    1G  0 part 
├─vdb2   8:18   0    4G  0 part 
└─vdb3   8:19   0    2G  0 part
```

In this example, `/dev/vdb3` is reserved for swap but not yet active.

## Command Reference

| Task                         | Command                                          |
| ---------------------------- | ------------------------------------------------ |
| List active swap             | `swapon --show`                                  |
| List block devices           | `lsblk`                                          |
| Format a swap partition      | `sudo mkswap /dev/vdb3`                          |
| Enable a swap area           | `sudo swapon --verbose /dev/vdb3`                |
| Disable a swap area          | `sudo swapoff /dev/vdb3`                         |
| Create a swap file (2 GiB)   | `sudo dd if=/dev/zero of=/swap bs=1M count=2048` |
| Secure swap file permissions | `sudo chmod 600 /swap`                           |
| Format a swap file           | `sudo mkswap /swap`                              |
| Enable swap file             | `sudo swapon --verbose /swap`                    |

## Creating and Enabling a Swap Partition

1. Format the partition:

   ```bash theme={null}
   sudo mkswap /dev/vdb3
   ```

2. Activate it immediately:

   ```bash theme={null}
   sudo swapon --verbose /dev/vdb3
   ```

3. Verify it’s active:

   ```bash theme={null}
   swapon --show
   ```

4. Make it persistent by adding to `/etc/fstab`:

   ```text theme={null}
   /dev/vdb3 none swap sw 0 0
   ```

## Disabling Swap

To turn off a swap partition or file:

```bash theme={null}
sudo swapoff /dev/vdb3
```

## Creating and Using a Swap File

If you cannot repartition the disk, create a swap file instead:

1. Create a zero-filled file (2 GiB):

   ```bash theme={null}
   sudo dd if=/dev/zero of=/swap bs=1M count=2048 status=progress
   ```

2. Restrict permissions:

   ```bash theme={null}
   sudo chmod 600 /swap
   ```

3. Format the file as swap:

   ```bash theme={null}
   sudo mkswap /swap
   ```

4. Enable the swap file:

   ```bash theme={null}
   sudo swapon --verbose /swap
   ```

5. Persist across reboots by adding to `/etc/fstab`:

   ```text theme={null}
   /swap none swap sw 0 0
   ```

<Callout icon="triangle-alert" color="#FF6B6B">
  Excessive swapping (thrashing) can severely degrade performance. Monitor swap usage with `free -h`, `vmstat`, or `htop`.
</Callout>

## Links and References

* [Linux Swap FAQs](https://tldp.org/LDP/swap-guide/)
* [swapon(8) Manual](https://man7.org/linux/man-pages/man8/swapon.8.html)
* [lsblk(8) Manual](https://man7.org/linux/man-pages/man8/lsblk.8.html)
* [Filesystem Hierarchy Standard](https://refspecs.linuxfoundation.org/FHS_3.0/fhs/index.html)

Practice these commands to master swap space management on Linux.

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