Swap

Table of Contents

What Swap Is (In Practice)

Swap is disk space that your Linux system can temporarily use as "overflow" memory when RAM is full. It is much slower than real RAM, but it:

Helps prevent crashes when you run out of RAM
Can allow you to open more applications than your RAM alone would permit
Is used for hibernation on many systems (suspend-to-disk)

Swap can be provided in two main ways:

A swap partition – a dedicated partition on disk
A swap file – a special file on an existing filesystem

In this chapter, we focus on swap as part of the installation/partitioning process.

Do You Need Swap?

Whether you need swap, and how much, depends mainly on:

How much RAM you have
What you use the machine for
Whether you want hibernation

Some typical guidelines for beginners:

Very low RAM (≤ 4 GB): swap is strongly recommended
Moderate RAM (8–16 GB): swap is still recommended, but you can use less
High RAM (≥ 32 GB): you may still want a small swap area as a safety net

For hibernation, you usually want swap size at least as large as your RAM (or very close), because the system saves the contents of RAM into swap.

How Much Swap Should You Create?

There is no universal rule, but here are practical starting points:

Desktop / laptop without hibernation:

RAM ≤ 4 GB → swap: 2–4 GB
RAM 8 GB → swap: 2–4 GB
RAM 16 GB → swap: 2–8 GB (2 GB is often enough)
RAM ≥ 32 GB → swap: 2–4 GB (or none, if you know what you’re doing)

Desktop / laptop with hibernation:

Aim for:
$$ \text{swap size} \approx \text{RAM size} $$
or slightly more, e.g. 1–2 GB extra.
Example: 8 GB RAM → 8–10 GB swap

Server / VM (beginner-friendly rule)

If RAM ≤ 8 GB → 1–2 GB swap
If RAM 8–32 GB → 2–4 GB swap
More than that depends on workload and admin preference

These are conservative, safe defaults for new users. You can adjust later as you learn more.

Swap Partition vs Swap File (At Install Time)

During installation, many distributions give you a choice between:

Creating a swap partition
Using a swap file (or letting the installer manage it automatically)

Swap Partition

A swap partition is its own partition, with no filesystem, used only for swap.

Pros:

Simple and traditional
Slightly easier for some installers and older tools
Keeps swap separate from your data

Cons:

Inflexible: changing its size later requires repartitioning
Takes up a fixed amount of disk space forever

Typical when you:

Use manual partitioning schemes (e.g., /, /home, and swap)
Want a straightforward, old-school setup

Swap File

A swap file is a regular file on an existing filesystem (often on /).

Pros:

Flexible: can resize more easily than a partition
Often created automatically by modern installers
No need to reserve a separate partition

Cons:

Slightly more complex under the hood (but installers handle this)
Historically had some limitations on certain filesystems (mostly solved now)

Many modern distributions default to a swap file on desktop/laptop installs. If you are unsure, accepting the installer’s default is usually the best choice.

Where to Put Swap

During installation, you’ll see disk layouts. Common scenarios:

Automatic partitioning

Installer creates swap automatically:

Either a swap partition, or
A swap file on the root partition

Recommended for beginners unless you have special needs.

Manual partitioning

You create partitions yourself.
For swap, you typically:

Create a new partition
Set its type to swap or Linux swap
Do not assign a mount point (swap doesn’t get mounted like / or /home)

If you plan to use a swap file instead of a partition, you can:

Skip creating a swap partition during install, and
Rely on the installer to create a swap file automatically, or set it up later.

Swap and Hibernation

If you intend to use hibernation:

Ensure your swap area (partition or file) is at least as large as your RAM.
Many distros:

Prefer using a swap partition for hibernation, but
Newer setups also support hibernating to a swap file (with some extra configuration).

When installing:

Check if the installer offers a “use swap for hibernation” or similar option.
If you care about hibernation and see such an option, enable it and follow the size recommendation it gives.

Common Installation-Time Choices

Here are some safe, simple choices for typical beginners:

Example 1: 8 GB RAM laptop, single-disk, wants hibernation

Let the installer use automatic partitioning if possible; verify it creates:

/ (root)
Maybe /home (optional)
Swap (partition or file) of 8–10 GB

If using manual partitioning:

Create swap partition of 8–10 GB
The rest of the disk for / (and /home if you want a separate one)

Example 2: 16 GB RAM desktop, no hibernation

Automatic partitioning: accept default swap setup (file or partition).
Manual partitioning:

Create swap partition of 2–4 GB
The rest goes to / (and /home if desired)

Example 3: Small VM with 2 GB RAM

Swap is important here.
1–2 GB swap is reasonable.
Automatic partitioning is usually fine; otherwise:

Create swap partition of 1–2 GB
Assign the rest to /

Things to Avoid (As a Beginner)

No swap at all on low-RAM systems

This makes running out of memory more likely and can cause sudden process kills or system instability.

Huge swap on tiny disks

Don’t allocate, for example, 20 GB swap on a 64 GB SSD if you only have 4 GB RAM and no need for hibernation.

Multiple swap partitions during install

One swap area is totally sufficient for typical beginner systems.
Extra swap can be added later if needed.

Summary

Swap is disk space used as backup memory when RAM is full.
It can be a swap partition or swap file.
For most beginners, accept the installer’s default swap configuration.
Size swap based on RAM size and whether you need hibernation.
Manual partitioning: create one partition of type swap (no mount point) if you are not using a swap file.

Comments

Please login to add a comment.

Don't have an account? Register now!