HOW-TO: Add Swap Space to Ubuntu/Debian

Overview

Swap space is disk-based virtual memory that allows your system to extend available RAM. When physical RAM is full, the kernel can move less-used memory pages to swap, freeing up RAM for active processes. This guide shows you how to add swap space on Ubuntu and Debian systems.

What you'll learn:

Check current swap configuration
Create a swap file (recommended for flexibility)
Create a swap partition (for fresh installations)
Enable and disable swap
Configure swappiness (swap aggressiveness)
Monitor swap usage
Troubleshoot swap performance

Why swap matters:

Prevents out-of-memory (OOM) crashes
Allows graceful degradation under load
Useful for systems with limited RAM (VPS, laptops, Raspberry Pi)
Performance trade-off: disk is slower than RAM, but something is better than nothing

Prerequisites

Check Your System

# Verify you're on Ubuntu/Debian
cat /etc/os-release | grep -E "^(NAME|VERSION)="
# Output should include: Ubuntu or Debian

# Check your current user permissions
id
# You should see "uid=0(root)" or be able to sudo

Required Permissions

All swap operations require root privileges or sudo access. You'll use sudo throughout this guide.

Verify Current Swap

# Check current swap usage
free -h
# Output example:
#                total        used        free      shared  buff/cache   available
# Mem:           3.9Gi       2.1Gi       1.3Gi      102Mi       1.2Gi       1.5Gi
# Swap:          2.0Gi       512Mi       1.5Gi

# List swap devices/files
swapon --show
# Output example:
# NAME                TYPE       SIZE   USED PRIO
# /swapfile           file      2.0G 512.0M   -2

If Swap: 0B, you have no swap configured yet.

Method 1: Create a Swap File (Recommended)

Creating a swap file is flexible, easy to resize, and doesn't require repartitioning. This is the preferred method for most users.

Step 1: Choose Swap Size

General recommendations:

Small RAM (<2GB): Swap = 2× RAM
Medium RAM (2-8GB): Swap = RAM size
Large RAM (>8GB): Swap = 0.5× to 1× RAM (optional)
Minimum: 1–2 GB swap is recommended

Examples:

512 MB RAM system → 1–2 GB swap
2 GB RAM system → 2–4 GB swap
8 GB RAM system → 4–8 GB swap

Calculate available disk space:

# Check available disk space
df -h /
# Output example:
# Filesystem      Size  Used Avail Use% Mounted on
# /dev/sda1       50G   20G   30G  40% /

Ensure you have at least 2–4 GB free space.

Step 2: Create the Swap File

Create a file that will hold swap data:

# Create a 4 GB swap file (adjust size as needed)
sudo fallocate -l 4G /swapfile

# Verify the file was created
ls -lh /swapfile
# Output: -rw-r--r-- 1 root root 4.0G Apr 10 10:00 /swapfile

Alternative (older systems):

If fallocate is unavailable, use dd:

sudo dd if=/dev/zero of=/swapfile bs=1G count=4
# count=4 means 4 GB (adjust as needed)

Step 3: Set Correct Permissions

Swap files must be readable only by root for security:

# Set permissions to 600 (read/write for owner only)
sudo chmod 600 /swapfile

# Verify permissions
ls -lh /swapfile
# Output: -rw------- 1 root root 4.0G Apr 10 10:00 /swapfile

Step 4: Format as Swap Space

Initialize the file as a Linux swap area:

# Set up the swap file
sudo mkswap /swapfile

# Output example:
# Setting up swapspace version 1.
# no label, UUID=abc123def456

Step 5: Enable Swap

Activate the swap file immediately:

# Turn on swap
sudo swapon /swapfile

# Verify it's active
swapon --show
# Output:
# NAME      TYPE  SIZE USED PRIO
# /swapfile file 4.0G   0B   -2

Step 6: Make Swap Persistent

Add the swap file to /etc/fstab so it persists after reboot:

# Backup fstab first
sudo cp /etc/fstab /etc/fstab.bak

# Add swap file entry to fstab
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

# Verify it was added
cat /etc/fstab | grep swap
# Output: /swapfile none swap sw 0 0

Step 7: Verify Persistent Configuration

Test that swap will load on reboot:

# Check the entry is correct
cat /etc/fstab | tail -5

# Verify fstab syntax is valid
sudo mount -a
# No output = success

Method 2: Create a Swap Partition

Creating a dedicated swap partition is useful when installing a fresh system or reorganizing disk layout. This method provides better performance and isolation.

Step 1: Identify Available Disk Space

# List all disks and partitions
lsblk
# Output example:
# NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
# sda      8:0    0   50G  0 disk
# ├─sda1   8:1    0   40G  0 part /
# └─sda2   8:2    0   10G  0 part [SWAP]

# Or use fdisk for detailed view
sudo fdisk -l | head -30

Important: Only proceed if you have unallocated space or can safely shrink an existing partition. Back up your data first.

Step 2: Create a New Partition

Using fdisk (interactive tool):

# Open fdisk on your target disk (example: /dev/sda)
sudo fdisk /dev/sda

# Inside fdisk, enter commands:
# n         → Create new partition
# p         → Primary (or l for logical)
# [Enter]   → Use default partition number
# [Enter]   → Use default first sector
# +4G       → Allocate 4 GB for swap (adjust size)
# t         → Change partition type
# 82        → Linux swap (or search for "swap")
# w         → Write changes and exit

Full fdisk session example:

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-104857599, default 2048): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-104857599, default 104857599): +4G

Created a new partition 1 of type 'Linux' and of size 4 GiB.

Command (m for help): t
Selected partition 1
Partition type or alias (type L to list all): 82
Changed type of partition 1 to 'Linux swap / Solaris'.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Step 3: Format the Partition as Swap

# Initialize the new partition as swap
sudo mkswap /dev/sdaX
# Replace sdaX with your partition identifier (e.g., /dev/sda3)

# Output example:
# Setting up swapspace version 1.
# no label, UUID=xyz789abc123

Step 4: Enable the Swap Partition

# Activate the partition
sudo swapon /dev/sdaX

# Verify it's active
swapon --show

Step 5: Make Swap Partition Persistent

Add the partition to /etc/fstab:

# Get the UUID of the swap partition
sudo blkid /dev/sdaX | grep -o 'UUID="[^"]*"'
# Output: UUID="abc123-def456-ghi789"

# Add to fstab (use UUID for reliability)
echo 'UUID=abc123-def456-ghi789 none swap sw 0 0' | sudo tee -a /etc/fstab

Configure Swappiness

Swappiness controls how aggressively the kernel swaps memory. Range: 0–100.

0: Avoid swapping; use only when necessary (but may cause OOM)
10–30: Minimal swapping; prefer RAM (good for modern systems)
60: Balanced (default on most systems)
100: Aggressive swapping (avoid on most systems)

Check Current Swappiness

# View current swappiness value
cat /proc/sys/vm/swappiness
# Output: 60 (typical default)

Adjust Swappiness Temporarily

# Set swappiness to 30 (less aggressive)
sudo sysctl vm.swappiness=30

# Verify change
cat /proc/sys/vm/swappiness
# Output: 30

This change is lost on reboot.

Adjust Swappiness Permanently

# Open sysctl config file
sudo nano /etc/sysctl.conf

# Add or modify this line at the end:
vm.swappiness=30

# Save (Ctrl+O, Enter, Ctrl+X in nano)

# Apply changes
sudo sysctl -p
# Output: vm.swappiness = 30

Recommended Settings

Desktop/laptop with 4+ GB RAM: swappiness = 10–20
Server with 8+ GB RAM: swappiness = 5–10
Low-memory system (VPS, Pi): swappiness = 30–60
Database servers: swappiness = 1–5 (avoid swap interference)

Monitor Swap Usage

Real-Time Swap Monitoring

# Show current swap usage in human-readable format
free -h
# Output:
#                total        used        free      shared  buff/cache   available
# Mem:           3.9Gi       2.1Gi       1.3Gi      102Mi       1.2Gi       1.5Gi
# Swap:          4.0Gi       256Mi       3.7Gi

# Watch swap usage continuously
watch -n 1 free -h
# Refreshes every 1 second (Ctrl+C to exit)

# Show detailed swap information
swapon --show

Per-Process Swap Usage

# Find which processes are using swap
for file in /proc/*/status; do
  awk '/VmSwap|Name/{printf $2 " " $3}END{print ""}' "$file" | grep -v "0 kB"
done

# Output example:
# firefox 45876 kB
# chrome 234567 kB

Swap Activity Log

# Enable swap accounting (requires kernel parameter)
cat /proc/sys/vm/swap_ratio
# If 0, swap accounting is disabled

# View swap statistics
vmstat 1 5
# Output: Shows paging in (si) and out (so) rates

Troubleshooting

Issue: "swapon: cannot open /swapfile: No such file or directory"

Cause: Swap file doesn't exist.

Solution:

# Verify the swap file exists
ls -lh /swapfile

# If missing, recreate it (see Method 1, Step 2)
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

Issue: "swapon: /swapfile: Permission denied"

Cause: Incorrect file permissions.

Solution:

# Fix permissions (must be 600)
sudo chmod 600 /swapfile

# Verify
ls -lh /swapfile
# Output: -rw------- 1 root root 4.0G

Issue: System is very slow or freezing (high swap usage)

Cause: System is using too much swap, causing disk thrashing (slow I/O).

Solutions:

Increase available RAM (hardware upgrade)
Reduce memory-heavy applications (close browsers, services)

Lower swappiness value to minimize swap use:

sudo sysctl vm.swappiness=5
sudo nano /etc/sysctl.conf  # Make permanent

Ensure disk is healthy:

sudo smartctl -a /dev/sda  # Check disk health

Issue: Swap doesn't persist after reboot

Cause: Missing or incorrect /etc/fstab entry.

Solution:

# Check fstab for swap entry
cat /etc/fstab | grep swap

# If missing, add it (use UUID for reliability):
sudo blkid | grep swap  # Find UUID
echo 'UUID=<uuid> none swap sw 0 0' | sudo tee -a /etc/fstab

# Verify fstab syntax
sudo mount -a

# Reboot and test
sudo reboot
swapon --show  # Should show your swap after boot

Issue: "Not enough space for swap file"

Cause: Not enough free disk space.

Solution:

# Check disk usage
df -h

# Free up space by:
# - Removing old log files
sudo journalctl --vacuum=50M  # Limit journal to 50 MB
# - Cleaning package manager cache
sudo apt clean && sudo apt autoclean
# - Removing temp files
sudo rm -rf /tmp/*

Issue: Cannot increase swap size

Cause: Existing swap file/partition is in use.

Solution:

Disable swap:
```
sudo swapoff -a
```
Remove old swap file or partition
Create new swap with desired size (see Method 1 or 2)
Re-enable:
```
sudo swapon -a
```

Best Practices

✅ Do:

Start with 1–2 GB minimum — provides safety buffer
Use swap files on modern systems — more flexible than partitions
Set permissions to 600 — prevents unauthorized access
Monitor usage regularly — watch for excessive swapping
Test configuration before rebooting — verify fstab syntax
Keep disk defragmented — ensures swap performance
Use UUID in fstab — more reliable than device names

❌ Don't:

Use swap on slow storage — consider SSD/NVMe for better performance
Ignore persistent configuration — swap won't survive reboot without fstab entry
Set swappiness to 0 — may cause OOM crashes
Fill swap beyond 50% — indicates memory pressure; consider RAM upgrade
Delete swap files without disabling first — causes errors
Use multiple swap devices on the same disk — no performance benefit

Verification Checklist

After completing this guide, verify your setup:

# ✓ Swap is active
free -h | grep -i swap

# ✓ Swap file/partition is listed
swapon --show

# ✓ fstab has correct entry
cat /etc/fstab | grep swap

# ✓ Swappiness is set as desired
cat /proc/sys/vm/swappiness

# ✓ Disk space is sufficient
df -h /

# ✓ System boots normally (optional, after reboot)
sudo reboot
# Then: swapon --show

All checks pass = swap is properly configured! ✅

Resources

Linux Swap Official Docs: https://wiki.debian.org/Swap
Ubuntu Swap Guide: https://help.ubuntu.com/community/SwapFaq
Kernel Swap Parameters: https://www.kernel.org/doc/html/latest/admin-guide/mm/index.html
Performance Tuning: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/performance_tuning_guide/

HOW-TO: Add Swap Space to Ubuntu/Debian

Overview

What you'll learn:

Check current swap configuration
Create a swap file (recommended for flexibility)
Create a swap partition (for fresh installations)
Enable and disable swap
Configure swappiness (swap aggressiveness)
Monitor swap usage
Troubleshoot swap performance

Why swap matters:

Prevents out-of-memory (OOM) crashes
Allows graceful degradation under load
Useful for systems with limited RAM (VPS, laptops, Raspberry Pi)
Performance trade-off: disk is slower than RAM, but something is better than nothing

Prerequisites

Check Your System

# Verify you're on Ubuntu/Debian
cat /etc/os-release | grep -E "^(NAME|VERSION)="
# Output should include: Ubuntu or Debian

# Check your current user permissions
id
# You should see "uid=0(root)" or be able to sudo

Required Permissions

All swap operations require root privileges or sudo access. You'll use sudo throughout this guide.

Verify Current Swap

# Check current swap usage
free -h
# Output example:
#                total        used        free      shared  buff/cache   available
# Mem:           3.9Gi       2.1Gi       1.3Gi      102Mi       1.2Gi       1.5Gi
# Swap:          2.0Gi       512Mi       1.5Gi

# List swap devices/files
swapon --show
# Output example:
# NAME                TYPE       SIZE   USED PRIO
# /swapfile           file      2.0G 512.0M   -2

If Swap: 0B, you have no swap configured yet.

Method 1: Create a Swap File (Recommended)

Creating a swap file is flexible, easy to resize, and doesn't require repartitioning. This is the preferred method for most users.

Step 1: Choose Swap Size

General recommendations:

Small RAM (<2GB): Swap = 2× RAM
Medium RAM (2-8GB): Swap = RAM size
Large RAM (>8GB): Swap = 0.5× to 1× RAM (optional)
Minimum: 1–2 GB swap is recommended

Examples:

512 MB RAM system → 1–2 GB swap
2 GB RAM system → 2–4 GB swap
8 GB RAM system → 4–8 GB swap

Calculate available disk space:

# Check available disk space
df -h /
# Output example:
# Filesystem      Size  Used Avail Use% Mounted on
# /dev/sda1       50G   20G   30G  40% /

Ensure you have at least 2–4 GB free space.

Step 2: Create the Swap File

Create a file that will hold swap data:

# Create a 4 GB swap file (adjust size as needed)
sudo fallocate -l 4G /swapfile

# Verify the file was created
ls -lh /swapfile
# Output: -rw-r--r-- 1 root root 4.0G Apr 10 10:00 /swapfile

Alternative (older systems):

If fallocate is unavailable, use dd:

sudo dd if=/dev/zero of=/swapfile bs=1G count=4
# count=4 means 4 GB (adjust as needed)

Step 3: Set Correct Permissions

Swap files must be readable only by root for security:

# Set permissions to 600 (read/write for owner only)
sudo chmod 600 /swapfile

# Verify permissions
ls -lh /swapfile
# Output: -rw------- 1 root root 4.0G Apr 10 10:00 /swapfile

Step 4: Format as Swap Space

Initialize the file as a Linux swap area:

# Set up the swap file
sudo mkswap /swapfile

# Output example:
# Setting up swapspace version 1.
# no label, UUID=abc123def456

Step 5: Enable Swap

Activate the swap file immediately:

# Turn on swap
sudo swapon /swapfile

# Verify it's active
swapon --show
# Output:
# NAME      TYPE  SIZE USED PRIO
# /swapfile file 4.0G   0B   -2

Step 6: Make Swap Persistent

Add the swap file to /etc/fstab so it persists after reboot:

# Backup fstab first
sudo cp /etc/fstab /etc/fstab.bak

# Add swap file entry to fstab
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

# Verify it was added
cat /etc/fstab | grep swap
# Output: /swapfile none swap sw 0 0

Step 7: Verify Persistent Configuration

Test that swap will load on reboot:

# Check the entry is correct
cat /etc/fstab | tail -5

# Verify fstab syntax is valid
sudo mount -a
# No output = success

Method 2: Create a Swap Partition

Creating a dedicated swap partition is useful when installing a fresh system or reorganizing disk layout. This method provides better performance and isolation.

Step 1: Identify Available Disk Space

# List all disks and partitions
lsblk
# Output example:
# NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
# sda      8:0    0   50G  0 disk
# ├─sda1   8:1    0   40G  0 part /
# └─sda2   8:2    0   10G  0 part [SWAP]

# Or use fdisk for detailed view
sudo fdisk -l | head -30

Important: Only proceed if you have unallocated space or can safely shrink an existing partition. Back up your data first.

Step 2: Create a New Partition

Using fdisk (interactive tool):

# Open fdisk on your target disk (example: /dev/sda)
sudo fdisk /dev/sda

# Inside fdisk, enter commands:
# n         → Create new partition
# p         → Primary (or l for logical)
# [Enter]   → Use default partition number
# [Enter]   → Use default first sector
# +4G       → Allocate 4 GB for swap (adjust size)
# t         → Change partition type
# 82        → Linux swap (or search for "swap")
# w         → Write changes and exit

Full fdisk session example:

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-104857599, default 2048): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-104857599, default 104857599): +4G

Created a new partition 1 of type 'Linux' and of size 4 GiB.

Command (m for help): t
Selected partition 1
Partition type or alias (type L to list all): 82
Changed type of partition 1 to 'Linux swap / Solaris'.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Step 3: Format the Partition as Swap

# Initialize the new partition as swap
sudo mkswap /dev/sdaX
# Replace sdaX with your partition identifier (e.g., /dev/sda3)

# Output example:
# Setting up swapspace version 1.
# no label, UUID=xyz789abc123

Step 4: Enable the Swap Partition

# Activate the partition
sudo swapon /dev/sdaX

# Verify it's active
swapon --show

Step 5: Make Swap Partition Persistent

Add the partition to /etc/fstab:

# Get the UUID of the swap partition
sudo blkid /dev/sdaX | grep -o 'UUID="[^"]*"'
# Output: UUID="abc123-def456-ghi789"

# Add to fstab (use UUID for reliability)
echo 'UUID=abc123-def456-ghi789 none swap sw 0 0' | sudo tee -a /etc/fstab

Configure Swappiness

Swappiness controls how aggressively the kernel swaps memory. Range: 0–100.

0: Avoid swapping; use only when necessary (but may cause OOM)
10–30: Minimal swapping; prefer RAM (good for modern systems)
60: Balanced (default on most systems)
100: Aggressive swapping (avoid on most systems)

Check Current Swappiness

# View current swappiness value
cat /proc/sys/vm/swappiness
# Output: 60 (typical default)

Adjust Swappiness Temporarily

# Set swappiness to 30 (less aggressive)
sudo sysctl vm.swappiness=30

# Verify change
cat /proc/sys/vm/swappiness
# Output: 30

This change is lost on reboot.

Adjust Swappiness Permanently

# Open sysctl config file
sudo nano /etc/sysctl.conf

# Add or modify this line at the end:
vm.swappiness=30

# Save (Ctrl+O, Enter, Ctrl+X in nano)

# Apply changes
sudo sysctl -p
# Output: vm.swappiness = 30

Recommended Settings

Desktop/laptop with 4+ GB RAM: swappiness = 10–20
Server with 8+ GB RAM: swappiness = 5–10
Low-memory system (VPS, Pi): swappiness = 30–60
Database servers: swappiness = 1–5 (avoid swap interference)

Monitor Swap Usage

Real-Time Swap Monitoring

# Show current swap usage in human-readable format
free -h
# Output:
#                total        used        free      shared  buff/cache   available
# Mem:           3.9Gi       2.1Gi       1.3Gi      102Mi       1.2Gi       1.5Gi
# Swap:          4.0Gi       256Mi       3.7Gi

# Watch swap usage continuously
watch -n 1 free -h
# Refreshes every 1 second (Ctrl+C to exit)

# Show detailed swap information
swapon --show

Per-Process Swap Usage

# Find which processes are using swap
for file in /proc/*/status; do
  awk '/VmSwap|Name/{printf $2 " " $3}END{print ""}' "$file" | grep -v "0 kB"
done

# Output example:
# firefox 45876 kB
# chrome 234567 kB

Swap Activity Log

# Enable swap accounting (requires kernel parameter)
cat /proc/sys/vm/swap_ratio
# If 0, swap accounting is disabled

# View swap statistics
vmstat 1 5
# Output: Shows paging in (si) and out (so) rates

Troubleshooting

Issue: "swapon: cannot open /swapfile: No such file or directory"

Cause: Swap file doesn't exist.

Solution:

# Verify the swap file exists
ls -lh /swapfile

# If missing, recreate it (see Method 1, Step 2)
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

Issue: "swapon: /swapfile: Permission denied"

Cause: Incorrect file permissions.

Solution:

# Fix permissions (must be 600)
sudo chmod 600 /swapfile

# Verify
ls -lh /swapfile
# Output: -rw------- 1 root root 4.0G

Issue: System is very slow or freezing (high swap usage)

Cause: System is using too much swap, causing disk thrashing (slow I/O).

Solutions:

Increase available RAM (hardware upgrade)
Reduce memory-heavy applications (close browsers, services)

Lower swappiness value to minimize swap use:

sudo sysctl vm.swappiness=5
sudo nano /etc/sysctl.conf  # Make permanent

Ensure disk is healthy:

sudo smartctl -a /dev/sda  # Check disk health

Issue: Swap doesn't persist after reboot

Cause: Missing or incorrect /etc/fstab entry.

Solution:

# Check fstab for swap entry
cat /etc/fstab | grep swap

# If missing, add it (use UUID for reliability):
sudo blkid | grep swap  # Find UUID
echo 'UUID=<uuid> none swap sw 0 0' | sudo tee -a /etc/fstab

# Verify fstab syntax
sudo mount -a

# Reboot and test
sudo reboot
swapon --show  # Should show your swap after boot

Issue: "Not enough space for swap file"

Cause: Not enough free disk space.

Solution:

# Check disk usage
df -h

# Free up space by:
# - Removing old log files
sudo journalctl --vacuum=50M  # Limit journal to 50 MB
# - Cleaning package manager cache
sudo apt clean && sudo apt autoclean
# - Removing temp files
sudo rm -rf /tmp/*

Issue: Cannot increase swap size

Cause: Existing swap file/partition is in use.

Solution:

Disable swap:
```
sudo swapoff -a
```
Remove old swap file or partition
Create new swap with desired size (see Method 1 or 2)
Re-enable:
```
sudo swapon -a
```

Best Practices

✅ Do:

Start with 1–2 GB minimum — provides safety buffer
Use swap files on modern systems — more flexible than partitions
Set permissions to 600 — prevents unauthorized access
Monitor usage regularly — watch for excessive swapping
Test configuration before rebooting — verify fstab syntax
Keep disk defragmented — ensures swap performance
Use UUID in fstab — more reliable than device names

❌ Don't:

Use swap on slow storage — consider SSD/NVMe for better performance
Ignore persistent configuration — swap won't survive reboot without fstab entry
Set swappiness to 0 — may cause OOM crashes
Fill swap beyond 50% — indicates memory pressure; consider RAM upgrade
Delete swap files without disabling first — causes errors
Use multiple swap devices on the same disk — no performance benefit

Verification Checklist

After completing this guide, verify your setup:

# ✓ Swap is active
free -h | grep -i swap

# ✓ Swap file/partition is listed
swapon --show

# ✓ fstab has correct entry
cat /etc/fstab | grep swap

# ✓ Swappiness is set as desired
cat /proc/sys/vm/swappiness

# ✓ Disk space is sufficient
df -h /

# ✓ System boots normally (optional, after reboot)
sudo reboot
# Then: swapon --show

All checks pass = swap is properly configured! ✅

Resources

Linux Swap Official Docs: https://wiki.debian.org/Swap
Ubuntu Swap Guide: https://help.ubuntu.com/community/SwapFaq
Kernel Swap Parameters: https://www.kernel.org/doc/html/latest/admin-guide/mm/index.html
Performance Tuning: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/performance_tuning_guide/

HOW-TO: Add Swap Space to Ubuntu/Debian

Overview

Prerequisites

Check Your System

Required Permissions

Verify Current Swap

Method 1: Create a Swap File (Recommended)

Step 1: Choose Swap Size

Step 2: Create the Swap File

Step 3: Set Correct Permissions

Step 4: Format as Swap Space

Step 5: Enable Swap

Step 6: Make Swap Persistent

Step 7: Verify Persistent Configuration

Method 2: Create a Swap Partition

Step 1: Identify Available Disk Space

Step 2: Create a New Partition

Step 3: Format the Partition as Swap

Step 4: Enable the Swap Partition

Step 5: Make Swap Partition Persistent

Configure Swappiness

Check Current Swappiness

Adjust Swappiness Temporarily

Adjust Swappiness Permanently

Recommended Settings

Monitor Swap Usage

Real-Time Swap Monitoring

Per-Process Swap Usage

Swap Activity Log

Troubleshooting

Issue: "swapon: cannot open /swapfile: No such file or directory"

Issue: "swapon: /swapfile: Permission denied"

Issue: System is very slow or freezing (high swap usage)

Issue: Swap doesn't persist after reboot

Issue: "Not enough space for swap file"

Issue: Cannot increase swap size

Best Practices

✅ Do:

❌ Don't:

Verification Checklist

Resources

See Also

🔗 Referenced by

HOW-TO: Add Swap Space to Ubuntu/Debian

Overview

Prerequisites

Check Your System

Required Permissions

Verify Current Swap

Method 1: Create a Swap File (Recommended)

Step 1: Choose Swap Size

Step 2: Create the Swap File

Step 3: Set Correct Permissions

Step 4: Format as Swap Space

Step 5: Enable Swap

Step 6: Make Swap Persistent

Step 7: Verify Persistent Configuration

Method 2: Create a Swap Partition

Step 1: Identify Available Disk Space

Step 2: Create a New Partition

Step 3: Format the Partition as Swap

Step 4: Enable the Swap Partition

Step 5: Make Swap Partition Persistent

Configure Swappiness

Check Current Swappiness

Adjust Swappiness Temporarily

Adjust Swappiness Permanently

Recommended Settings

Monitor Swap Usage

Real-Time Swap Monitoring

Per-Process Swap Usage

Swap Activity Log

Troubleshooting

Issue: "swapon: cannot open /swapfile: No such file or directory"

Issue: "swapon: /swapfile: Permission denied"

Issue: System is very slow or freezing (high swap usage)

Issue: Swap doesn't persist after reboot

Issue: "Not enough space for swap file"

Issue: Cannot increase swap size

Best Practices