Advanced Ubuntu Server Hardening & Optimization

1. Time Zone Configuration

Why Time Zone Matters

Setting your server's time zone to match your local time is crucial for several reasons:

• Accurate Task Scheduling: Tasks trigger at exact specified times
• Simplified Management: Eliminates confusion and constant time conversion
• Log Analysis: Makes debugging and monitoring more intuitive

Check Current Time Zone

sudo timedatectl

List Available Time Zones

sudo timedatectl list-timezones

# Filter for specific region
sudo timedatectl list-timezones | grep Paris

# Filter by continent
sudo timedatectl list-timezones | grep Europe

Set Time Zone

sudo timedatectl set-timezone Europe/Paris

# Verify the change
sudo timedatectl

# Alternative verification
date

Time Zone Configuration Flow

2. Swap Space Management

Understanding Swap Space

Swap is disk space used when physical RAM is full. It acts as a safety net but is NOT a substitute for physical RAM.

Memory Hierarchy

Understanding Your Current Setup: zram

When you run sudo swapon -s and see /dev/zram0, you have zram swap instead of a traditional swap file.

Check Existing Swap

sudo swapon -s

# Alternative check with htop
htop
# Look at Swap line: Swp 0K/2.34G

Two Swap Options

Option 1: Keep zram (Recommended for Most Cases)

If your system has zram and is running fine, keep it and just optimize the settings:

# Check current swappiness
cat /proc/sys/vm/swappiness

# Set swappiness to 1 (use swap only as last resort)
sudo sysctl vm.swappiness=1

# Set cache pressure to 50
sudo sysctl vm.vfs_cache_pressure=50

# Make these permanent
sudo nano /etc/sysctl.conf

Add these lines at the end of the file:

vm.swappiness=1
vm.vfs_cache_pressure=50

Then save (Ctrl+O, Enter, Ctrl+X) and apply:

sudo sysctl -p

# Verify
cat /proc/sys/vm/swappiness
cat /proc/sys/vm/vfs_cache_pressure

Option 2: Replace zram with Traditional Swap File

Only do this if you specifically need a traditional swap file (usually not necessary).

Ubuntu Swap Size Recommendations (for Traditional Swap)

RAM Amount	Recommended Swap Size	Notes
1 GB	2 GB	2x RAM size
2-8 GB	4 GB	Equal to RAM
16-24 GB	8 GB	Half of RAM
> 24 GB	8-16 GB	Swap becomes less critical

Remove Existing Traditional Swap File (If Applicable)

# 1. Disable swap
sudo swapoff /swapfile

# 2. Backup fstab
cd /etc
sudo cp fstab fstab.back

# 3. Edit fstab and remove swap entry
sudo nano fstab
# Remove line: /swapfile swap swap defaults 0 0

# 4. Delete swap file
cd /
sudo rm /swapfile

# 5. Verify removal
sudo swapon -s
# Should return no output

# 6. Reboot to confirm
sudo reboot

Remove zram (If You Want Traditional Swap Instead)

# 1. Disable zram
sudo swapoff /dev/zram0

# 2. Remove zram package (to prevent it from restarting)
sudo apt remove zram-config

# 3. Then proceed to create traditional swap file

Create New Traditional Swap File

Formula for Block Count:

• For 2 GB: 2 × 1024 × 1024 = 2,097,152 blocks
• For 4 GB: 4 × 1024 × 1024 = 4,194,304 blocks
• For 8 GB: 8 × 1024 × 1024 = 8,388,608 blocks

# Create 2GB swap file
sudo dd if=/dev/zero of=/swapfile bs=1024 count=2097152

# Set correct permissions (only root can read/write)
sudo chmod 600 /swapfile

# Format as Linux swap
sudo mkswap /swapfile

# Activate swap
sudo swapon /swapfile

# Verify swap status
sudo swapon -s

Make Traditional Swap Permanent

# Edit fstab
cd /etc
sudo nano fstab

# Add this line at the bottom:
/swapfile swap swap defaults 0 0

# Save and reboot
sudo reboot

# After reboot, verify
sudo swapon -s
htop

Swap File Creation Process

3. Swap Configuration Parameters

Swappiness

Swappiness is a Linux kernel property (range: 0-100) that defines how aggressively the system uses swap space:

• Low value (e.g., 1): Kernel avoids swapping whenever possible
• High value (e.g., 60-100): Kernel uses swap space more aggressively

VFS Cache Pressure

VFS (Virtual File System) Cache Pressure controls the kernel's tendency to reclaim memory used for caching directory and inode objects. We set this to 50 for optimal performance.

How Swappiness and VFS Cache Pressure Work Together:

Low swappiness keeps more data in RAM → Reduces disk access → More space for VFS cache → Stores frequently used directory/file information → Improved overall performance

Configuration Commands

# Check current swappiness
cat /proc/sys/vm/swappiness

# Set swappiness to 1 (temporary)
sudo sysctl vm.swappiness=1

# Set VFS cache pressure to 50 (temporary)
sudo sysctl vm.vfs_cache_pressure=50

# Make changes permanent - edit sysctl.conf
sudo nano /etc/sysctl.conf

# Add these lines at the end:
vm.swappiness=1
vm.vfs_cache_pressure=50

# Apply changes
sudo sysctl -p

# Verify settings
cat /proc/sys/vm/swappiness
cat /proc/sys/vm/vfs_cache_pressure

Parameter Summary

Parameter	Default Value	Recommended Value	Purpose
vm.swappiness	60	1	Minimize swap usage for database performance
vm.vfs_cache_pressure	100	50	Balance between reclaiming cache and keeping it in memory

4. Practical Examples and Use Cases

Example 1: Upgrading Server RAM

Scenario: You upgrade your server from 1GB to 2GB RAM

Action Required (for traditional swap):

• Remove the existing 2GB swap file
• Create a new 4GB swap file
• Update /etc/fstab
• Reboot and verify

Action Required (for zram):

• zram automatically adjusts - no action needed
• Just verify swappiness settings are still at 1

Example 2: Restoring fstab from Backup

# Check file sizes
ls -l /etc/fstab*

# Restore from backup
sudo cp /etc/fstab.back /etc/fstab

# Verify restoration
ls -l /etc/fstab*
# Both files should now have the same size

Example 3: Monitoring Swap Usage

# Real-time monitoring with htop
htop
# Press F2 for setup, configure display columns

# Check swap usage
free -h

# Detailed swap information
sudo swapon --show

# Check if swap entry exists in fstab
cat /etc/fstab | grep swap

# If missing, add it
sudo nano /etc/fstab
# Add: /swapfile swap swap defaults 0 0

# Ensure you're using sudo
sudo dd if=/dev/zero of=/swapfile bs=1024 count=2097152

# Check if you're in the root directory
pwd
# Should output: /

# Monitor with:
vmstat 1  # to see swap activity

# Reinstall zram if you removed it and want it back
sudo apt install zram-config
sudo reboot

# Verify
sudo swapon -s

Conclusion

Advanced server hardening and optimization is essential for maintaining a secure, high-performance Ubuntu server. The topics covered in this guide provide a solid foundation for:

• Accurate time management and task scheduling
• Preventing server crashes through proper swap configuration
• Optimizing memory management for database performance
• Preparing your server for hosting stack optimization