Fix "Cannot Allocate Memory"

Understanding the Error

System has no available memory for new process/request.

Check Memory Status

free -h
cat /proc/meminfo
sudo dmesg | tail -20 | grep -i "out of memory"

Fix 1: Kill Memory-Hogging Processes

# Find top memory users
ps aux --sort=-%mem | head -10

# Kill process
sudo kill -9 PID

Fix 2: Add Swap Space

# Create 2GB swap
sudo fallocate -l 2G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

# Make permanent
echo "/swapfile none swap sw 0 0" | sudo tee -a /etc/fstab

Fix 3: Enable Overcommit Memory

sudo sysctl -w vm.overcommit_memory=1
sudo sysctl -w vm.overcommit_ratio=90
echo "vm.overcommit_memory=1" >> /etc/sysctl.conf

Fix 4: Reduce Application Memory Usage

• PHP: Lower memory_limit
• MySQL: Reduce buffer pool
• Apache: Reduce MaxClients
• Node.js: Use --max-old-space-size

Fix 5: Clear Caches

sudo sync && echo 3 > /proc/sys/vm/drop_caches

Fix 6: Check for Memory Leak

# Monitor over time
watch -n 5 "ps aux --sort=-%mem | head -5"
# If memory grows continuously, find and fix leak

Prevent Future Issues

# Monitor memory alerts
0 * * * * free -h | awk 'NR==2{if($7<200) system("echo Low memory | mail -s Alert admin@example.com")}'