Why is My MySQL Instance on Amazon EC2 Micro Aborting Start with \'InnoDB: mmap (x bytes) failed; errno 12\'?

Amazon EC2: Troubleshooting "mysql aborting start because InnoDB: mmap (x bytes) failed; errno 12" on Micro Instances

Micro instances on Amazon EC2 commonly experience this issue due to memory limitations. When MySQL attempts to initialize the buffer pool, it fails with an "errno 12" error. This indicates a memory allocation issue.

Cause:

Micro instances have a limited amount of RAM, and MySQL requires a significant portion for the buffer pool. Without sufficient memory, MySQL fails to start.

Solution: Enable Swap Space

Adding a swap space creates a virtual memory that acts like additional RAM. It allows the operating system to cache inactive pages, freeing up physical memory for critical processes like MySQL.

Steps:

1. Run the following command:

dd if=/dev/zero of=/swapfile bs=1M count=1024

This creates a 1GB swap file.

2. Format the swap file:

mkswap /swapfile

3. Enable the swap space:

swapon /swapfile

4. Add the following line to /etc/fstab:

/swapfile swap swap defaults 0 0

This will permanently enable the swap file.

Additional Considerations:

• Consider using Amazon's Relational Database Service (RDS) for MySQL. RDS manages database resources automatically, eliminating the need for manual configuration.
• If adding swap space does not resolve the issue, consider upgrading to a larger instance type with more RAM.

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