Why is my MySQL server on a micro EC2 instance crashing with \'InnoDB: mmap (x bytes) failed; errno 12,\' and how can I fix it?

"Amazon EC2, mysql aborting start because InnoDB: mmap (x bytes) failed; errno 12"

In this scenario, the MySQL server on a micro EC2 instance is repeatedly crashing with the error "InnoDB: mmap (x bytes) failed; errno 12." Despite attempts to restart the server, the issue persists. Upon examining the MySQL logs, it becomes evident that the InnoDB buffer pool initialization is failing due to insufficient memory allocation.

Understanding the Issue

The InnoDB buffer pool stores frequently accessed data in memory to optimize the performance of database operations. However, in this case, the micro instance's limited memory capacity prevents the allocation of sufficient space for the buffer pool. Consequently, InnoDB fails to initialize and the MySQL server terminates with the error message.

Configuring Swap Space

To resolve this issue, it is recommended to create a swap space, which essentially acts as additional virtual memory. This allows the operating system to utilize unused disk space as RAM, thereby increasing the available memory for critical operations like InnoDB.

Creating Swap Space

Creating a swap space involves the following steps:

1. Create a new file that will serve as the swap space:

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

2. Format the newly created file as a swap file:

mkswap /swapfile

3. Activate the swap file:

swapon /swapfile

4. To ensure the swap file persists across reboots, edit the /etc/fstab file and add the following line:

/swapfile swap swap defaults 0 0

Alternative Solution: RDS

If creating a swap space does not resolve the issue, an alternative solution is to use the Amazon RDS (Relational Database Service). RDS is a managed database service from AWS that provides dedicated database instances with guaranteed memory and storage resources. By migrating the database to an RDS instance, the issue of limited memory allocation on the micro instance can be circumvented.

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