Why Does My MySQL on Amazon EC2 Micro Instance Abort Startup with Error 12 (Insufficient Memory)?

Amazon EC2, MySQL Aborts Startup Due to Insufficient Memory (errno 12)

When running MySQL on an Amazon EC2 micro instance, you may encounter the error "InnoDB: mmap (x bytes) failed; errno 12." This error indicates that InnoDB, the storage engine used by MySQL, is unable to allocate the necessary memory for the buffer pool due to insufficient system memory.

To resolve this issue, you can follow these steps:

1. Add Swap Space: Micro instances do not have dedicated swap space by default, which can be overcome by creating a swap file. Run the following commands:

   • dd if=/dev/zero of=/swapfile bs=1M count=1024
   • mkswap /swapfile
   • swapon /swapfile
2. Increase Buffer Pool Size: To allocate more memory for the buffer pool, increase the innodb_buffer_pool_size parameter in your MySQL configuration file (my.cnf). Ensure that the value is within the available memory range.
3. Use RDS Service: For mission-critical applications, consider using Amazon Relational Database Service (RDS), a managed database service that handles memory allocation and scaling automatically.

Example Configuration

The following is an example my.cnf configuration with increased buffer pool size and swap space:

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
symbolic-links=0
innodb_buffer_pool_size=1G

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Note: The specific value for innodb_buffer_pool_size should be adjusted based on your application's memory requirements. It should not exceed the available system memory.

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