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

I met the same problem when I tried to run a wordpress on my micro instance without RDS.

Adding a Swap page solved the problem for me.

You can follow steps below to setup the swap space.

If it still doesn't work for you, consider using the RDS service.

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I copied the content of the blog for the record. Credit goes to the blog author pmoubed:

Amazon EC2 Micro Instance Swap Space - Linux

I have a Amazon EC2 Linux Micro instance. Since Micro instances have only 613MB of memory, MySQL crashed every now and then. After a long search about MySQL, Micro Instance and Memory Managment I found out there is no default SWAP space for Micro instance. So if you want to avoid the crash you may need to setup a swap space for your micro instance. Actually performance wise is better to enable swap.

Steps below show how to make a swap space for your Micro instance. I assume you have AWS Account with a Micro instance running.

1. Run dd if=/dev/zero of=/swapfile bs=1M count=1024
2. Run mkswap /swapfile
3. Run swapon /swapfile
4. Add this line /swapfile swap swap defaults 0 0 to /etc/fstab

Step 4 is needed if you would like to automatically enable swap file after each reboot.

Some useful command related to SWAP space:

$ swapon -s   $ free -k$ swapoff -a$ swapon  -a

References:

1. http://www.thegeekstuff.com/2010/08/how-to-add-swap-space/
2. http://cloudstory.in/2012/02/getting-the-best-out-of-amazon-ec2-micro-instances/
3. http://cloudstory.in/2012/02/adding-swap-space-to-amazon-ec2-linux-micro-instance-to-increase-the-performance/
4. http://aws.amazon.com/ec2/instance-types/

I had this problem too on an Amazon EC2 micro instance. I tried decreasing inno_db's memory usage by adding the following to /etc/my.cnf

innodb_buffer_pool_size = 64M

That didn't work, I tried dropping it down to 16M and it still didnt work. Then I realized that the instance had basically zero free memory. So I tried restarting apache

sudo system httpd restartsudo system mysqld restart

And everything worked fine. Maybe another solution is to configure apache to not eat up so much memory somehow.

It looks like you are requesting 128M of memory for the innodb_buffer_pool_size in the my.cfg file you show in the post, but MySQL thinks you are asking for 512M of memory:

Initializing buffer pool, size = 512.0M

A few lines down, the error message tells you MySQL will not start because it cannot reserve enough (512M) memory for the InnoDB buffer pool:

Fatal error: cannot allocate memory for the buffer pool

That begs three questions:

1. How much memory is on your instance? Should there be enough memory to accommodate the 512M InnoDB is trying to grab for the buffer pool, plus everything else MySQL allocates, plus your application(s), plus the operating system?
2. Why is InnoDB trying to take more than you think it should?
3. Why is MySQL restarting anyhow?

You can answer 1.

As to 2., there are a few different places MySQL option files can be located. Subsequently found files override options specified in previously found files. See

http://dev.mysql.com/doc/refman/5.5/en/option-files.html

Issue 3. could be due to an out of memory condition that occurs sometime after startup. You should see an indication of that further back in the logs if that is the case.

Finally, but somewhat unrelated, are you using EBS backed instances? That's generally highly recommended for database servers (actually, for any instance barring special circumstances). For more on that see

https://stackoverflow.com/a/3630707/141172