Fixing “InnoDB: Error: log file ./ib_logfile0 is of different size”

For the last few days I’ve been moving MySQL databases around at work.  Being a bit in a rush and overconfident (I have backups!),  I was simply detaching the /var/lib/mysql volume on one host (running Amazon AMI and MySQL) and attaching it to another host (running CentOS 7 and MariaDB).

It’s not surprising that I got this error: “InnoDB: Error: log file ./ib_logfile0 is of different size“.  Gladly, this ServerFault thread provided enough hints for me to solve the problem.  In a nutshell:

1. Temporarily comment out the InnoDB log file size setting (e.g.: innodb_log_file_size = 64M) in /etc/my.cnf.
2. Set innodb_fast_shutdown to 0 (read more).
3. Restart the MySQL service once or twice.
4. Uncomment the log file size setting.
5. Set InnoDB fast shutdown back to default or remove it from your my.cnf altogether.
6. Celebrate!

Knowing how little I learn from my own mistakes, I’m sure I’ll find this post useful in the future.