Mysql – Corrupt MySQL log file – cannot start the database

Yes it is safe to delete the log file once mysqld has been shutdown

In light of this, just perform the following steps:

mysql -uroot -p... -e"SET GLOBAL innodb_fast_shutdown = 0"
service mysql stop
mv /var/lib/mysql/ib_logfile[01] /tmp
service mysql start

Starting up mysqld will recreate ib_logfile0 and ib_logfile1

Give it a Try !!!

UPDATE 2011-10-20 16:40 EDT

It cleanly page out all data in the InnoDB Buffer Pool prior to redoing the Log Files, you should set this option about 1 hour before shutdown:

SET GLOBAL innodb_max_dirty_pages_pct = 0;

By default, innodb_max_dirty_pages_pct is 75 (MySQL 5.5+) or 90 (prior to MySQL 5.5). Setting this to zero keeps the number of dirty pages under 1% of the InnoDB Buffer Pool. Performing service mysql stop does this anyway. In addition, a shutdown will finish up any remaining items in the redo log. To keep to this option just add it to /etc/my.cnf:

[mysqld]
innodb_max_dirty_pages_pct = 0

UPDATE 2013-04-19 16:16 EDT

I updated my answer a little more with innodb_fast_shutdown because I used to restart mysql and stop mysql to do this. Now, this one-step is vital because every transaction uncommitted may have other moving parts within and outside of the InnoDB Transaction Logs (See InnoDB Infrastructure).

Please note that setting innodb_fast_shutdown to 2 would clean the logs out as well but more moving parts still exist and gets picked on Crash Recovery during mysqld's startup. Setting of 0 is best.

The two answers given from @RickJames and @drogart are essentially the remedies. (+1 for each).

Right from the error log you present, the last two lines say:

InnoDB: Error: log file ./ib_logfile0 is of different size 0 134217728 bytes

InnoDB: than specified in the .cnf file 0 268435456 bytes! `

At that point, it was evident that you set innodb_log_file_size to 256M (268435456) in my.cnf while the InnoDB Transaction Logs (ib_logfile0,ib_logfile1) were respectively 128M (134217728) each. Looking back at the link to my StackOverflow answer in your question, you had to do the following:

Step 01) Add this to my.cnf:

[mysqld]
innodb_buffer_pool_size=4G
innodb_log_file_size=1G

Step 02) Run these command in the OS

mysql -u... -p... -e"SET GLOBAL innodb_fast_shutdown = 1"
service mysql stop
rm -f /var/lib/mysql/ib_logfile*
service mysql start

So as to have confidence in what is happening, run tail -f against the error log. You will see message telling you when each innodb log file is being created.