I received the following error when I upgraded modified a slave from MySQL 5.6.14 to MariaDB 5.5.33 and executing “START SLAVE;”.

131106 11:12:31 [ERROR] Failed to open the relay log '7' (relay_log_pos 0)

I checked my relay-log.info file and it looked like below…

7
/logs/relay/hostname-relaylog.000046
661930553
hostname-masterlog.000019
661930383
0
0
0

Obviously there a difference in the relay log format, but to get this working, I removed the top line completely (the ‘7’) and I was able to start the slave successfully. Not 100% sure my slave is correctly in sync or error free so be warned of this fix / hack.