<p>The server cannot read the binary log index file because of an I/O problem, blocking startup or replication.</p>
<p>MySQL Error 1374: ER_IO_ERR_LOG_INDEX_READ occurs when the server fails to read the mysql-bin.index file, usually due to corruption, bad permissions, or disk issues. Restore or recreate the index file, fix permissions, and restart MySQL to resolve the error.</p>
I/O error reading log index file
Error 1374 appears during startup or replication when MySQL cannot read the binary log index file (mysql-bin.index). The server stops loading binary logs, halting replication and in some cases preventing startup.
The index file lists every binary log created by the server. If MySQL cannot access it, the binary logging subsystem breaks, triggering the HY000 SQL state.
File corruption is the most frequent cause. A sudden crash, power loss, or incomplete write can leave mysql-bin.index with unreadable bytes.
Incorrect file permissions or SELinux/AppArmor rules can block the mysqld process from reading the file.
Disk failures or a full filesystem can also generate I/O errors during the read operation.
First, back up the existing binary logs and their index file. Preservation protects data needed for replication recovery.
If the index file is corrupted, recreate it by listing valid binary logs manually or by running RESET MASTER to start a new binary log set.
When permissions are the issue, adjust ownership so the file is readable by the mysql user and confirm no security module is blocking access.
Server fails to start: Move the damaged mysql-bin.index aside, start MySQL, then run SHOW BINARY LOGS to rebuild the list.
Replication slave stops: Copy a fresh index file from the master or issue CHANGE MASTER TO MASTER_LOG_POS = 4 to jump to a new log file after RESET MASTER on the source.
Place MySQL data on reliable storage with battery-backed cache to reduce corruption risk.
Enable automatic filesystem checks and monitoring alerts for disk health and free space.
With Galaxy, developers can version and audit replication-related SQL such as RESET MASTER, ensuring consistent recovery procedures across environments.
Error 1595 (ER_SLAVE_FATAL_ERROR): Triggered when the slave cannot read a relay log file; fix by purging or recreating relay logs.
Error 1236 (ER_MASTER_FATAL_ERROR_READING_BINLOG): Indicates a corrupted binary log on the master; restore from backup or skip the bad event.
Unexpected shutdowns or hardware faults leave the index file in an unreadable state.
The mysql user lacks read access due to manual file moves or security policy changes.
Bad sectors, failing SSDs, or full disks prevent successful I/O operations.
The server points to a non-existent path, so mysqld cannot locate the index file.
Failure to read relay logs on a replica, often due to corruption.
Corrupted binary log on the master prevents replication.
PURGE BINARY LOGS refused because logs are still in use by replication.
It means MySQL failed to read the binary log index file (mysql-bin.index), so binary logging and replication cannot proceed.
You can move or delete it after backing up binary logs; MySQL will create a fresh index on restart, but replication positions will reset.
Stop MySQL, rename the existing index, start the server, and run SHOW BINARY LOGS to regenerate the list or RESET MASTER for a clean slate.
Galaxy tracks SQL like RESET MASTER and CHANGE MASTER in a shared workspace, so teams standardize recovery steps and reduce manual mistakes that cause index issues.
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