Table 'gtid_executed' is read only


$ mysql --version
mysql Ver 14.14 Distrib 5.7.14-8, for Linux (x86_64) using 6.0

I’m trying to enable slave replication, and get the above error when running this command on the slave:

mysql> SET @@global.gtid_purged='b5180a5d-4c0e-ee19-7685-3479989fa43a:1-4';
ERROR 1036 (HY000): Table 'gtid_executed' is read only

I put “innodb-read-only = 1” in the slave /etc/my.cnf, but this is a global variable, so wouldn’t think that would be a problem.