Trouble running toolkit on live table


I’m trying to use percona toolkit to do a schema change on an active live table, and I’m having trouble at the creating triggers stage.

I’m running (something like)

pt-online-schema-change --max-lag 100000 --execute --alter “column_name int” t=table

Which kind of troubles?
Do you already have triggers for that table?
Could you share the error message, the output of the SHOW CREATE TABLE <your_tablename_here>, and the triggers?