passing --single-transaction in mysqldump command line tool
Sure enough, --single-transaction is supported from the MySQL command line.

mysqldump --single-transaction databasename


Will use all of the default options from --opt (except for --lock-tables, which is overridden by --single-transaction) as well as --single-transaction.

That really should be all there is to it.

I recommend briefly reading through all of the options of mysqldump - you may find that some of them, like --routines, are important for your database.