you can test easily enough on a local vm.
previously output of things run in rc.local went to wherever /dev/console went.
that meant if you ran 'echo hello world' from rc.local when 'console=ttyS0' on the kernel command line, you'd dsee 'hello world' on the serial console.
this is important to maintain for automated testing and I would suspect for real world use cases where people write some human friendly status or information from /etc/rc.local.
you can test easily enough on a local vm.
previously output of things run in rc.local went to wherever /dev/console went.
that meant if you ran 'echo hello world' from rc.local when 'console=ttyS0' on the kernel command line, you'd dsee 'hello world' on the serial console.
this is important to maintain for automated testing and I would suspect for real world use cases where people write some human friendly status or information from /etc/rc.local.