Yes of course, you schedule a file system backup job and give the database "include path /". Same for any mount points "include path /ua01", so you could have a dataset that looks something like :
include host myserver
include path /
include path /var
include path /ua01
Now it's important to remember that this is not an image backup, so you won't be able to restore a dead OS using this backup, there will be files changing and locked during the backup. A DR approach would be to reimage the OS, install OSB and restore the config files you need back, quite specifically. You would never tell it to restore /, or /etc or anything like that.