Hi, thanks both. Ok, I added the following lines to rc.local:
/sbin/modprobe slamr &> /modpErrors
/usr/sbin/slmodemd /dev/slamr0 &> /slmodErrors &
ln -s /dev/ttySL0 /dev/modem
The output of modprobe was a blank page (no errors, it seems). The output of slmodemd was the following:
error: mdm setup: cannot stat `/dev/slamr0': No such file or directory
error: cannot setup device `/dev/slamr0'
The weird thing is that when I su and do it manually after boot, it does work. Besides, after editing rc.local I don't have to execute "/sbin/modprobe slamr" after boot, just the slmodemd command. By the way, there's a space between " /usr/sbin/slmodemd" and "/dev/slamr0"