How do I save the configuration of a cisco?

If you have a tftp server available, you can create a file on the
server for your router to write to, and then use the write network
command. From a typical unix system:

        mytftpserver$ touch /var/spool/tftpboot/myconfig
        mytftpserver$ chmod a+w /var/spool/tftpboot/myconfig

        myrouter#write net
        Remote host [10.7.0.63]? 10.7.0.2
        Name of configuration file to write [myrouter-confg]? myconfig
        Write file foobar on host 10.7.0.2? [confirm] y

Additionally, there's a Macintosh TFTP server available:

        ftp://nic.switch.ch/software/mac/peterlewis/

Additionally, you can also use expect, available from:

        ftp://ftp.uu.net/languages/tcl/expect/expect.tar.gz
        ftp://ftp.cme.nist.gov/expect/

or, in shar form from ftpeng.cisco.com.

Expect allows you to write a script which telnets to the router and
performs a ``write terminal'' command, or any other arbitrary set of
command(s), using a structured scripting language (Tcl).