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CMG-DCM
The two main areas which need to be configured determine the different
services which the DCM provides from its serial and network ports.
Serial port services
You can use either the DCM's console or its Web configuration interface to
configure the serial data ports. The serial.x.service configuration option
determines which service each port provides.
• The simplest service is getty. This creates a console port, which you can
use to log in to the Linux operating system of the DCM directly.
• The mgetty-r service is similar, but is more suited for serial links
including modems, in which the link is not always active. This is the
default option.
• Any of the serial ports on the DCM can be directed to transmit GCF
(Güralp Compressed Format) data by setting the serial.x.service option
for that port to gcf_out. You can then run Scream! or other software on
your computer to receive the data. You will not be able to access the
Web configuration interface using this service, although you may be able
to configure attached digitizers from Scream!.
• Likewise, any serial port can be set to listen for incoming data (e.g. from
a connected digitizer or another DCM) by setting the serial.x.service
option to gcf_in. The DCM will automatically combine this data with
any other streams it is receiving, and send it on using all gcf_out ports
and any other transmission methods which have been configured.
• You can log in to the Linux operating system over a modem link by
setting the serial.x.service option to mgetty. mgetty listens for incoming
calls from your computer and sets up a login session for you. You may
need to configure minicom or hypertrm to communicate with your
own modem before you can do this.
• Both mgetty and mgetty-r can recognize incoming PPP connections and
will automatically run a PPP daemon if you attempt to connect to the
DCM in this way.
Network services
Because the DCM is a fully-fledged Linux machine, you will need to set up
networking before you can use it. Advanced networking is beyond the scope of
this manual. For a basic setup, you will need to perform the following actions:
1. Assign the DCM an IP address. By default, the DCM will try and use
DHCP (Dynamic Host Configuration Protocol) to find its own IP
address. However, this requires a DHCP server on your network. If you
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