Guralp Systems CMG-DCM - Manual (Page 50)

CMG-DCM Data Communications Module
has the format
key-id:days-since-epoch:seconds-since-day-start
where days-since-epoch is the number of days elapsed since
November 17, 1989. The CD1.1 transmitter scans this file in
order, and stops when it finds a key with an activation time in
the past (relative to the time-stamp of the data being
transmitted.) Thus, to supersede an existing key, you must place
the new entry
before the old one in the file, so that the CD1.1
transmitter will not continue signing subframes with the old
key.
To make the CD1.1 transmitter sign all subframes with a new
key, even when backfilling, you should add the line
key-id:0:0
to the beginning of the file.
9. If you are running it, restart the CD1.1 transmitter with the
command killall -HUP cd11sf. (Using the -HUP option
makes the command send a hangup signal to the CD1.1
transmitter rather than killing it outright.)
10.If you are running it, restart the CNSN transmitter with the
command killall -HUP cnsnauth
50 Issue F