Background

Control of the DEIMOS rotator is managed by roto, a Linux server mounted in Bay B of the DEIMOS cradle. The machine is diskless and boots from a partition on keamano. In case of failure, a space computer exists and can be installed in place of roto, as described below.

Procedure

To replace the rotation control computer, do the following:

Disconnect the original computer.
Connect the spare. This includes:
- Galil 100-ping high-density main cable;
- Galil supplementary DB-25 cable;
- keyboard and monitor cables (used for testing / monitoring only; not actually needed at runtime);
- RJ-45 network connectors (connect the PCI network card (upper jack) to the private net; if also using a public net, connect the on-board network interface (lower RJ-45 jack) to the public net);
- power cord.
Do not turn on the computer yet.
Have a systems administrator reconfigure the dhcp server (note that this requires root access):
- Edit /etc/dhcpd.conf, and replace the MAC address of the rotation computer with that of the spare.
- Restart dhcpd, so that it re-reads the config file:
```
		/etc/init.d/dhcp stop
		/etc/init.d/dhcp start
		/etc/init.d/dhcp status
```
Turn on the replacement computer.

Additional information

Here is an extract from keamano's /etc/dhcpd.conf:


    34  #               hardware ethernet       00:01:02:C6:f0:84;  ROTO (faster cpu)
    35  #               hardware ethernet       00:01:02:69:56:87;  SOTO (spare)
    36  
    37  group {
    38          use-host-decl-names     on;
    39          option log-servers      keamanop.keck.hawaii.edu;
    40  
    41          host rotop.keck.hawaii.edu {
    42                  hardware ethernet       00:01:02:C6:f0:84;
    43  #               hardware ethernet       00:01:02:69:56:87;
    44                  fixed-address           192.168.6.6;
    45                  filename                "/tftpboot/lts/vmlinuz.3c905";
    46          }
    47  
    48  #       host sotop.keck.hawaii.edu {
    49  #               hardware ethernet       00:01:02:69:56:87;
    50  #               fixed-address           192.168.6.7;
    51  #               filename                "/tftpboot/lts/vmlinuz.3c905";
    52  #       }
    53  
    54          host lapthing.keck.hawaii.edu {
    55                  hardware ethernet       00:01:03:C7:FF:2B;
    56                  fixed-address           192.168.6.101;
    57          }
    58  }

Note lines 42 and 43. To exchange computer identities, comment-out line 42; uncomment line 43, and restart the dhcp server.