This note outlines how to configure the computers needed to run DIMMWIT. It is possible to use one of two private network configurations.

Two-computer private network

The original DIMMWIT configuration, consisting of two computers:

• dimmwit: ICE (single-board computer in a box) that runs the Starlight Express CCD camera, to which it is connected by a USB interface.
• dimmwithost: displays the finder application via the X protocol (finder actually runs on dimmwit). Acts as a file server; both the finder software and the DIMM data are stored on dimmwithost.

The two computers are linked by a cross-over ethernet cable (to avoid the need for a hub). This can be a long (50ft) cable to allow remote operation.

Three-computer private network

This more complicated setup allows the observer to analyse DIMMWIT data while other data is being recorded.

The two-computer (laptop and ICE) private network described above is no good for this because mouse events (even motion) are transmitted via the X protocol from the machine displaying finder to the machine running finder, causing dropouts in the data.

One solution that is relatively simple and cheap to implement is to have a three-computer private network, using a switched hub.

The names and roles of these three computers are as follows:

• dimmwit: ICE (single-board computer in a box) that runs the Starlight Express CCD camera, to which it is connected by a USB interface.
• dimmwithost: displays the finder application via the X protocol (finder actually runs on dimmwit). Acts as a file server; both the finder software and the DIMM data are stored on dimmwithost.
• dimmsum (sorry!): Can access data files from dimmwithost, runs the analysis software.

The three computers are each linked to the same switched ethernet hub by a standard non-cross-over ethernet cable. A switched hub is needed to ensure that dimmwit does not see X events due to the observer analysing the data. The cable from dimmwit to the hub can be a long (50ft) one to allow remote operation.

Setting up dimmwit

Under construction.

Setting up dimmwithost

These notes are very brief for now. However, they should be sufficient if you are an experienced Linux sysadmin.

Users

• Create a group 'coast' with GID 103
• Create a user 'coast' with UID 103, default group coast
• Make a directory /home/coast/bin and ensure that its in coast's PATH

Private networking

• Create /etc/sysconfig/network-scripts/ifcfg-eth0:1 (IP 192.168.20.2)
• Put dimmwit (192.168.20.1), dimmwithost (192.168.20.2) and dimmsum (192.168.20.3) in /etc/hosts
• Restart networking

Install software

• Create directories and symlinks:
• mkdir -p /data/oberon/data/finder
• chown coast:coast /data/oberon/data/finder
• mkdir -p /data/oberon/soft
• mkdir -p /net/oberon/data
• ln -sf /data/oberon/data/finder /net/oberon/data/finder
• ln -sf /data/oberon/soft /net/oberon/soft
• Put finder application and CCD drivers (ccd.o, sx_usb.o) from date DD/MM/YY in directories /net/oberon/soft/finder-YYMMDD
• Choose one of these as default: cd /net/oberon/soft; ln -sf finder-YYMMDD/ finder

NFS server

• Ensure required services are started in the default runlevel. On a Redhat machine these are nfs, nfslock and portmap
• Put the following in /etc/exports:

  /data 192.168.20.1(rw) 192.168.20.3(ro)

Ensure that portmap access is enabled in /etc/hosts.allow:

portmap: LOCAL, 10.0.100., 192.168.20.

Make sure that there are no entries in /etc/hosts.deny that would stop NFS working. For the same reason, disable any firewall running on dimmwithost (iptables/ipchains).

Samba server

• If necessary, install Samba (RPMs samba-common and samba)
• Ensure required service(s) (smb on a Redhat machine) are started in the default runlevel
• Edit /etc/samba/smb.conf so that /net/oberon/data/finder can be mounted read-only by any client in 192.168.20. The workgroup should be 'ASMS'

Miscellaneous

• Disable screen saver/DPMS using xset. Put the commands to do this somewhere they will automatically be executed when X is started

ssh key-pairs

• Edit /etc/ssh/ssh_config:

  ForwardX11 yes
  CheckHostIP no
  StrictHostKeyChecking no
  Protocol 2,1
  

• As user coast, do ssh-keygen -t rsa, entering a blank passphrase
• Connect both dimmwit and dimmwithost to the private network
• Make dimmwit's disk writable: ssh root@dimmwit rw
• Copy the public key to dimmwit, to enable login without a password as both coast and root:

  scp /home/coast/.ssh/id_rsa.pub coast@dimmwit:.ssh/authorized_keys2
  scp /home/coast/.ssh/id_rsa.pub root@dimmwit:.ssh/authorized_keys2
  

Tests

With both dimmwit and dimmwithost connected to the private network, and the CCD camera connected and powered up:

• Log into dimmwithost as coast. Check that you can ping dimmwit
• On dimmwithost, run 'initccd' then 'finder'
• Check that you can save data from finder
• Connect dimmsum to the private network, check that dimmsum can mount dimmwithost's disk and that you can read the data
• In place of dimmsum, connect Dan's laptop to the private network (it should be configured as 192.168.20.something), and check that it can access the data on dimmwithost

Setting up dimmsum

Under construction.