After visiting one of our datacenters and chatting with local siteops, it occurred to me that it would be rather useful to have cables that can be traced visually from any point along the cable. So consider a cable (network cable, power cable, whatever) that is made of material that can change color or emit light based on touch. That is, you grab the cable and it lights up from end to end.

If you want to get fancy, make it run blinking light rings from one end to the other (or from the point of contact to both ends), to allow you to follow it. Or let it have running LED text ("switch-A-port-N <-> host-N-rack-A") along the length of the cable etc.

If such a think already exists, oh well. If not, remember you heard it here first!

1/2 pound sirloin beef, sliced in strips
one garlic clove, minced
4 chives, thinly chopped
1 tomatoe, cut in chunks
4-5 basil leaves, chopped

some soy sauce
some fish sauce
some sesame oil
a teaspoon of green curry

Marinate beef strips with garlic and chives in soy sauce, sesame oil and green curry. Take strips out of marinade and stir fry until cooked through. Add tomatoes and reduce heat. Cook for two minutes or so. Add fish sauce and some more soy sauce to remaining marinade, mix and add to pan. Serve with rice and sprinkle with basil leaves.

Served with cucumber salad: half a cucumber, sliced thinly. Squeeze half a lemon, mix with sunflower oil, pepper and sault and a teaspoon of mayonnaise.

Suppose you have a set of hosts S that you can only reach via ssh from host V
by authenticating against a RADIUS server R and tunnelling your connections
through a proxy server P from R.

So you set up an ssh config with the appropriate tunnels on V and everything
is well. When you're on V, you can reach any host in S via ssh.

Now suppose that host R can only be reached from V, but not from your local
host L. So what you want is an ssh configuration that allows you to tunnel
every connection to a host in S through V to R (and thus from there through P
to the final host).

The configuration below allows you to do just that:

On V, add to your ~/.ssh/config:

Host proxy_from_v
        HostName R
        LocalForward 9342 P:22              

Host *.S
        ProxyCommand /usr/bin/ssh -p 9342 localhost /usr/local/bin/nc %h %p

On L, add the following to your ~/.ssh/config:

Host proxy_to_v
        HostName V
        LocalForward 9922 localhost:9342

Host *.S
        ProxyCommand /usr/bin/ssh -p 9922 localhost /usr/local/bin/nc %h %p

Then, to setup the ssh tunnel, run:

ssh -t proxy_to_v "ssh -t proxy_from_v"

This gets you to V and from there sets up the proxy through R to P.

Having sorted this out without a whiteboard makes me feel like after having a
Pangalactic Gargleblaster. You may draw yourself the corresponding picture
with clouds representing the interweb and pipes with numbers on them the
tunnels. Don't forget to get the arrows right! :-)

A presentation on Shell Coding given at SCALE 2007: Useless Use of *.

netmeister.org is now brought to you by NetBSD/macppc.

It's running on a Mac Mini, using this kernel config file (this actual kernel). Installation was done using these instructions -- whoever wrote them clearly was a genius.