OpenSSH 5.4: Great Scott!

One point twenty one jiggawatts! Yesterday (March 8, 2010) the OpenSSH project released version 5.4 and naturally will start hitting the various distributions and platforms soon, and again there are some great things to be interested in:

  • Although many distributions of OpenSSH have SSH1 disabled, the project is now shipping with SSH1 disabled by default.
  • There is the ability to revoke keys (host and user) in both sshd and ssh.
  • Netcat mode connects stdio on the client to a single port forward on the server. For example the following would connect to smtp.server.example.org on port 25, and redirect the output to stdio on my client side. Useful if you need to test connectivity to a mail server, but can't from your direct location, but can from your SSH server (my.ssh.server.example.org). ssh -W smtp.server.example.org:25 my.ssh.server.example.org That has pretty much bags of possibilities, ranging from simple connection tests to piping a file to a remote server that you can't get to directly.
  • sftp-server has gained a read only mode!
  • Passphrase-protected SSH2 private keys are now protected with AES-128 instead of 3DES. This counts if you reencrypt your key or create a new one.

Graphing Micromiser with Munin

I've been playing with Micromiser for a few days, and wanted to graph what it claims to be saving on one of the servers. Luckily this is pretty easy with Munin (which is already running on the box), since Micromiser logs into syslog occasionally. Below is the plugin I hacked together that looks at syslog and uses sed to extract the percentage saving. It's not pretty, but it does work.

Perhaps this'll save you a few minutes.

#!/bin/sh

# Plugin to graph the savings made by micromiser

if [ "$1" = "autoconf" ]; then
        echo yes
        exit 0
fi

if [ "$1" = "config" ]; then

        echo 'graph_title Micromiser Savings (percentage)'
        echo 'graph_args --upper-limit 100 -l 0'
        echo 'graph_vlabel savings'
        echo 'graph_category system'
        echo 'savings.label savings'
	echo 'savings.draw AREA'
        echo 'savings.min 0'
        exit 0
fi

RES=`grep Estimated /var/log/syslog | tail -1 | sed 's/.*(\([0-9\.]*\)%)$/\1/'`
echo -n "savings.value $RES"

Ubuntu Server 10.4 (Lucid Lynx) and Hyper-V

If you've noticed that the next Ubuntu Server version (10.4, Lucid Lynx) has the Hyper-V kernel modules packaged, alebit in drivers/staging, I'd suggest not dist-upgrade'ing even your development servers for the moment. The reason is simply that you need to devote time to ensuring that the kernel modules will continue to work with each kernel version - right now you can't seem to rely on the modules actually loading successfully from the corresponding /lib/modules/2.6.*/kernel/drivers/staging/hv directory. Which isn't a problem, provided that you have the time to deal with it.

The long and short of it is that if you're currently looking to use any flavour of Linux under Hyper-V the "old" rules still apply;

  • Use the legacy network adapter
  • Set static MAC addresses under the VM settings (unless you want to faff with udev)
  • and learn to live with the performance penalty

So long KarmaSphere

After quite some time serving the world, KarmaSphere's reputation lists are ending. If you're running KarmaSphere on your mail server(s), now would be the time to start thinking about removing that as an anti-spam feature.

To the KarmaSphere team, I wish you well with your new endeavors, and I hope that you continue to come up with innovative products!

RemasterSys is awesome!

In that past I've created custom live unix distro CDs for myself and although it worked I found that it was so time consuming and generally such a pain in the bum that it just wasn't worth it. Yesterday I had the need (that nerd need, not because I had to, but because I wanted to) to create a customised CD for the house1. I'd heard good things about RemasterSys and figured now was the time to try it.

Holy crap it's awesome. Customise your setup as you want it, make sure you do the necessary system wide alterations (/etc/skel, and so on) and then just fire and forget. A few minutes later you either have an ISO or the CDFS ready to be altered before you turn it into an ISO. I didn't have to worry about clearing down rubbish, then mashing it all into squashfs. It Just Worked.

If you need to create a custom Debian based live CD quickly, then I encourage you to look at RemasterSys. It's quick and works like a dream.

[1] We have an old laptop with a mostly dead hard disk, and it's been running an Ubuntu live CD for months. Sadly it means that everytime you shut it down certain things need to be reinstalled, such as Flash support. No longer is this an issue thanks to Redcatch Linux Five Thousand.

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