f.lux takes the pain out of screen reading


Warm and easy on the eyes at night, bright enough to show “true” colours in daylight.

More generally, avoid pure blues in your screens and LEDs. Pure blues are more difficult to focus on than warm reds and yellows, and if you try to focus on reds and blues at the same time… you’ll never do it. Physics says so.

Simplified guide to DNS, SOA




Make sure your SOA points to your correct DNS server via nslookup to the two name servers you think may be problematic.

Check the serial number entries (yyyymmddrr) – the largest serial number should also be on the SOA server.

If the highest serial number is on a non-authoritative server, check *that* server’s SOA, correct it.

Then temporarily:

  • set the faulty server’s serial number to something lower than that of the genuine SOA server.
  • Lower the faulty server’s Refresh interval to e.g. 600 seconds.

Wait for 10 minutes and make sure the zone on the faulty server matches the zone on the SOA server – especially the serial number.

Raise the now-fixed server’s Refresh interval back to e.g. 86400 seconds.



Under active development by Don Brady who spearheaded the transition to the current Mac file system, hfs+ 20 years ago now; get ZFS for OSX from ZEVO.

ZFS is for anyone who cares about silent disk corruption; the stuff that’ll kill your data long before any mainstream operating system warns you of your hard disks’ impending death.

If you use OSX for anything more than web browsing and light office work, consider it seriously… The community edition is free at the moment, very stable and easy to use if you can handle a little command line work with Terminal.

Virtio paravirtualised NIC drivers for Server 2008 / Win 7 on virtualbox

On your Virtualbox host; download the ISO of generic windows paravirtualised drivers from here:


Shut down your Windows VM and set your its Adapter Type to “virtio-net”.

Boot the Windows Vm and mount the downloaded driver ISO as a virtual CD drive.

Log on to the VM and check you can browse to the virtual CD’s \Win 7\[x86|amd64]\ folder; use devmgmt.msc to install the new drivers on the paravirtualised NIC hardware (“Trust software from Redhat”).

You shouldn’t need to to reboot.


OSX NFS Storage Repository for XenServer

Setting up an iso Storage Repository for my XenServer testbed. CIFS is an option, but after a couple of “SR_BACKEND_FAILURE_222Could not mount the directory specified in Device Configuration” errors, I decided to try NFS, telling myself that CIFS/SMB is an ugly way of connecting unix systems to each other anyway…

OSX supports NFS nicely, and there’s a good nagware GUI available from Breslink.com.

Five minutes later my CIFS share was available over NFS.

I caught the same “SR_BACKEND_FAILURE_222…” connecting from XenServer to the NFS share until I specified “Allow mounting the folder and any subfolders inside” in the share’s advanced options – which may well be where the CIFS sharing attempt failed. XenServer presumably tries to read every subfolder of a Storage Repository as it’s mounted. I’ll test later.

Incidentally, the minimum required security was “System Standard Only”. The only other non-default sharing option was limiting access rights to the local class C subnet.


Planning a Citrix / XenServer installation

http://project.citrix.com/ – a hosted project planning service better than any HOWTO I’ve come across yet.

It’ll be interesting to see how well it works for a small test-bed installation.

More details (if you want a more traditional, indexed approach):




Routing problem(?) between BeThere and Talktalk

I’m trying to ssh to an OpenSSHD-equipped host at {redacted}.{dynservice}.org (a TalkTalk consumer adsl account) from an nix laptop on a BeThere ADSL network.

I have no problem using ssh to connect to other servers on the internet from BeThere. *But* when I disconnect my laptop from the landline Wi-Fi and tether it through a Vodafone android phone, the laptop can ssh into the host at {redacted}.{dynservice}.org perfectly. The time-out problem only seems to arise when I’m trying to ssh from my BeThere ADSL account.

Truth table:

  • Vodafone to Bethere = ssh OK
  • Vodafone to BT = ssh OK
  • Bethere to BT = ssh FAIL

When I traceroute between the hosts, there seems to some kind of routing loop (repeated patterns of IP addresses in the traceroute).


As of this morning, the ssh-gap (and the apparent routing loop) had cleared up. Still haven’t had a definitive answer from BeThere, but I”m happy that someone, somewhere has fixed something.

Dual boot OSX and Xen Server

Based (hopefully very closely) on an existing HOWTO.

I have an excellent general purpose i7 machine that usually works as a Hackintosh; for the sake of desk space I want it to function as a Citrix VDI testbed.

Update: As osx86 doesn’t like VT-d and Citrix definitely does, I’m using BIOS profiles with separate boot device orders.