the birdhouse in my soul

Sudoku's have been quite a hype in recent years, attracting puzzle lovers all over the world. I have solved quite a number of them myself, or at least, that's what I thought until earlier this year. Seeing the daily "difficult"/"superieur"-level sudoku in a Swiss free newspaper, a coin dropped. They've been publishing the same sudoku for over a year now. Yes, that's right, the same sudoku, every day. Or more precisely, an equivalent sudoku. By using four simple transformations, yesterday's sudoku can be transformed into today's, and so can the solution ! rearranging rows withing the same 3-row block (idem with columns) rearranging the order of the 3-row blocks (idem with 3-column blocks) permutating 123456789 into a different order transposing the grid (making rows into columns and vice versa) How long can they keep this up, you wonder ? There's a total of about 1.2x10E12 combinations to every sudoku puzzle. It will take them 4.6 billion ...

An interesting issue popped up: how can a program or script in a VM determine the type and version of the hypervisor it is running on ? This is important if you want to install version-specific software, like the VMware Tools ("enlightened hardware drivers", as MS would say). Knowing that you're running in a virtual machine is pretty easy: you can look at the hardware, on VMware you'll see "00:0f.0 VGA compatible controller: VMware Inc Abstract SVGA II Adapter" which makes it pretty clear, and lspci -v says "Subsystem: VMware Inc" for every PCI device. Easy as 1 2 3. But which version of VMware ESX is it ? Not that easy, it seems. But we (hi Dag !) found a unique signature for each ESX version: looking at dmidecode, the output in the "BIOS Information" section lists a Release Date and an Address field. These seem to be unique for each ESX version. The mapping we could build was: ESX 2.5 - BIOS Release Date: 04/21/2004 - Address 0xE8480 -...

Lots of people seem to experience freezes of Nokia Sports Tracker on their E71 smartphone. Google easily finds articles suggesting a workaround: "don't leave Nokia Sports Tracker in the foreground". However, that doesn't help. What does help, is setting the access point to "None" in the Nokia Sports Tracker settings. The program doesn't like an inaccessible access point in its preferences.

When I set up my test environment earlier this year, I put two Samsung HD103UJ 1TB drives in the main file server, and configured them as a RAID-1 software mirror through mdadm. Just months later, smartd was spewing out messages about both drives: Device: /dev/sda, 8 Currently unreadable (pending) sectors . That got me very worried... I replaced one of the drives with a WDC WD1000FYPS-01ZKB0, and rebuilt the mirror. Actually, I built new mdadm mirrors from smaller partitions to lessen the risk of a two-drive badblock scenario. Regardless, my data got moved, so now everything gets stored on two different drives. Different makes, manufacturers, models. Same size though. The problem is, I can't RMA the drive. It's still in warranty, but when running badblocks -w on the drive, it shows no problems whatsoever. Moreover, the SMART status has gone back to: Current_Pending_Sector 0. So not only is the problem undetectable by badblocks, it even makes it go away in the SMART counters wh...

Most Linux system-administrators are well aware of the benefits of LVM. With online resizing of filesystems and migration of data from one disk to another, it's fantastic. But don't assume that your system will do everything for you. If your system has one disk, that you used as a physical volume (PV) in a volume group (VG), where your root partition is stored as a logical volume (LV), you can easily add a new disk. Add the disk physically, boot up, use pvcreate and vgextend to include the new disk in the existing volume group. Just don't reboot, at least, not yet ! Your system requires a manual rebuild of its initial ram disk /sbin/mkinitrd -f /boot/initrd-2.6.18-92.1.10.el5.img 2.6.18-92.1.10.el5 If you forget to do this, your system will not boot, because it won't find all the components necessary to activate the VG it needs to access the root filesystem. Symptoms: kernel loads, initrd loads, root filesystem can't be mounted because the volume group doesn't e...

One of the first steps in a virtualization project is building a list of workloads that will get virtualized, with a measurement or estimate of the resources that they will need. X MHz and Y MB, sum everything up, and let's say you get 30 GHz of CPU power and 20 GB of RAM. The hardware you'd like to run all those virtual machines on can handle two CPUs (dual-socket), four cores each (quad-core). That means that every physical server will give you between 20 and 25 GHz of CPU power. For memory, you'll buy 12 GB of RAM in each server. So the plan is to buy two of those servers, right ? Well, as long as your infrastructure is 100% healthy and running OK, two servers will do the job just fine. You've got enough resources, with a bit of headroom for overhead and future growth. But what happens when one of the physical servers is down ? Think of hardware problems, think of virtualization software upgrades, think of patching the hypervisor. Then the available resources are dow...

Are you still using Red Hat Enterprise Linux 2.1, or CentOS 2.1 ? Then this news is of great importance to you: planned End-Of-Life for these products is approaching ! After May 2009, there will be no more security updates for RHEL 2.1, nor support from Red Hat. It's not really news , as the lifecycle of RHEL products has always been clearly announced and published . If you missed all that, this is the time to start planning an upgrade. Your Red Hat subscription gives you the right to use the newer versions of RHEL, so upgrading is all you need to do. Need help planning an upgrade to RHEL 3, 4 or 5 ? I can recommend some experienced consultants ! ;-)