It’s super easy, to know if a file is sparse or not. Just use the ’s’ option of ls.

ls -alsh

will yield:

4.0K drwxr-xr-x 9 root root 4.0K 2010-03-23 18:22 .
4.0K drwxr-xr-x 23 root root 4.0K 2009-01-09 19:47 ..
12G -rw-r----- 1 root root 24G 2007-01-10 19:55 dompat.data
3.7G -rw-r--r-- 1 root root 7.1G 2009-01-06 21:09 dompat-hardy.sys
501M -rw-r----- 1 root root 501M 2007-01-07 16:40 dompat.swap


Where the first size column is the effective space taken on disk while the second size column is the max space of that file. We see that dompat.data is sparse, since its max size is 24 GB while it takes only 12 GB on disk.

References

• More information on command which can handle sparse files in this article

GPGMail for OS X 10.6.2

Just put it inside ~/Library/Mail/Bundles and restart Mail. (More information on GPGMail’s web page.)

Edit: This is not an official version of GPGMail. There is still no official version of GPGMail compatible with Snow Leopard.

Unfortunately I had to redo the NFS config after upgrading and I noticed that Directory Utility was not present anymore in Snow Leopard.

Here is what I found out after some research:

Remote NFS URL: nfs://[server]/[path]
Mount location: [path to local mount folder]
Advanced Mount Parameters: -i,-s,-w=32768,-r=32768

sudo automount -vc

That’s it. The NFS share should now be accessible.

References:

Although you can resize a live partition with Disk Utility (great feature, even if you booted with it), you cannot move the base position of a partition. You can merely resize it, if more space is available. So I had to back my second partition up for later restoring it. I went for Time Machine, since I was already using it for backing up my laptop.

Time Machine Caveats

Unfortunetely I noticed a couple of caveats during the restore operation:

Solution for merging two partitions

I finally found a solution to restore the second partition or to merge them: I had to fiddle directly with the Time Machine backup, copying manually the files I wanted from the second partition to the first, and did a restore of the first partition using Time Machine restore utility.

Here are the details of the steps I took:

This worked for me. You should now have a merged partition on your drive, the restore utility having removed the ACLs during the operation. Phew! This was not a straight forward action! I still cannot believe that Apple did not take into account that people can have more than 1 partition on their drive (I might still have missed the way to do it, did not find it so far though).

Links/Info

alias screen='TERM=screen screen'

Install Perl. On Windows (yeah, I know. It’s at work. ), install Active Perl version 5.8.8.X. Don’t take the last one, the 5.10.0, as Pidgin does not support it yet.

It’s easy to fix that. Using the web interface, go to the ‘Administration’ > ‘Buttons / LED’ page. Replace the custom script by the following code:


# status: 1: wifi on, 0: wifi off
status=$(wl -a eth1 dump | grep associated | cut -d " " -f 2);
# toggle wifi & amber led
wl -a eth1 $([ $status -eq 0 ] && echo up || echo down)
led amber $([ $status -eq 0 ] && echo on || echo off)


Then change the setting for ‘0 – 2 Seconds’ to ‘Run Custom Script’. That’s it. Now when we press the button, the wireless is toggled and the LED switches itself accordingly.

Tested with Tomato 1.19.

Of course, one of the most energy hungry device I have is the server, which is always switched on. I was expecting a consumption of about 60 W, because I tried to choose efficient components, some of which were listed on a review regarding a green computer consuming 54 W when idle. My hardware configuration is the following:

• Processor AMD 64 x2 EE 3800+, dual core and energy efficient version (which is actually quite cheap)
• Micro-ATX Mainboard M2NPV-VM with AM2 socket
• 2 GB of RAM (DDR2 PC4300)
• 2 Seagate 7200.8 250 GB hard disks used as a software RAID-1 array
• Power supply ElanVital 500W, ATX, with 80% efficiency.
• Plextor Plexwriter DVD burner

So I shut downed my server, plugged it in the measurement device and booted it. The value I could read on the device, after the reboot was finished and the server was idle, was higher than expected: 85 W. I was not very happy with that value and began to try to optimize it.

• I first tried to remove the DVD burner, but I got just 2 W of reduction, which was not good enough.
• Then yesterday I tried to install the last stable release of Ubuntu, which is Ubuntu 7.10 gutsy 32 bits version (I add previously Ubuntu feisty with a XEN enabled kernel). I was pleased to see that the server was only consuming about 68 W (DVD burner included). I then tried to re-install XEN and after rebooting saw that I was again at 85 W. So the XEN kernel had different options enabled that were not optimized for a good power management.
• I got back to the stock kernel and tried to activate the automatic spin-down of the hard disks. I did this using the command

  hdparm -S 60 /dev/sda
  hdparm -S 60 /dev/sdb

  which spins down the two disks after being idle for 5 minutes. I was able to grab a few watts and get down to 60 W, which is not too bad. I added the two commands in /etc/rc.local so that it gets executed automatically on boot.

• I then tried to activate the automatic CPU frequency scaling, so that when the processor has a low usage, its frequency gets automatically reduced, hence saving some energy as well. I was getting some problems using the module powernow-k8, so I updated the bios to the latest version (1201), which resolved that issue. I could then install correctly the cpu scaling daemon. I just had to run

  apt-get install cpufreqd

  and then edit the file /etc/default/cpufreqd and insert “powernow-k8″ in the option CPUFREQ_CPU_MODULE (you can check which module you need to use here). With these two operations, the BIOS upgrade and the cpu frequency scaling, I was able to grab a few watts, getting down, when the server is idle, to about 53 W, which is already a lot better than the 85 W I was getting without tuning.

The options I might consider now are the following:

• I could reduce significantly the power consumption if I automatically switch off the server every night. I am using it also to do a distant backup of another computer, but I could setup the BIOS to switch it on every night to do that, if it is not already the case. The only thing I would need to do is just to switch the server on, whenever I want to print something or hear mp3’s, which is not too bad. The server would then switch itself off at night, after doing the backup.
• If I want to use XEN, I should compile my own patched kernel (for XEN) and tune the power management options to get the same consumption as on the stock kernel.
• I could try to tune further the kernel options, which I am not sure that I am going to do, as it is much more convenient to use the stock kernel than to use a self compiled one (e.g. for updates).
• I could try to find a way to cut off the consumption of some other electrical devices, which are most of the time not used or in standby mode, but do consume power anyway. Like for instance the laser printer (standby 14 W), the external backup hard disk Seagate 500 GB 7200.10 (standby 12 W), the wireless access point WRT54GL (always on, 14 W) or the cable modem (always on, 12 W). Not sure how I can do that. Of course I could plug some of these devices in a multi socket with a switch, but I would need to turn it on each time I want to access the internet using my laptop and turn it off afterwards (in addition it’s not compatible with my automatic distant backup). Not very elegant. I guess I will have to think about that issue.

Additional links:

• How to reduce power consumption Nice howto based on Linux with other options presented.
• Ubuntu forum post Use cpufreqd to tune CPU frequency
• Ubuntu forum post Which module to use for cpufreqd

PAP2 Configuration for Voipbuster