Category: Linux

Categories
Computers Linux

Control Debian daemons

Debian and Ubuntu place startup files for all deamons in /etc/init.d. Symbolic links are then placed in /etc/rc.X to control when deamons are to be started and stopped. While it would certainly be possible to manage it manually, there are a few tools that makes life easier whenever you want to control which daemons are started by default.

Using rcconf

rcconf

Using sysv-rc-conf

sysv-rc-conf

Using update-rc.d

usage: update-rc.d [-n] [-f]  remove
       update-rc.d [-n]  defaults|multiuser [NN | sNN kNN]
       update-rc.d [-n]  start|stop NN runlvl [runlvl] [...] .
		-n: not really
		-f: force

Categories
Computers Linux

Upgrade BIOS on Acer Aspire One

In a previous post I wrote about how easy it was to upgrade the BIOS on Asus Eee Box. It turns out that the Acer Aspire One is just as simple.

  • Go to Acer’s support pages and download the BIOS you want to use.
  • Format a USB stick with FAT32
  • Put the BIOS image file and FLASHIT.EXE (also from Acer) in the root directory. Rename the BIOS image file to ZG5IA32.FD
  • Turn off the computer, then turn it back on while pressing Fn+ESC. Release Fn+ESC after a few seconds. The power button should now be blinking. Press the power button once. This will start the BIOS flashing process.

N.B. Keep the computer connected to AC and do not interrupt the process once it has started. Also, while the above worked very well for me I can offer no guarantees.

Categories
Computers Linux

Unix epoch counter plugin for WordPress

On Friday the Unix time used by many of the computers throughout the world will tick up to 1234567890. As I have learned, most non-techies don’t understand the beauty of this. Strange.

Anyway, I thought I should have a Unix epoch time counter on the web page but was surprised that I couldn’t find a widget to do it. Not to be let down, I realised that this was the perfect opportunity to learn how to write a WordPress plugin.

The result is in the sidebar and the code can be downloaded below. Now all I have to do is wait up on Friday night (0.30 am here in Sweden) and watch the counter step up towards the magic number.

Download epoch-counter.php

Categories
Computers Linux Mac Windows

Extract image metadata

Over the years I have used many small applications to extract metadata from images but none of them were as versatile as Image-ExifTool by Phil Harvey. It support just about any image or video file format your can imaging. And a nice thing is that it is implemented in Perl so that one can easily use it to build a script. And it works cross-platform which is important for me who move between three operating systems on a daily basis.

This is all it takes to extract all metadata from a file:

Categories
Computers Linux

Ubuntu 8.10 – libpolkit error

On a newly installed system with Ubuntu 8.10 you will see these kind of lines in /var/log/syslog:

Nov 24 01:12:31 sirius console-kit-daemon[9837]: CRITICAL: cannot initialize libpolkit

The error will repeat every ten minute or so and the fix to this issue is to install policy-kit, i.e.:

sudo apt-get install policykit

This is described in more detail on Launchpad: https://bugs.launchpad.net/ubuntu/+source/policykit/+bug/275432

Categories
Computers Linux

VirtualBox and Ubuntu 8.04.1

When installing a Ubuntu 8.04.1 virtual guest under VirtualBox 2.06 running on a Mac you will probably be faced with the following error:

Starting up ...
This kernel requires the following features not present on the CPU:
0:6
Unable to boot - please use a kernel appropriate for your CPU.

This problem is due to the fact that the last couple of versions of Ubuntu have been compiled with PAE enabled – but the default guest setting of VirtualBox is that PAE is disabled. So to solve the issue, just stop the virtual guest and enable support in the CPU for PAE/NX, it’s under the advanced general settings. Another solution would be to reinstall the guest using the alternate CD image of Ubuntu (which, last time I checked, didn’t require PAE).

Categories
Computers Linux Mac Photography Windows

Pruning Canon EOS image folders

I have had my Canon EOS 20D since early 2005. The first few weeks I set the camera to save images in JPEG only. After a while I switched over to saving images in both JPEG and RAW and have been doing so up until this year. Up until last year I had been using Windows XP and Windows Vista and having JPEGs around made it easier to look at the photos. However, about a year ago I switched over to Mac and am now using Aperture 2 for my photo cataloging needs. There, the presence of both JPEGs and raw images is nothing but annoying.

Photos with both RAW and JPG files

To avoid the problem with both formats in Aperture I want to import the raw images where available and JPEGs otherwise. But I can’t just remove the JPEG files on a folder level because some images are only available as JPEGs. And with literally tens of thousands of images I just didn’t want to do it manually.

The attached Perl script solves the issue. It takes a source and a target folder as arguments. It then goes through the source directory hierarchy and copies all the image files to the target – but skipping files that are available both as RAW and JPEG. In that case it will pick the RAW file. It uses embedded EXIF tags (the time the photo was taken plus the serial number of the image) to judge if two images are the same. Further, it retains the folder structure but removes certain folders to flatten the target folder structure – I had originally put the RAW files one folder down so that they wouldn’t interfere with the JPEGs when viewing them in Vista’s image viewer.

Please note that I can only vouch that this works on CR2 files and JPEG files from a Canon EOS 20D as that is the only thing I have tested it with. It should be simple to adapt it for other cameras. Also note that the script does not test whether the target folder is empty. You are advised to test the program on some files that you don’t mind losing before you apply it to your entire image library.

I called the script photo_prune, despite the fact that it doesn’t actually prune the source data. To avoid data loss it instead copies the data to a new location.

Download script

Categories
Computers Linux

Create images on the fly from Perl

The image in the previous post was made through a small Perl script and using GD. I had saved a list of files on one of the disks in my DNS-323 NAS and wanted to visualise it. The Perl code for this was this:

Categories
Computers Gadgets Linux

Dlink DNS-323, part 5 – The results

I have written some posts on the issues I have had over the past week with my Dlink DNS-323 NAS. As I wrote yesterday I configured the system to use JBOD to combine the size of the two Samsung 250GB disks and then fill the entire array with data to verify that I would be able to recover the files from one of the disks if the other failed.

The findings are interesting. Please read on.

Once both disks were completely full I powered down the DNS-323 and connected one disk at a time to a computer running Ubuntu 8.04, using a SATA-to-USB adapter.

The leftmost disk showed the following partitions:

Device Start End Blocks ID System
/dev/sdb1 1 66 530113+ 82 Linux swap / Solaris
/dev/sdb2 131 30401 243151807+ 83 Linux
/dev/sdb4 67 130 514080 83 Linux

However, the partition /dev/sdb2 would not be mounted. The error in the log was “VFS: Can’t find an ext2 filesystem on dev sdb2”.

I then switched to the other disk (the one on the right). The partition table looked identical but this time I could actually mount the disk – but whenever I ran ‘ls’ I got a lot of errors saying “cannot access test/D0000220: Input/output error”. The error was caused by files that were on the other disk but were referenced by the file allocation table on this disk. The files that were on this disk were accessible, however.

I then studied what data had been saved on which disk and visualised it. In the image below, each pixel represents two files, each 1MB each in size. The first saved file is the one in the top left and it then goes across and down. Red pixels were saved to the left disk whereas blue pixels were saved on the disk on the right. The original image was 1000 pixels wide, I just shrunk it horizontally to be able to fit within the boundaries of this blog.

The fact that it seems very difficult to recover files on one of the disks means that I will probably stay clear of both JBOD and RAID for my DNS-323. Too bad.

Categories
Computers Gadgets Linux

Dlink DNS-323, part 3 – Fonz fun_plug

This is a continuation of a previous post.

OK, the idea wasn’t exactly brilliant. The script worked fine but completely filling the disks (totally 500GB) from another computer was going to take up towards 40 hours and I am a little impatient. The bottleneck with the DNS-323 is as usual the network connection. So instead, I though about running the script on the DNS-323 itself – which should be very much quicker. But to do that I needed to install a fun_plug to be able to log on and run some software on it.

I had done some small tests with fun_plugs when I first got the DNS-323 but I haven’t checked how much could be done and I was pleasantly surprised. This is a step-by-step description on how to install Fonz fun_plug (FFP) and make it accessible through SSH.

  1. Download fun_plug and fun_plug.tgz from this web site
  2. Copy the files to the Volume_1 folder on the DNS-323
  3. Make sure that the fun_plug file is executable
  4. Restart the DNS-323, then telnet to get shell access
  5. Install all packages as described in the readme for FFP

    6. cd /mnt/HD_a2
    rsync -av inreto.de::dns323/fun-plug/0.5/packages .
    cd packages
    funpkg -i *.tgz

  6. Enable the root password and set a password as well as the shell for root by issuing the following commands

    7. pwconv
    passwd
    usermod -s /ffp/bin/sh root

  7. Verify that you can log on as root

    8. login

  8. If the login worked, then store the password to flash memory by running

    9. store-passwd.sh

  9. Start the ssh server (which will take a while since it has to create keys), then try to log on from another computer

    10. cd /ffp/start
    sh sshd.sh start

  10. If that worked it is time to turn off the telnet server and to enable the ssh server instead

    11. chmod a-x telnetd.sh
    chmod a+x sshd.sh

I am now running the script on the DNS-323 and it is about 7 times quicker than running it via Samba.

More to follow…

css.php