Archiv der Kategorie: Computing | Tech

Eclipse won’t start with: ObjectNotFoundException: Tree element not found

After installing some Mac OS X Yosemite updates today, my smoothly working Eclipse installation on my Mac Book Pro was broken: starting Eclipse failed with „ObjectNotFoundException: Tree element not found“ permanently!

It seems that the only thing that helps is to delete the „.metadata“ directory in the workspace – at least this solved the problem for me. But be aware of the ugly side-effect that a completely new (and clean) workspace will be created …  :-/

Easily work with multiple online identities using Firefox with „ProfileSwitcher“ addon

As many others I have been using Mozilla Firefox in different usage contexts and my online identities are getting more and more … For instance there is a private Google account and one for work, a private Amazon account and one for my company and so on.

Googles Chrome browser recently came up with an identity switch button which addresses the upcoming requirement to work with different online identities in your browser. I missed that in Firefox but I knew that Firefox hat these identities called „profiles“ right from the start.

Today I found the „ProfileSwitcher“ addon which lets you work with different online Identities as different Firefox profiles like a charm. The profiles are 100% separated and you can switch from your private to work profile or similar with a single mouse-click!

Give it a try … it makes your „online life“ much easier …

Howto restore destroyed Evernote LocalNoteStore.sqlite after MacBook crash

Recently, my MacBook Pro running Yosemite crashed while I was downloading data with a USB based GSM/UMTS data modem. Basically this was no problem, the system was restarted and all apps were restored in the state before the system crashed.

… all but ….


Evernote was started but notes were missing and all notebooks were gone – when I clicked on the „Notebooks“ icon, I got the error message that the file:


was corrupt – obviously destroyed when the system crashed. Also trying to sync all notes via my Evernote account from the server did not work.

Happily, I am using time machine — it was a challenge to find the location of the file „LocalNoteStore.sqlite“ because the file cannot be found searching your mac with finder or spotlight (as it is some kind of hidden system file).

After some internet research I was able to quickly restore my local evernote database:

I found my local accout data i.e. the file LocalNoteStore.sqlite and others stored at the path:

/Users/<my_userid>/Library/Application Support/com.evernote.Evernote/accounts/<some_account_id>

I quit the Evernote app.

I started finder, used the „go to folder“ shortcut (Shift+CMD+G) and directed the finder window to the base directory:


Then I navigated into „Application Support“ folder and „com.evernote.Evernote“ and „accounts“ subdirectories using finder (alternatively you can directly „go to folder“ /Users/<your_userid>/Library/Application Support/com.evernote.Evernote/accounts).

Then I selected the acccounts base folder „“, started Time Machine and restored the whole folder with all sub-folders to a Time Machine backup that was about 2 hours old.

After that, I started the Evernote app — everything was working fine again 🙂


live resizing of ext4 root filesystem on linux

Recently one of my virtual Ubuntu servers ran out of disk space. The virtual hardware was extended and some gigs of new disk space were available. The problem was that the machine was not available to me locally, I had only remote access via SSH.

I know I had to resize the partitions to be able to make usage of the newly available disk space – found several entries on the web but all told me that I had to boot into a live disk and use GParted. This meant that I had to drive several hundreds of kilometres to be able to do so ..didn’t really like that option.

After doing some Google „research“ last weekend I found this GLORIOUS blog entry on — it IS possibly to resize the partitions and the ext4 filesystem „live“ even if it is a live system:


Oracle JDK7 on Ubuntu

How to manually install the official Oracle JDK7 including the Mozilla Firefox Java-Plugin on Ubuntu 12.04 LTS (this example is based on JDK7 update 11 with important security fixes – just replace the version to a more recent one):

download most recent JDK version from Oracle website:


extract to /usr/lib/jvm directly:

  • cd /usr/lib/jvm
  • sudo tar xvzf /path/to/download/folder/jdk-7u11-linux-x64.tar.gz

install the new Java installation to the Ubuntu „alternatives“ system:

  • sudo update-alternatives –install „/usr/bin/java“ „java“ „/usr/lib/jvm/jdk1.7.0_11/bin/java“ 1
  • sudo update-alternatives –install „/usr/bin/javac“ „javac“ „/usr/lib/jvm/jdk1.7.0_11/bin/javac“ 1
  • sudo update-alternatives –install „/usr/bin/javaws“ „javaws“ „/usr/lib/jvm/jdk1.7.0_11/bin/javaws“ 1

now configure the alternatives and select the newly available option as default (in the normal case it will be the last option of the list, just check the path to the java installation …)

  • sudo update-alternatives –config java
  • sudo update-alternatives –config javac
  • sudo update-alternatives –config javaws

Install Mozilla Firefox Plugin (for 64bit):

  • mkdir ~/.mozilla/plugins (if not existent yet)
  •  ln -sf /usr/lib/jvm/jdk1.7.0_11/jre/lib/amd64/ ~/.mozilla/plugins/



Complete Erase / Wipe Hard Disk

When I decided to throw my old dual boot Ubuntu + Win XP Laptop away I wanted to really wipe out all data from the hard disk – just for safety these days … I  wondered how it would be possible to do this because I did not find a „low level format“ option in the BIOS of the machine (and I do not trust format-tools based on Windows platform).

The Windows XP partition already was broken somehow, XP didn’t boot any more so
I had to do this from Ubuntu (which BTW also showed lots of disk related errors at boot time, but finally came up and presented the GDM login – yes, it IS SUPREME….)

Erasing and really wiping out the disk from Linux is much easier than I thought, just use the free GNU shred tool:

„sudo shred -vfz -n 10 /dev/sda“
(replace /dev/sda with whatever your disk drive is named)

that’s it — much easier and quicker than dismounting the hard disk out of the laptop and driving over it 20 times with your car 🙂