Category: Shell

How to fix “There is no public key available for the following key IDs”

When I run the command

sudo apt-get update

I got this warning:

There is no public key available for the following key IDs: [key_id]

To fix:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [key_id]

The command above downloads the missing key using the hexadecimal numbers given the [key_id] with apt-key. After running apt-key to download the missing [key_id], any packages from that repositories will be considered trusted.

How to find out the actual screen resolution from a shell script

When I have to personalize the settings of my FreeNX client, I have to know which resolution should I set in order to get a maximized window which perfectly fit my desktop. Once I get connected to my remote desktop and having its window resized, I get the new resolution with:

xdpyinfo  | grep dimensions
dimensions:    3200x1200 pixels (847x318 millimeters)

or

xrandr -q | grep current
Screen 0: minimum 8 x 8, current 3200 x 1200, maximum 8192 x 8192

Skype: fix “Fatal: QWidget: Must construct a QApplication before a QPaintDevice Aborted (core dumped)” or “Segmentation fault (core dumped)”

If you are running Prelink on your Gnu/Linux distribution you could get a crash when launching Skype. To inspect the real error just launch Skype using the CLI, you might get:

Fatal: QWidget: Must construct a QApplication before a QPaintDevice
Aborted (core dumped)

or

Segmentation fault (core dumped)

It has taken me several days before realise that there was a issues with Prelink. To fix it you simply have to blacklist Skype in the Prelink configuration file.

Remove Skype

sudo apt-get purge --remove skype-bin*
sudo nano /etc/prelink.conf

Add the line

-b /usr/bin/skype

Reinstall skype

sudo apt-get install skype

Rebuild the shared libraries cache

sudo ldconfig

Tested on Xubuntu 12.04. More info on this issue here:

https://bugs.launchpad.net/ubuntu/+source/skype/+bug/1002187

Increase your Virtualbox VDI size

With the latest version of Virtualbox, at this time 4.2.0, it is possible to easily modify the VDI file size with just one command.

For instance, I had to increment up to 30Gb my virtual machine with which I test Mint Mate edition:

vboxmanage modifyhd --resize 30000 linux_mint_13_x64_mate.vdi

Then you have to use a partition editor, such as Gparted or PartedMagic, to expand or move your partitions.

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