The following signatures couldn’t be verified because the public key is not available

GPGUbuntu is nice to use, it works flawlessly on most systems. Especially the packet management is awesome and therefore I wanna say thanks to Debians developers for that.

What so ever, sometimes you have to add a Repository to the sources.list which creats a failure during fetching the package data. The failure most of the time is based on a not verified public key.
To get rid of that there are a few steps to do:

  • GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 28A8205077558DD0
  • sudo gpg –keyserver x-hkp://pool.sks-keyservers.net –recv-keys 28A8205077558DD0
  • sudo gpg –export –armor 28A8205077558DD0 | sudo apt-key add –

Be aware that you should only add keys if you really trust the repository.

Update
A shorter version to add keys of a repository using one command:

sudo apt-key adv –recv-keys –keyserver keyserver.ubuntu.com 28A8205077558DD0

Add extra storage on the fly with LVM2

How to add extra storage on the fly using LVM.
Here are the steps I used to get my 80GB Maxtor(sda) and 60GB Western Digital(sdb) to work together as one logical unit. I am also using ext3 as my filesystem because it supports on-line resizing.

  • Fresh install of Ubuntu Server 8.10
  • Run updates:
    sudo aptitude update && sudo aptitude safe-upgrade
  • Reboot because of kernel upgrade
  • Figure out what the extra hard drive is (mine is sdb):
    sudo fdisk -l
  • Partition the hard drive as Linux LVM:
    sudo fdisk /dev/sdb
  • Initialize partition for use by LVM (on my system sdb1 is swap):
    sudo pvcreate /dev/sdb2
  • Display attributes of volume groups to find your group name (mine is ubuntu-server):
    sudo vgdisplay
  • Add my physical volume to my volume group:
    sudo vgextend ubuntu-server /dev/sdb2
  • Now extend the logical volume root to include the new physical volume:
    sudo lvextend -L128G /dev/ubuntu-server/root
  • Lastly, resize the filesystem to include the new free space:
    sudo resize2fs /dev/ubuntu-server/root

Original article posted by Useful Ubuntu

Installing Ubuntu on a PowerMac

After a lot of testing and playin around with my PowerMac (which I do not own any more) I found out that Ubuntu 10.10 is working without any problems out of the box. That was the best solution for first time installation and then I upgraded to the newest version.

But before I came to this conclusion I collected a few helpful links which I want to share

PPC – Yaboot – How to configure the PPC Bootloader – Multibooting

Install Gnome3 on Ubuntu 11.04

Unity is not everybodies business – to get Gnome3 and all its benefits follow these simple steps and choose it afterward from your login screen as your loing desktop.

Open the terminal and run the following commands

sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install gnome-shell

via UbuntuGeek

Upgrading to a newer Version of Ubuntu

Based on the fact, that Ubuntu 9.04 was announced today, it is a good idea to explain how to upgrade every Ubuntu Version using the command line.

  1. sudo apt-get install update-manager-core
  2. verify /etc/update-manager/release-upgrades
    to use LTS or Normal based on your preferences
  3. sudo do-release-upgrade

After that, follow the messages on the screen to upgrade your system to the newest Ubuntu Version.

Cacti: Passwords do not match, please retype.

With the message “Error: Passwords do not match, please retype.” Cacti tried to make my life horrible today, but not with me.

If you are running Cacti 0.8.7b (which is the standard version located in the Ubuntu repositories) you will be prompted with this error after editing a host using Firefox 3. The error is based on an auto complete bug within the form. There are two solutions to avoid the problem (which worked for me):

  1. Before saving all the settings you have to delete (if not in use) the value in the password field of the SNMPv3 settings and than switch back to your preferred method of fetching information.
  2. Apply the patch which was provided by RichardBronosky in the Cacti Forum solving the problem.
  3. The easiest way to apply this patch is to cd to your cacti directory and:
    1. THIS IS IMPORTANT. Verify the validity of the URI like this:

    Code:
    curl -L http://forums.cacti.net/download.php?id=14681

    2. If it looks like a safe patch, then apply it directly from that URI via curl:

    Code:
    curl -L http://forums.cacti.net/download.php?id=14681|patch -p1 -N

Auto-Logout in der Bash Shell

Eingelogged ist man oft schneller als ausgelogged. Sehr problematisch ist es, wenn eine Root-Shell nach dem Verlassen des Computers offen bleibt und jeder Anwesende hier herumwerken kann. Aus diesem Grund gibt es innerhalb der Bash Shell die Environment Variable TMOUT, setzt man diese, entweder per Hand mit “export TMOUT=120” oder innerhalb der .bashrc oder /etc/profile, wird ein automatisches Logout nach der angegebenen IDLE Time durchgeführt.

Ich hab folgendes in meiner /etc/profile stehen:

IDLELOGOUT=120
echo “Automatischer Logout nach $IDLELOGOUT sekunden!”
export TMOUT=$IDLELOGOUT

Damit werden alle User automatisch nach der bestimmten Inaktivität ausgelogged. Bitte nicht vergessen, wer als User eingelogged ist und mittels “sudo su” die Root-Recht erlangt hat wird nicht automatisch ausgelogged. Um dieses Problem zu lösen muss ich noch etwas nachforschen.