Ubuntu Tutorials

I’ve been teaching software RAID on RHEL5 for some time now and today I came to the realization that nearly every student I’ve ever taught that is currently using RAID is using hardware RAID.  Nobody seems to use software RAID, at least in what I’ve run into.

Now, in my mind, the performance difference between the two (software vs hardware) can come down to how much you’re willing to spend on your hardware RAID controller.  A quick example:

Lets say you put a cheap hardware RAID controller in your quad-core machine, which normally has a minimal load.  I would think the quad-core machine would have more than enough processing power to handle the RAID, as compared to the cheap hardware controller.

On the flip-side, if you get a quality card that has RAID specific instruction sets it could likely perform even better than a quad-core machine.

Is this an accurate assumption?  I should mention that I have only really used software RAID so I don’t have a lot of first-hand experience on the other end.  What I’m looking for is your experience..

I’d really like to hear the communities thoughts and experiences on hardware RAID vs software RAID.  Which do you use and why? (The why is what I’m looking for).

I just added a WordPress plugin polling system and I’d really like to hear from all of you regarding what you’d like to see more of at Ubuntu Tutorials.  I know there are thousands of you that read the blog, but I only hear from a select few by way of the comments section.

Please take a minute and come visit the poll located on the right sidebar of the blog beneath the RSS icon.  I’d love to write content more targeted to the readerbase, and I can’t do that unless you tell me what you’d like to hear!

Thank You,

Christer

I ran into some Mozilla Firefox easter eggs this afternoon.  Do you have any more that I don’t know about?

Visit these addresses in Firefox 3:

about:mozilla
about:robots

Also some other interesting things to find:

about:config
about:cache
about:credits
about:license
about:buildconfig

(Reference to the “warranty” is a warning message and I’m sure its a joke.  Refer here to previous warning messages prior to this one.)

I covered VNC this afternoon in my Linux system administration course and the question came up on how to secure VNC. You may or may not be aware than VNC is not encrypted by default, which could be a security concern.

If you use VNC regularly to connect to other Linux machines you may want to consider adding a level of encryption with SSH. Here is a quick run-down on how that is done:

If you look at the man page for vncviewer (man vncviewer) you’ll notice there is a small section for -via. The -via option, as outlined in the man page will do:

Makes the connection go through SSH to a gateway host. The gateway should be the target host for best connection secrecy.

Basically this is saying that you can tunnel VNC over SSH within your connection command. Let’s give it a try.

vncviewer -via user@host localhost:0

This, of course, will require that you have both ssh and vnc access to a remote machine.

This is a much simpler method than many other tutorials I’ve found which generally suggest creating a tunnel with ssh -L and then using that tunnel.

Yesterday it was brought to my attention that the Gnome-Do team had released a major update, 0.5!  Being completely addicted to Gnome-Do I immediately upgraded to check out the new features.  Here is a basic rundown of the new features and, of course, how to upgrade your system!

Features

After taking a look at the mile-long list of improvements I realize that I won’t nearly have enough room here to outline everything.  I figure I’ll give you a link to the long list, and just outline some of the stuff that impresses me the most.

First of all I really like the new interface to handle the plugins.  Gnome-Do is a great tool, but a lot of the best functionality comes in the shape of plugins.  In the new version you’re able to manage all of your plugins by way of a central UI.  Activation, configuration, deactivation, etc all in one place.  Its a great way to try out all the plugins available without requiring manual downloading and setup, which was the previous method.

You really do need to check out all the plugins available–there are a bunch of new plugins that I’m sure you haven’t tried before.

You might notice, as I did, that some of the plugins you were previously used to need to be activated before they can be used again.  After you install (below) make sure to open the preferences and activate your favorites.

You can see an exhaustive list of additions at Dave’s blog, here.

How To Upgrade?

Now that I’ve got you interested I’ll outline how to upgrade.  In Ubuntu this is done by way of the Launchpad hosted PPA (Personal Package Archive).  This command will add the PPA repository to your sources.list:

echo "deb http://ppa.launchpad.net/do-core/ubuntu hardy main" | sudo tee -a /etc/apt/sources.list


Once you’ve got this added you’ll need to update (refresh), and then request the upgrade:

sudo aptitude update && sudo aptitude safe-upgrade

If you’re a new user you’ll definitely want to check out Gnome-Do with this release.  Install it using:

sudo aptitude install gnome-do


You should see an update for gnome-do at this point.  Accept the upgrade and the latest greatest version should install.

Thoughts?

I’d love to get some of your thoughts on Gnome-Do.  Do you use it as much as I do?  Hell, I don’t even have menu’s anymore.  I launch everything with Gnome-Do–everything!  Let me know what you think or share your favorite plugins.

I was discussing the creation and maintenance of an Ubuntu repository mirror in IRC today and realized that I haven’t blogged about how to do that.  Its funny sometimes how topics pop up, and something I’ve been using for months never made it onto the blog.  In any event, below I’ll outline how to create your own Ubuntu repository mirror–great for consolidating and saving bandwidth for multiple machines!

Creating the Mirror

To create an Ubuntu repository mirror we’ll use the apt-mirror tool.  This can be installed by issuing the following command or clicking the link:

sudo aptitude install apt-mirror

Once this package is installed you’ll need to configure a few items:

1. Where will your mirror be stored?
2. How aggressive will you be about downloading?
3. What do you want to mirror?

To edit these values you’ll want to edit the /etc/apt/mirror.list file.  I’ve displayed mine below, and broken it down into the three main sections.

Where Will Your Mirror Be Stored?

I’ve configured my apt-mirror to be stored on an external USB drive.  This is defined via the line:

set base_path      /media/gurudisk/UBUNTU/MIRROR

This overrides the default value, which stores the data in /var/spool/apt.

How Aggressive Will You Be About Downloading?

This title may be a bit misleading but this is the way I think about it.  Technically its the number of download threads you want to use.  The higher the number, the more threads, the faster its done.  This will depend on your bandwidth connection though.  On my home DSL I can’t put this number any higher than 2.  In faster locations you’ll be able to put the number much higher.  Your milage may vary.

set nthreads     2

What Do You Want To Mirror?

Now, the most important part, is what do you actually want to mirror?  The syntax for this section is pretty simple.  It looks just like a normal sources.list entry, but for each address you want to mirror.  Here is an example of my entry for Ubuntu 8.04, i386:

# Ubuntu 8.04 "Hardy" i386
deb-i386 http://archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb-i386 http://archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse

If you want amd64 bit mirrored you might add entries like this:

# Ubuntu 8.04 "Hardy" amd64
deb-amd64 http://archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb-amd64 http://archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse

Notice that I’m mirroring main, restricted, universe and multiverse plus the security, proposed, backports and updates sections.  This gives me a complete mirror of everything that would normally be available.  If you don’t want/need proposed or backports, etc you can simply remove those lines.

If you want to be able to use your mirror to support network based installations you’ll also need to add the following (depending on your architecture):

deb-amd64 http://archive.ubuntu.com/ubuntu hardy main main/debian-installer
deb-amd64 http://archive.ubuntu.com/ubuntu hardy restricted restricted/debian-installer
deb-amd64 http://archive.ubuntu.com/ubuntu hardy universe universe/debian-installer
deb-amd64 http://archive.ubuntu.com/ubuntu hardy multiverse multiverse/debian-installer

or

deb-i386 http://archive.ubuntu.com/ubuntu hardy main main/debian-installer
deb-i386 http://archive.ubuntu.com/ubuntu hardy restricted restricted/debian-installer
deb-i386 http://archive.ubuntu.com/ubuntu hardy universe universe/debian-installer
deb-i386 http://archive.ubuntu.com/ubuntu hardy multiverse multiverse/debian-installer

Basically just add the sources.list entry to this file for anything you want to mirror.  I also mirror Medibuntu and a few PPA locations.  It sure makes for faster installation when I am able to use the LAN as compared to the public tubes.

To keep your mirror updated activate the cron entry in /etc/cron.d/apt-mirror.  By default it will try to update your mirror at 4:00am, and it is disabled.  To activate it simply uncomment the line and change the 4 to the preferred hour of your choice.  Enjoy!

Update: My mirror, including main, restricted, universe, multiverse, -proposed, -backports, -security, Medibuntu and the network installation sections takes up 37G.  I do mirror i386 and amd64, so if you just need one architecture you could half-that.

Recently you may have seen this topic on Tombuntu’s blog, but if you missed it here is an outline of how to enable the advanced permissions dialog in the Nautilus file manager.

Activating the Advanced Permissions Dialog in Nautilus

Activating (or deactivating) the advanced permissions dialog can be done by way of a single command.  To activate the dialog use the command:

gconftool-2 --type bool --set /apps/nautilus/preferences/show_advanced_permissions True

To deactivate the dialog and revert to the default settings, use the command:

gconftool-2 --type bool --set /apps/nautilus/preferences/show_advanced_permissions False

Do you prefer one over the other?  The more advanced dialog reminds me of old permission dialogs in FTP clients I remember.  I think I may prefer it, but I haven’t used it long enough to decide.

You’ve been seeing a lot of virtualization specific posts recently here at Ubuntu Tutorials.  I’ve been tinkering with a number of virtualization options, namely VMware Server, Virtualbox and now KVM with Virt-Manager.

I’m not going to go into comparing the three in this post, but I will say that KVM is the only solution that will let me run 64bit guests on my 64bit host.  It also cleanly manages networking, whereas VirtualBox still has issues there.  KVM is still fairly new however so the UI features are not as nice as the other two.

Installing The Packages

Assuming your machine will support KVM (generally, core 2 duo and later) lets get the right packages installed.

sudo aptitude install kvm virt-manager libvirt-bin

This will install the Virt-Manager graphical interface for creating and managing your virtual installations.  It’ll also install the kernel module to make use of the KVM instruction set and the libvirt library.

Initial Setup

Once you’ve got the right packages installed you’ll need to give yourself access to the KVM device.  This is done simply enough using:

sudo gpasswd -a username libvirtd

This will require you to logout and login again.  When you get back we’ll get Virt-Manager launched and some virtual machines built.  Go ahead, relogin.  I’ll wait…

Running Virt-Manager

Virt-Manager is a nice kvm/qemu/xen management interface developed by the good folks at RedHat.  This utility makes it really easy to create, manage and delete virtual installations.  You can launch Virt-Manager via the command line, or the Applications menu.

virt-manager

Troubleshooting

If you have VirtualBox installed you may run into conflicts between the kernel modules.  Make sure to remember to remove the conflicting module before you run either of the virtualization solutions.  You can do this by using these commands.

To remove the VirtualBox module:

sudo modprobe -r vboxdrv

To remove the KVM module:

sudo modprobe -r kvm-intel

Enjoy.

Updated: added user to libvirtd group instead of kvm group. Removed launching with sudo.

Installing VMware Tools on virtualized guests gives you a much more enjoyable experience within your virtual environment.  Screen resolution, mouse behaviour, etc will be improved for your virtual sessions after installing these additional tools.  Installing these tools within Ubuntu 8.04 virtualized guests is fairly simple, just follow along below.

Installing VMware Tools

The first requirement, of course, is that you have Ubuntu 8.04 installed within VMware Server and that Ubuntu 8.04 is running.

Once you’ve got your Ubuntu 8.04 guest logged in, navigate to the “VM” menu option (File, Edit, View… VM) and select “Install VMware Tools”.  This will notify you once again that your guest must be logged in.  If that is the case, click “Install”.

note: The next step in the process may be simpler if you make sure any other CD images are unmounted before continuing.

This part of the process mounts a virtual CD image with the VMware Tools contained on it.  To find these tools for installation navigate to Places > Computer > CD Drive.  You should find these two files listed there:

VMwareTools-*.rpm
VMwareTools-.tar.gz


For Ubuntu guest installations we’ll want to use the .tar.gz file.  Now we have access to the needed file, the next part of the process is opening the archive and installing the tools.

Below I’ve put together a copy-paste list of commands you should be able to use to unpack and setup VMware Tools on your Ubuntu 8.04 guest.  All of these commands happen within the Ubuntu 8.04 Guest machine:

sudo aptitude install build-essential linux-headers-generic
cp /media/cdrom/VMwareTools-*.tar.gz /tmp/
cd /tmp/
tar xf VMwareTools-*.tar.gz
cd vmware-tools-distrib/
sudo ./vmware-install.pl


You should be able to safely select the defaults for most of the questions.  You might want to pay attention at the step where it asks for your preferred available resolution and set that properly.  For the new VMware Tools to be available once this process is done you’ll need to reboot your Ubuntu 8.04 guest.  Enjoy.