Firstly, create a new file called /etc/group.login.allow (it can be called anything - you just need to update the line below to reflect the name)

In this file, pop in all the groups that should be able to login

Edit /etc/pam.d/common-auth (in ubuntu), it might be called /etc/pam.d/system-auth or something else very similar. At the top of the file (or at least above other entries, add the following line:

For the record, found this little tidbit over at the centos forums\

In fact, we also considered GFS2 but looking around on the net, there seemed to be a general consensus recommending ocfs2 over gfs2.

Ubuntu makes it pretty easy to install and manage ocfs2 clusters. You just need to install ocfs2-tools and ocfs2console. You can then use the console to manage the cluster.

What I totally missed in all of my research and understanding, and due to lack of in depth knowledge on clustered filesystems was that OCFS2 (and GFS2 for that matter) are shared disk file systems.

What does this mean?

Wikipedia defines a shared disk filesystem as being “shared by being simultaneously mounted on multiple servers.”

This essentially means that the storage medium is mounted on to cluster. The cluster is a collection of the clients. The storage is traditionally a SAN mount point. This means that a shared storage space is accessed at high speeds by a number of clients.

From a simplistic point of view, this is not that different from mounting the SAN point onto a server and then running an NFS server on it with all the clients mounting over NFS.

The main difference is that OCFS is distributed. There is no single point of failure (assuming that the storage medium is redundant which a SAN would be). The NFS server is a clear single point of failure.

If you do not have access to or want to use a SAN, you can also use DRBD.

NFS is described as a network filesystem and GlusterFS is described as a NAS file system.

On the bright side, there are a few new things that have been worked on so hopefully plenty of things to cover soon.

We manage a number of servers and all over the place and all of them require to be backed up. We also have a number of desktops all with mirrored disks also getting backed up.

I like things to be all nicely efficient and its annoying when one server / desktop runs out of space when another two (or ten) has plenty of space. We grew to dislike NFS particularly due to the single point of failure and there were few other options.

We had tried glusterfs a few years ago (think it was at version 1.3 or something) and there were various issues particularly around small files and configuration was an absolute nightmare.

With high hopes that version 3.2 was exactly what we were looking for, we set up three basic machines for testing

Previously, glusterfs required all the configuration to be completed manually and with text files. It also required a fairly detailed knowledge of what they called translators and a lot of tweaking and fiddling with parameters.

I am very happy to report that this is no longer the case with 3.2.

The three servers(cserver[1-3]) are running Ubuntu and was updated to Natty (11.10) to get access to glusterfs 3.2 (11.04 only had 3.0). One thing to bear in mind is that the glusterfs website seemed to only have the 64 bit version but Ubuntu 11.10 also has the 32bit version.

Installing the server part of glusterfs was simple and straightfoward

Once this was done all three servers (terminator is a godsend when doing these things across a number of servers), adding the servers into a “cluster” was easy enough.

The thing to note is that these probe statements are two way. In other words, all three servers are now part of the same cluster.

The thing is that if you type in an incorrect hostname, the probe will keep trying to connect to it. I haven’t left it running long enough to know if it every returns.

Thankfully, removing host does-not-exist is simple enough

Creating a volume is straightforward. There are a number of different types of volumes which you can find out from the documentation. In this particular instance, we are creating a distributed replicated

The reason I have not included cserver3 in here is that the volume needs a multiple of the replica number of bricks. In the case, the there needs to be a muliple of 2 number of bricks.

Additionally, you could use rdma instead of tcp if you are using infiniband

Starting the volume is simple enough

this volume is now accessible from all the boxes in the cluster

Mounting this from another box is easy

If you get the error of “endpoint not connected” when listing the content of the mount, it is likely because the volume is not started.

If you are curious, check the gdata folders in the bricks after copying some files into the mount and you’ll find them show up intact and on both bricks in the above example.

Essentially what happens is that when I leave my desktop for a while, under specific circumstances, and often, on returning and moving the mouse or using the keyboard, the pointer would come back  on screen. However, this only works on one of my two screens.

The unlock dialog does not show up and it seems that there is no way to get back in.

In the past, I would log into the terminal (Ctrl-Alt-F1 or any function key through to F5 or so) and

This would of course kill all processes owned by me and is therefore unpleasant at best and have you losing a bunch of work at worst.

After a brainwave yesterday (as detailed in the aforementioned post), I decided to check the status of the screensaver and killed just those processes. Happily, this gives me my desktop back. However, my gnome-shell had given up which I had to restart

Unfortunately, I did not get the windows into the original workspaces since everything just got dumped into the one workspace but it is better than having to kill everything off.

EDIT: I just realised that the screen saver of course no longer kicks in and I had to restart it

I installed synergy on both ends, with the linux one as the server

and the mac as the client

http://sourceforge.net/projects/synergykm/

and it worked.

There was just one very very annoying problem. The Ctrl key and Cmd keys were different. This really messed with my muscle memory. After some hunting around, I just had to update my .synergy.conf file in linux. Here is the relevant section

et voila. It now works a charm. I  have neglected the configuration of the synergykm and synergys but these can be figured out easily ;-)

Being a bit of a purist, I ran Debian{for very many years but found their stable releases lagging behind far too much. This was largely due to their perfectly understandable view of it being ready only when it is right.

For a while, I ran their unstable distribution called Sid{ based on the disturbed, hyperactive 10 year old boy in the film Toy Story{ The idea being that Sid breaks things, and it certainly did. While it taught me a heck of a lot about linux (and the terminal), my computer was broken on a very regular basis.

I switched down to the testing version and that helped ease the pain to a very large extent. I had always thought that Debian with a more regular and shorter release cycle would make a world of difference. Clearly, Canonical had the same idea.

Thus Ubuntu was born and it has grown from strength to strength. Its latest distribution of 9.10 codename karmic koala released October 2009, is a massive step forward.

Stephen{ the head of krayatec{was so impressed by the new release that he conducted an experiment. He asked three people in the office who are not tech savvy to install and try out the new release. My view was that it was still too early for such kind of an adoption. I felt that pushing people to try it out at this stage would damage the reputation of the user friendliness of Linux rather than help it.

I must admit that I was proven wrong.  All of the installations went smoothly and it was possible to log in and do the things that they wanted to do.

Do they now use Linux instead of Windows - No! There is still a learning curve and with tight deadlines and little time for re-learning how to navigate around a computer, it remains an experiment.

However, it does answer one question. Can a user who is not tech-savvy, pick up a CD/DVD of the latest version of Ubuntu and run with it? The answer, from this very tiny experiment is a resounding Yes!

As someone who is technically very demanding, I have very few complaints about the latest version. The only one is that it still looks largely the same as the previous version. Then, the release is a collection of tools, so this is understandable.

My three favourite things about the new release are:

• substantially faster bootup times
• Empathy (particular for people-nearby which works great in the office)
• Cloud (Client & Server)

In my opinion, this is the beginning of the end. Linux, has finally taken a leap that shows its potential to change everything… I would wish it luck, but it looks like it doesn’t need it ;-)

Why not download a live cd and try it out?

I needed host networking to be able to access network resources (Samba shares etc.) which does not work if the guest OS is on NAT :-(

Solving it was easy though… I assume Vista is installed as a guest with the guest additions and that your user account is a part of the vboxusers group.

On the linux host, first install bridge utils. I run Ubuntu, so it was as easy as:

Next, you need to set up the bridge; again, easy on Ubuntu:

add the following section to /etc/network/interfaces

Add the interfaces to VirtualBox

Within the VirtualBox Guest settings, choose Host Networking and fo the interface, choose br0

bring the interface up:

and start your guest os… et voila, it just works…

We are not necessarily controversial, just that we hold a view that is usually a little different from the mainstream views. It could be said that we bring the alternative to the mainstream.

But then, so did some world governments, bringing open source software into their work places, successfully or unsuccessfully in the last few years instead of Microsoft.

Someone recently suggested that we were anti-microsoft. I don’t think that is case. Microsoft has its place in a technology infrastructure. It is simply that its position is usually overrated or misplaced. As far as desktops for technically shy users are concerned, there is really no alternative but Microsoft Windows. I can hear the Mac users scream that Macs are also an alternative. Theoretically, yes but the fact is that they are too expensive for someone to dabble with it. This is precisely the reason that Microsoft Windows dominates the desktop market.

We support and use Linux. In fact, the majority of the desktops in the office run Linux (Ubuntu as it happens) but people who have a non-technical role use Windows. They could use Linux but Windows is better suited to their role.

This is not necessarily a cost-saving decision. Sure, we have saved thousands of pounds by sticking to Linux instead of using Windows but that is a co-incidence more than anything. In some ways, it is a testament to the skillset of the people who work at Kraya that they are comfortable with Linux. The mindset of Linux is in alignment with the mindset of a developer.

I used to develop in Windows and I often found myself fighting with Windows, whereas with Linux, it just fits. There are several reasons for this. One being that Linux forces you to understand what you (trying to ) do to a bit more depth instead of pretending its magically taken care of.

I am not, for one moment implying that developers who use or develop on the Windows platform is inferior or not as skilled. Simply that my experience was that the Windows platform made it easier to do things badly and more difficult to do things well.

Microsoft has done wonders in bringing technology to the masses and making it more accessible. However, there is still a massive barrier, even for people specifically in the technology sector to appreciate and use technologies which require a bit more experience or knowledge to use appropriately.

There are a couple of really good examples. PostgreSQL is a powerful outstanding database server that can easily compete with Microsoft SQL Server and Oracle. However, very few people know about it and even fewer use it.

MySQL on the other hand is also an open source database server but is much more widely used and accepted.

It surprises me when MySQL is used when PostgreSQL is, from a technical perspective better suited. MySQL is faster than PostgreSQL at the cost of poor transaction managment (at best). For any system where data integrity is even remotely important, PostgreSQL is a better choice. However, since there are better GUI tools for MySQL and since it is easier to get the hang of, it gets chosen.

This give technology and people in that sector a bad name. Every tool or software has its place, and should be used in an environment where its strengths are displayed, not its weaknesses. We have instances where we use multiple database servers within one project. PostgreSQL for all the data integrity sensitive areas and MySQL for the speed sensitive areas. Sometimes you want integrity and speed. In these cases, you have to make a choice based on which is more important or layer the databases to use the strengths of both.

Metaphorically speaking, MySQL is a hammer, and PostgreSQL is a sledgehammer. Would you use a sledgehammer to crack a nut, or a hammer to crack a slab of concrete?

Before someone jumps down my throat, I am not suggesting that PostgreSQL is better than MySQL or vice versa - just that they both have different goals, different strengths and weaknesses. They have spent a lot of effort to converge and strengthen their weaknesses but not matter the amount of convergence, their core goals are still different that they will never truly be able to remove their weaknesses without giving up some of their strengths as well. One tool cannot be both a hammer and a sledgehammer…

In the open source world, I expect that all things which are accessible as 32bit are also accessible and 64bit and ubuntu makes it automagic enough that everything just works. Yes, I run into problems with closed source software like Flash Player (recently resolved with flash player 10) and the Java Plugin but that is another story. I use Eclipse and wanted to do some performance analysis and benchmarking to find a bottleneck and installed the TPTP plugin; and ran into a problem. It just didn’t work.

To resolve it, I turned to google… In this instance, it turned out to be a distraction and a red-herring. It lead me in the direction of installing libstdc++2.10-glibc2.2_2.95.4-27_i386.deb which was difficult at best since there was only a 32bit version of the package and that wasn’t even in the standard repository.

In the end, digging deeper, I found that it simply missed the following shared object libstdc++.so.5.

All I had to do was install libstdc++5:

and it worked… :-D

Now, I think that ACServer which Eclipse uses to do TPTP should not link to an outdated library but that is another issue…