Digital Arts Service Corps - Linux

Working hard on things that are hardly working

Josh King — Fri, 13 Jul 2007 19:24:08 +0000

It's been an uphill battle this week with our internet service provider, who has been doing maintenance in this area resulting in major outages for Acorn's Chambana.net datacenter, along with all of the other network services in the building. Between me and my supervisor we've probably spent about 4-5 hours on hold with tech support over the last couple days. There's been a lot of talk about switching to some other ISP instead of Insight, but most of our options are significantly more expensive for little more capacity than what we already have. We are still hoping to get a deal with the city of Urbana for a fiber connection into the building, but that seems to have stalled for the time being. On the bright side, we've managed to find a couple of really nice 42u racks for only $100 a piece (these are worth more like $800) that belong to a friend of the project, and so we're going to be moving those into our server room soon, and it'll be a lot better than having our servers sitting on crappy wire shelves or on the floor. Still a lot of work to do getting Chambana.net up to spec, but I hope by the end of the year we'll have completely fast and redundant hosting services on real racks with gigabit ethernet, a fiber connection, battery backups, good electrical, physical security, HVAC, and good distributed management/monitoring capability. We hope to have our main website updated in the next couple of weeks, and I'm going to try and integrate all of our services into that drupal installation, including a donations page and a ticketing system.

On the wireless side of things, soon we're hopefully going to be getting a research grant from the NSF. We'll be able to do a lot of development and even a little hardware deployment with the money we'll get. We've also got a tentative deployment plan with the city of Urbana that will deploy three more nodes, after which we'll have all of the outdoor seating areas in the downtown provided with public wifi hotspots. We need to move fast on this because Urbana's adjoining city of Champaign just announced a deal with a company to deploy a proprietary wireless tech in their downtown, and we don't want them to beat us to the punch when we've been working on our grassroots OSS solution for the last three years.

Finally, got my loan forbearance and am applying for foodstamps, so I should hopefully squeak by at the end of the month here.

Xen: Instant Karma

John Miller — Wed, 31 Jan 2007 23:06:26 +0000

Imagine if you could run Windows XP, Mac OS X, and multiple versions of Linux on the same computer. That's already a reality--you just have to reboot to switch between them. Now imagine that you could run all these operating systems at the same time on the same computer. You could run MS Word 2003 at the same time you're running Safari, all while programming in Eclipse. It's possible. The technology that makes it possible: Xen.

Xen is a virtualization technology that's based on Linux. It lets you run multiple virtual computers ("guest" operating systems) on top of one master operating system (called the "host" OS). In other words, you can run Windows and Linux on the same PC at the same time.

That's the sexy use, anyhow. Xen's already in use by hosting companies to give customers their own computer. Instead of having to give customers a physical PC, Xen allows the hosting companies to fit many virtual computers onto one PC. If the customers don't need much computing power, why not?

At the Community Software Lab, we're in the process of putting together a Xen-based server so that we can emulate our current network of servers from within one machine. Instead of having to prepare a new computer to become a server--install hard drives, memory, network cards, cd-rom drives, load the OS via cd-rom--we can type a few commands on the Xen server and have a working virtual computer in about five minutes. What once took a day to do now takes minutes.

The kinks? The Xen server has to share its memory among many virtual computers, and these days, people's personal computers use 256 MiB, 512 MiB, 1 GiB, or more. This puts a limit to the number of virtual computers that can fit onto one host machine.

We're working the kinks out of our test server (now running computation-friendly virtual machines), and as soon as we hear from our server supplier, we'll be putting together the production server.

Computer virtualization is nothing new, however. IBM's been doing it in their mainframes for over 40 years. VMWare is a widely-used virtualization product. Various video-game emulators have been around for a while (I beat Rygar using good ol' Nesticle, all while surfing the web). Xen just seems most promising for the moment.

I would be remiss in my duties if I didn't mention KVM (Kernel-based Virtual Machine--not Keyboard, Video, Mouse!). New in the 2.6.20 Linux kernel (the core of the operating system that handles memory management, task switching, networking, etc.), KVM might give Xen a run for its money. I'll try it out, but with time invested in Xen, that's where we're headed for the moment.

Dancing with Samba

John Miller — Fri, 06 Oct 2006 23:47:40 +0000

Over the past two weeks, I've been putting together a server so that people across the street from us at UMass Lowell (we're on-campus also) can mount their website files, hosted with us, as a network drive under Windows. This can be done with FTP, but it's still a bit messy. Fortunately, there's software out there, called Samba, that lets you make a Linux/Unix computer act as a Windows server. Here's how we've used it.

The first step is to set up a computer running Linux/Mac OSX/FreeBSD/NetBSD/Solaris... (any Unix flavor). This is a whole blog entry unto itself, but these days, it's not too hard, and it's getting easier and easier every day. Here at the CSL, we have a fairly well-established checklist for doing this, but there are always minor kinks in the process. Since our income is fairly small at this point (getting larger, thanks to some new grants and kind donors), our equipment is mostly hand-me-down. In this case, it meant learning about a new server we'd never spent much time on (memory on it must be installed in pairs!).

Once you have a computer running some form of Unix, you need to install the Samba software. For us, that means going to the command-line (GUI on a server? No Way!), typing:

apt-get install samba

and going through a few prompts. We use Debian GNU/Linux here at the lab, so your install procedure may be different.

I found helpful resources for the install part at:

So now Samba is installed, but it doesn't work right! Surprise, surprise. How could it possibly come pre-configured for everyone? To make things work properly, it means editing a file called smb.conf. In our case, this file is located in the /etc/samba directory, but again, your mileage may vary. You can either edit the smb.conf file directly, or you can edit it using a web-based tool called SWAT (Samba Web Administration Tool). I mostly edited the smb.conf file directly, but getting SWAT running was kind of fun, too.

So how to edit smb.conf directly? My preference is to use an editor called vi, but again, you have all kinds of choices. Some people may prefer to use emacs or Notepad (if they're the Windows sort) or TextEdit if they're on a Mac. Just has to be a text editor.

How to use SWAT? It has to be running, first of all. The easiest way to check is to open a browser and type in:

http://your.server.name:901

That's right: SWAT is a web server running on port 901.

If SWAT's not running, don't fear: it probably just means uncommenting a few lines or adding a few lines in your inetd.conf or xinetd.conf files. In my case, I just uncommented a few lines in /etc/inetd.conf and restarted the inetd process with:

/etc/init.d/inetd restart

But that's all I know right now about SWAT!

I won't go into much further detail about editing the smb.conf file, because I need to eat dinner, but there are some sections that govern the server's operation, and then you have one section for each file share (thing that becomes a network drive under Windows).

If this sort of thing interests you, and it should if you're wanting to avoid dishing out money for a Windows server license and want to learn more about Unix/Linux, here's a full list of resources, with descriptions, that I've used:

samba.org: The official site of the Samba project, samba.org has plenty of documentation on every Samba option under the sun. You can find the Samba manual as well as several e-books, including O'Reilly's Using Samba, which I found to be readable and easy to follow.
aboutdebian.com: This is a good website for people new to Debian GNU/Linux or for people who have never set up a particular type of server (like Samba!) using Debian.
linuxhomenetworking.com: This site is the much more complete version of aboutdebian.com. The author goes into extensive detail about how to install and configure web servers, file servers, logging servers, DNS servers, and many more, using Fedora Core (Red Hat) Linux. Very applicable.
Google: Everyone knows about it, everyone uses it, but I've yet to find a better place than Google to search for error messages.