Designing the perfect Linux Server isn’t difficult, it can be time consuming but with a plan, you should be able to get everything running quickly.  This post will lay out the groundwork of what services the server should provide and how we divide it up among our virtual machines.

The main services that I want the server to provide are web, ssh, mail transport, dns-caching, and file serving. Some additional, but non-essential tasks could be bittorrent, ftp, streaming media, and VPN.  Of course their are a ton of things you could add to this list, but these are the services I feel are the most useful.

The next step is to list the applications that we will need to run to accomplish these tasks.

• Web Server
  • Apache
  • Mysql or other database is usually necessary
  • PHP
• SSH Access
  • open-ssh
• Mail Transport
  • I use Qmail, but there are many options
• Dns Caching
  • I prefer Tiny-DNS, Bind is also a good choice
• File Server
  • Samba
• Bittorrent
  • rtorrent
• FTP
  • I use SSH for file transfers and you should to
• Streaming Media
  • Lots of options, ampache and Jinzora are who popular ones.
• VPN
  • OpenVPN

Some other services that I install to keep an eye on things

• Munin
• Nagios

So how do we divide these systems up.  The choice is yours, but for this tutorial I am going to use the following setup.

• Zeus: Domain0.  This is the top level system that all other servers run on top of
  • Xen
  • Qmail-send
  • Munin-node
  • SSH
• Pegasus: Web Server
  • Apache
  • PHP5
  • Mysql-Server
  • Qmail-send
  • Munin-node
  • SSH
• Hades: File Server
  • Samba
  • rtorrent - This makes the most sense here as we will want to access the files downloaded from other systems
  • Qmail-send
  • Munin-node
  • SSH
• Athena: Monitoring and support services
  • Tiny-DNS
  • Apache - To allow for remote viewing of system status
  • Munin
  • Munin-node
  • Nagios
  • Qmail-send
  • OpenVPN

A few things that I need to point out in regards to this list.  First, I actually installed Samba on Pegasus(Web Server) so I can edit my development files dirctly.  You could host things on Hades and just mount the share under your web root if you wished.  It also would make sense to do all development on a seperate server, I don’t due to the limitations of having one IP address.

A few other points, I don’t actually run an SMTP server on any of my servers.  I use Google apps to receive and store my mail.  Qmail is only installed to send mail from the servers.  It is trivial to install qmail-smtp to allow you to receive mail.  Another change that I would make if I had better hardware would be to seperate the system running apache from the system running MySQL.  This is mainly a security enhancement but is not extremely important.

This site is run out of a server that sits in my basement.  I used to host my websites on a shared web host like GoDaddy, but after spending almost $100 a year and having very little control over my hosting service, I decided that I could run most of my sites from my home.  Of course I don’t get a lot of traffic so this is possible.

Recently however I started to attract some extra traffic here and there.  Nothing major, maybe an extra 25-50 hits a day, but it got me thinking about what would happen if I happened to claw my way to the front page of Digg .  A massive spike in traffic would most likely result in my site crashing.  I can protect myself from this the best I can; tune apache, setup opt-caching, setup caching on Wordpress, and other modifications.  Unfortunately, these can only help so much though when my server has a Sempron 2800+ with less than a GB  of memory.

So I decided that something had to be done, I considered a few alternatives, but as I looked over the software and hardware landscape, I decided to focus on virtualization.  I decided to purchase some additional memory and setup a Xen hypervisor.  There are several benefits to this.

1. If my server was brought to it’s knees, I am be able to ssh into my system and hard reboot remotely.
2. Improved security as I currently run numerous services on my server.  I can isolate my internal services from the external services.
3. I can setup monitoring, and receive alerts if a service or host fails.  Without Xen, if my host failed I wouldn’t receive alerts as the monitoring system was down.
4. A great learning opportunity and a chance to write about it.
5. It makes sense financially. I spent $50 on memory, which is cheaper than most hosting programs.

For those of you who don’t know, Xen is a virtualization technology that allows you to host “Guest” operating systems on a single piece of hardware.  You have your initial OS that you boot into as you normally would, then you can boot additional systems on top of the original system that independently.  These systems are fully operational and can do pretty much anything a non Guest OS can do.  The systems share the available hardware resources but the performance hit is minimal.

Throughout the next few weeks I will be putting up a series of posts that will describe the steps it takes to create what in my opinion is the ultimate Linux server.

Sorry for writing another Twitter post, but it’s currently my favorite application.  I have been spending quite a bit of time trying to find the best Twitter client.  As I run an AMD64 version of Ubuntu, many of the great Adobe Air client’s are not available to me.  And to be honest, the Twitter clients that are available for Linux just aren’t that great.

I fought with Adobe Air for a while but finally gave up.  Hopefully Adobe releases a 64bit version of Air soon because I would love to try out some of the apps on that platform.  In the meantime I discovered a wonderful way to use Twitter in Firefox.  I started using Hahlo last week.  I also have Twitterbar installed in Firefox.  Until today I was using Hahlo in a tab, but I realized today that this website was a perfect candidate for being loaded in the sidebar.  How do you do this you may be asking.  First add Hahlo as a bookmark.  Then go to the bookmark and right click and choose properties.  You will see an option on the bottom of the screen saying “Load this bookmark in the sidebar”.  Check that box, load the bookmark, and you have the result on the right.

Now Hahlo is great, it has a few small issues, but nothing major.  For some reason whenever I start following someone in Hahlo device updates get turned on.  But for following your twitter storylines it rocks.  You can tweet in Hahlo but I don’t really like the interface for some reason.  To remedy this I installed Twitterbar.  This extension allows you to post to Twitter using your address bar in Firefox.  Just type your tweet into the address bar and hold your mouse over the dot on the right side.  You will get feedback on how many characters you have left.  Click the dot and it posts to Twitter.  This makes more sense than it sounds I promise.  Give it a try, you might like it.

Oh and follow me at Twitter http://twitter.com/sloped

I just discovered this wonderful conky tutorial at Linux Owns.  I am planning on writing up a tutorial combining this one and my Compiz tutorial so it works well in Compiz.  Of course if you don’t use different wallpapers on each desktop, linuxown’s tutorial is a good starting point.

Linux Owns - Create a Custom Conky Setup

When was the last time you knew what was normal for your server?  Have you ever had a suspicion some process was eating up your resources? Ever left for vacation and want’d to know if your web server went down?  These are some of the questions that a good system monitoring application can help answer.

Before I left for vacation I installed Munin and Nagios.  These are two mature system monitoring applications.  Munin keeps track of various bits of system information; the number of apache processes, system load, mysql queries, and other useful statistics.  Munin’s benefit is it keeps a historical record of system status and displays it in graph format over day, week, month, and year.  This can allows you to monitor your servers to determine if anything out of the ordinary is occurring.

Nagios is well suited to monitoring your system and services to determine if there are problem and send alerts if detected. It can monitor your apache services, ssh, disk space, and other critical apps.  Though Nagios does allow you to review some historical data, Munin is better suited to this task.  When I first installed, Nagios was configured to monitor http, ssh, root disk space, processes, number of users, and swap space.  These were sufficient for my needs, but it didn’t setup alerting.  I was kind of short on time, and Nagio’s configuration is complicated, so I didn’t get alerts setup before I left.  This defeated the purpose of installing Nagios to monitor my server while I was on vacation but I could still log in and check my system status if I wished.

One caveat to consider when installing Nagios on a single server, if you are monitoring the localhost and something goes wrong which makes the system inaccessible, it doesn’t do much good to get alerted to the problem.  The best approach would be to setup a separate monitoring system.  Using Xen or another virtualization product would be a good idea in the case of a single piece of hardware.

Remember that even with good monitoring software installed, Murphy’s law applies.  This means that your monitoring system will fail before any of your other systems.

Here is an oddity in Samba that I ran across tonight. I was working on updating my mp3 player for my trip home. I wanted to transfer over some AFI, but when I went to view all the albums I had available, only one of my albums was visible. I logged into my music server and browsed to the appropriate directory. I had three directories, AFI, Afi, and A.F.I. Looking in them, A.F.I had the album that was visible in Amarok, Afi was empty, and AFI contained the missing albums.

Thinking that was odd, I opened up the drives under nautilus and browsed to AFI, this showed all the albums, then I browsed to Afi. Surprisingly it contained all the albums to, but when I tried to play a song in the directories I received an error.

A quick google search brought up this. I appears that Samba by default is case insensitive to work with Windows. So when it translated Afi and AFI, it listed the files in both folders, which had the side effect of causing some odd problems with my music collection.

It was a simple fix, originally I had this configuration:
[media]
comment = Media Drive
path = /media/storage
read only = yes
write list = conner

I added the appropriate configuration directive:
[media]
comment = Media Drive
path = /media/storage
read only = yes
write list = conner
case sensitive = yes

Then I restarted samba and my problem was fixed. One caveat is that if you were accessing the drive using Windows, there is a possibility that this could break some things, so be careful and test.

Note:  I know I could have deleted the empty directory, but I wasn’t 100% sure that the problem didn’t exist in other parts of my collection.

Can we all please agree to stop doing this?  From here.
sudo chmod 0777 /var/cache/eaccelerator
Why in the world would you do this? It is  saner and more secure to set the directory owner to the user your web server runs as.  Yes, in this case it probably won’t make much difference, but I don’t know how many times I’ve seen tutorials and forum posts that state, “oh, just run chmod 777 on that directory”

I understand that making your tutorials easy to follow is important.  Still, could we all at least make an effort to recommend that instead of running chmod 0777, that the user change the ownership to the appropriate user or group?

Oh and in the case of the above tutorial, the appropriate command should have been:
sudo chown www-data
Then, only root and the webserver have write access to the directory.  Much better than allowing everyone full access.

I bought a multifunction printer last week, the Brother MFC 240.  I didn’t buy it for the printer, I purchased it because it was on sale and had a 10 page auto feeder for the scanner.  I’m working on moving to a paperless life and decided that getting a scanner and moving all of my documents to pdf was the way to go.

Installing the printer on Ubuntu 8.04 was fairly painless.  I followed these instructions for the most part, though I didn’t attempt to setup the scan button.  It’s nice that Brother supports Linux and it definitely made it easy to get the printer and scanner up and running.

To scan I use Sane, it’s a solid program if not pretty that does what you need it to do.  I set it up to scan each page and just save the image to the appropriate folder in my home directory.  This way I can just put the documents in the scanner and walk away.  I scan into the pnm format, with the resolution set at 300×300.  I then use ImageMagick’s convert program to shrink and convert to pdf.  Here is the bash command I use to convert a folder of images to pdf.

for i in $(find . -iname ‘*.pnm’); do convert $i -resize 50% -compress Zip $i.pdf; done

This cycles through the current directory and finds all files ending in .pnm. Then it runs convert on each of the results, resizing the image to 50%, converting to pdf, and compressing it using the Zip format.  This results in a decent size pdf at about 2-3 MB per page.  There are probably better ways to do this, and unfortunately this doesn’t end with the text search able, but for my purposes it does the job.  I’m sure I will perfect my method as time goes on, and may play with ocr soon.

This past weekend I kept myself pretty busy.  First I went to the monthly meeting of Penguins Unbound.  There, I listened to Paul Cutler give a talk on Foresight Linux.  This was interesting and getting out and trying to become involved in the Linux community in the Twin Cities is definitely something that I am going to continue.  Listening to someone who is involved in the decision making for a successful distribution was great and I felt that I have a better understanding of how much work goes into maintaining an established distribution.

The second part of my day was taken up by driving to Cannon Falls and biking the Cannon Valley Trial.  It was great, the trail is well maintained, there are a ton of rest stops along the way, and it’s tree covered so you don’t get fried when you forget sunscreen, as I did.  When I started the riding I planned on going about 15 miles and turning around, thinking that 30 miles would be about all I could do, but by the time I hit 15 miles I decided to just continue to the end.  So I ended up riding 40 miles total on Saturday.  I was exhausted at the end of it, but it was a great way to spend the afternoon.  If you are in the Minneapolis/St. Paul area, I highly recommend making the trip to Red Wing or Cannon Falls and taking the trail.  It is $3 for a wheel pass, but it’s worth every penny.