Matt's Linux Blog

Windows 7

2009-01-09T23:15:00.001-06:00

I’m posting this from a new Windows 7 installation, using Windows Live Writer. I really don’t have anything else to say right now.

Moving my RAID array to XFS

2008-05-01T19:23:00.015-05:00

I've got a 1TB RAID 5 array, which I use for backups. I use a script I made based on rsync, which pretty much mimics Time Machine functionality. That means in /storage/backup-lithium, there are directory entries for about 30 copies of my laptop's filesystem tree, even though most of them point to the same inode (i.e. data is shared between them). I've been using ext3 for this storage array, but I noticed it's really slow for searching through that crazy amount of directory entries, so I decided to try copying all my data to XFS to see whether it was any better.

Since I use LVM, this was pretty painless. First I shrunk my ext3 partition, which took a couple hours:

# e2fsck -f -C 0 /dev/storage/main
# resize2fs -p /dev/storage/main 400G
# lvresize -L 400G storage/main

Then I created a new logical volume:

# lvcreate -l 100%FREE -n xfs storage
# mkfs.xfs /dev/storage/xfs
# mkdir /xfs
# mount /dev/storage/xfs /xfs

I copied all my files from the ext3 to the XFS volume, which took about 22½ hours:

# time cp -av /storage/* /xfs

Now that I had two filesystems equally populated with directory entries, I ran bonnie++ and got very similar benchmarks on both volumes, suggesting that the change didn't really affect raw speed much. Then I tried something that would have to traverse the directory tree, with pretty drastic results:

# time du -sh /storage/backup-lithium
90G     /storage/backup-lithium
real    56m40.618s

# time du -sh /xfs/backup-lithium
86G     /xfs/backup-lithium
real    12m0.409s

The time it took to determine the total size of that folder went from 56 minutes to 12 minutes. To be even more sure of that result, I ran it again, giving me the same numbers within just a few seconds difference. I also noticed that XFS seems a bit more efficient at allocating files, since I confirmed that the contents of the directories were the same.

All in all, I think I'm going to mount the XFS volume as /storage and let the change be pretty much transparent. I've already checked to make sure that there were no files on /storage that were modified during the move. I'm not going to wipe the ext3 volume quite yet, since I still have plenty of space in the XFS partition — I'll do that when I actually fill up the disk.

LDAP Authentication in Ubuntu 7.10

2008-04-24T13:36:00.002-05:00

I recently acquired a file server machine, and I wanted to be able to use NFS to share files between it and my laptop. To do so requires that all users on both machines have the same numeric user IDs. I have a bit of experience with LDAP, so I decided to go for it.

I set up a simple LDAP tree under "ou=elements,dc=mmlx,dc=us", storing user accounts in "ou=People" and groups in "ou=Groups". I used "uid=username" as the RDN for users, and "cn=groupname" for the groups. Users are all of objectClass person and posixAccount. I made a group (objectClass groupOfUniqueNames) for each machine, containing the users I want to be able to log in. I also made a posixGroup called "ldapusers", to which all users belong.

Since one of my machines is a laptop, I set it up as an LDAP mirror, so that I can authenticate against localhost even when I am not connected to a network.

I installed libnss-ldap and libpam-ldap. I put the following in /etc/ldap.conf, and symlinked it to /etc/ldap/ldap.conf:


host 127.0.0.1
base ou=elements,dc=mmlx,dc=us
ldap_version 3
bind_policy soft
pam_groupdn cn=beryllium,ou=Groups,ou=elements,dc=mmlx,dc=us
pam_member_attribute uniqueMember
pam_min_uid 1000
pam_password md5
nss_base_passwd         ou=People,ou=elements,dc=mmlx,dc=us
nss_base_shadow         ou=People,ou=elements,dc=mmlx,dc=us
nss_base_group          ou=Groups,ou=elements,dc=mmlx,dc=us

Then, in /etc/nsswitch.conf, I changed the "passwd", "shadow", and "group" lines to:


passwd:         files ldap
group:          files ldap
shadow:         files ldap

At the top of /etc/pam.d/common-account, I added:


account [ authinfo_unavail=ignore ignore=ignore success=ok default=bad ]  pam_ldap.so ignore_unknown_user

At the top of /etc/pam.d/common-auth:


auth    sufficient      pam_ldap.so

At the top of /etc/pam.d/common-password:


password    sufficient      pam_ldap.so

I had read that adding references to pam_ldap.so in /etc/pam.d/common-session was also required, but I ended up commenting that out (unfortunately, I did that a while ago and don't remember why).

Then I tested the NSS configuration by using getent passwd someuser, where someuser was in LDAP and not the local machine. As long as that responds properly, you're good!

I used the following sources for this:
Making a Debian or Ubuntu Machine an LDAP Authentication Client
Re: [pamldap] pam_ldap for groupdn access control only?--Got it.
Need HOWTO for Ubuntu as an Open Directory client (LDAP/Kerberos/XServe)

D630 Gutsy 2.6.23.1 AMD64 Packages

2007-10-23T20:37:00.000-05:00

Seriously, the title of this post should contain all the information anyone would want to know except for, maybe, the URL. I've built packages from the official release of 2.6.23.1. Here they are: http://www.owlnet.rice.edu/~mmullins/packages/linux-headers-2.6.23.1-mokomull_2.6.23.1-mokomull-10.00.Custom_amd64.deb
http://www.owlnet.rice.edu/~mmullins/packages/linux-image-2.6.23.1-mokomull_2.6.23.1-mokomull-10.00.Custom_amd64.deb

I don't have any of the Ubuntu "restricted" drivers built, since the only one I need is ndiswrapper, and I do that by hand. If you need nVidia modules, well, I'm not very qualified to help you. Integrated graphics ftw.

Oh, and hi Dustin :-D

D630 AMD64 Ubuntu Kernel Packages

2007-08-23T18:00:00.001-05:00

Okay guys, I've finally made AMD64 kernel packages that fix the sound bug on the D630. They're available at http://www.owlnet.rice.edu/~mmullins/packages/

Huge Ubuntu Kernel Packages

2007-08-16T00:33:00.000-05:00

For all you D630 (and possibly D830) users running Ubuntu, I've been trying to make a kernel package that incorporates a working sound driver. I've been building packages with the stock Ubuntu configuration options, pared down a little bit (omitting IDE drivers and things that we'll never use), and I still end up with over 250MB of kernel images, which is about 80MB compressed! I can't figure out at all how Ubuntu kernels are compiled to have only 79MB of modules, uncompressed, giving a 17.6MB package. I'm *not* going to post an 80MB kernel package, so until I figure this out, you'll have to wait or DIY. I'll have access to webspace when I get to Rice on Sunday, so that's where I'll post what I build. This will all be unnecessary when 2.6.23 comes out, since the patch has already been committed.

Ubuntu and my D630

2007-08-11T02:13:00.000-05:00

Sorry for taking so long before getting around to writing this. I got my computer quite some time ago, and I'm now running Ubuntu Gutsy (the currently unstable version, due for release in October).

The main reason I'm using Gutsy instead of Feisty (the latest stable version) is because of the video drivers. My D630 came with the Intel X3100 integrated video, so I needed xserver-xorg-video-intel 2.0 or later to get all the new features. I also wanted to use the latest XRandR features, which allow me to dynamically add and remove displays, so I no longer have to restart X to go in and out of dual-head mode.

In order do this, I had to install using the Feisty alternative CD (the command-line installer), since the standard CD didn't have the proper X drivers. Then I upgraded to gutsy by changing all the "feisty"s in /etc/apt/sources.list to "gutsy", then issuing an "apt-get dist-upgrade". I don't remember the specifics of how I got X working, but I don't believe it took too much effort aside from upgrading to gutsy.

The only problem was with my Intel HDA sound card. The problem was a kernel bug, which has since been fixed. I'll post a kernel package as soon as I find a place to put it; right now, I have nowhere to host it. If you build your own kernel, open up sound/pci/hda/patch_sigmatel.c and change "spec->num_pins = 14;" to "spec->num_pins = ARRAY_SIZE(stac9205_pin_nids);" in the patch_stac9205() function (line 2182 in kernel 2.6.22.1, don't know about others). If you don't understand what I just said, wait until someone posts a kernel package, lest major kernel damage ensue. You may still have to reload the module after suspending (issue "sudo rmmod snd_hda_intel && sudo modprobe snd_hda_intel"; if that fails, then kill everything that's using the sound card).

Aside from the sound card issue, not too many problems have occurred. I'm happily typing this on my D630 now.

PHP, ASP.NET, and Java

2007-08-07T01:53:00.000-05:00

My main interest right now, like many people, is web applications. The top three tools I have seen are PHP, ASP.NET, and some amalgam of Java technologies. I have a recent infatuation with trying everything I can. I'm going to describe what I love (and more importantly, hate) about them.

Likes:
PHP:

Completely open source. I don't mandate open source software, but it is nice.
Very easy to host on a Linux system. I hear it also works in Windows, but alas, I have never even tried.
Customizable — it does what I tell it to do.

ASP.NET:

Extremely well-documented. I like the MSDN library, though at times, it can be too much information.
Easy separation of code and layout. I like being able to move "controls" around and having absolutely nothing change as far as the code is concerned.
It uses "controls", widgets that mimic Windows GUI elements (from the programmer's standpoint). At first, I thought it was a bad idea, until I realized I didn't ever have to bother with writing HTML for things.
It's very easy to use AJAX without actually coding JavaScript. I have nothing against JavaScript; it's just another technology I'm going to have to learn sooner or later.

Java:

It's open source (at least I think it is, now).
It is also well-documented. It's amazing how much commercial support helps documentation.

Dislikes
PHP:

Documentation of some modules is poor, misleading, or confusing.
Code and layout are strictly coupled. This leads to a really large mess of indentation and spaghetti code, since some blocks of HTML may be inside conditional/loop constructions, etc.

ASP.NET:

It's incredibly proprietary. Sure, there is Mono, but it only supports most of ASP.NET. One of its major exclusions (as of now) is AJAX.
There is too much documentation. I'm sometimes confused with finding certain documents.

Java:

It's simply too confusing. It's broken up into way too many pieces. It peeves me when I don't use something as it is intended; with Java, I can't figure out what piece is supposed to do what.

I would probably have more criticisms of Java if I could figure out how to use it. I'm sure it's great if you can reuse almost everything you program (or want to reuse it), but that's just not me. Right now, my platform of choice is Python using Django. Of course, there are some things I don't like about that too, but it would make for much too long a blog post (as if this one wasn't). I'm probably going to keep trying with Java, using that address book project as a test.

Switching to Java for the Address Book

2007-06-03T17:54:00.000-05:00

Yes, that's right, I'm going to buckle down and use Java for this project. The reason I decided to switch from C# and .NET is because I want to develop two user interfaces for the project: an application interface and a web interface. I only want to program the backend (the part that talks to the LDAP server, the "controller" in the model-view-controller scheme) once, and Java seems to be the most portable code I can use right now. Plus, .NET's directory [LDAP] classes were built for Microsoft's ActiveDirectory, and I'm using a self-designed OpenLDAP directory, which would be a large source of problems down the road.

I'm currently designing the class structure for the controller, and I'm making the large design mistake of implementing parts while still designing parts. I know this is generally a mistake, but I'm letting myself make it in order to learn what Java can actually do, so I don't design the whole thing like crap. I've found that once I got started in Java, it suddenly became less confusing, yet I still don't really know what I'm doing. I'll elaborate later, when I describe my design.

LDAP Lessons

2007-05-27T00:15:00.000-05:00

I've learned a couple things about OpenLDAP in the past day:

An object cannot belong to more than one STRUCTURAL objectClass
An object must have a STRUCTURAL objectClass
Don't do anything regarding authentication using an alias.
Weird things happen when you delete an attribute that objects use from the schema.
Use the "mail" instead of "email" attribute.
C# makes it quite easy to search an LDAP tree.

However, I'm currently having trouble getting a DN from a DirectoryEntry or a SearchResult. I can get the Path, which looks like "LDAP://server/DN", but I want just the last "DN" part. I could do a simple string substitution, but that seems like asking for trouble later. Help!

Making an LDAP Address Book

2007-05-26T18:09:00.000-05:00

I have taken on the task of creating a new networked address book for my parents. No one told me to do it; I took the task because I saw a need, and it gives me a perfect excuse to sharpen my technological skills. I have chosen LDAP to store the data. Usually, I would have used MySQL and designed a database, but LDAP allows me to have a hierarchical tree of objects, each node storing some data.

How is an address book hierarchical? In paper form, there isn't much reason for it to be. However, in electronic form, it makes perfect sense (to me, at least). Mainly, it's because families have children. That way, there can be one node for the family (a mailing address for "Alice, Bob, and Charlie Smith"). Under that, there will be separate nodes for Alice, Bob, and Charlie, which hold no address information, but may hold personal information about each family member. This way, it is equally easy to address an envelope to a family member as it is to address one to the whole family.

The main application of this address book (as many families' address books) comes around December, when it's time to send Christmas cards. Thus, I will be including a field ("attribute" in LDAP speak) called "sendCard", which will tell the application I build whether or not to print a label when it comes that time of year.

I have finished designing the hierarchy of the directory. The root is "dc=home,dc=mmlx,dc=us", which corresponds to the domain name "home.mmlx.us". I will have a subtree "ou=People" holding people represented in the directory, "ou=Users" holding entries for people that can use the directory, and "ou=Groups" holding groups for access control purposes. I'll draw up a nice diagram when I have time.

I'm about half done with the schema, which tells the database what data can exist for particular types of objects. I have designed the "mullPerson" object class, which holds the data one would expect to hold for a person. I am then going to define a "mullFamily" object class, which will hold address data, but not personal data. I'll publish those schema somewhere before I conclude the project, but if you want to see them now, just email me.

So far, I have found these to be good resources:

Understanding and Deploying LDAP Directory Services (ISBN 1578700701)
Unmasking the LDAP Search Filter

BestBuy revisited

2007-05-23T22:42:00.000-05:00

I received my restore DVD today, via FedEx 2-day. I took it in this evening to BestBuy, and got a very intelligent technician, who knew exactly which computer I was talking about. The conversation went like this: "Hi, I have these Windows disk that you needed for my laptop." "Oh, yours is the laptop with Linux on it? I'll take the disk and get started on it right away." He even stopped to mention that I had set my keyboard layout to Dvorak and that he could use it. Sharp guy. As I was walking away, he warned me to keep Windows XP on it because Microsoft will be discontinuing the product line.

I should have that laptop back in a week and a half to two weeks. We'll see.

BestBuy, Gateway, and Linux

2007-05-22T22:36:00.000-05:00

As you might have guessed, I had Ubuntu running on my old laptop. It is two years old now — bought it in May 2005, along with a two year service plan. In January, the USB ports died (motherboard issue, I guess), but since I was in school, I waited until last Saturday to bring it to BestBuy. I take it in, along with my PCMCIA USB card. I demonstrate quite obviously that a USB memory card worked in the PCMCIA card, but not the onboard ports. The tech simply asks me: "What version of Windows is that!?" I smelled problems.

I explained to him that I was running Ubuntu, which is a version of Linux, and I no longer have my Windows disks. That wasn't good enough for him. He explained to me that it was my responsibility to keep track of software, etc. I get the manager over, a process which took about fifteen minutes. He affirmed the poor tech's analysis, suggesting I call Gateway to get the disks. My warranty expires Thursday, so I wasn't about to wait for Gateway to send me disks. I suggested that they take the laptop and run their test suite (which the manager admitted was Linux-based) on it; he assured me that as long as they got the laptop into the shop before the warranty was over, the repairs would be covered.

Thus began the rather straightforward (but time-consuming) process of checking the laptop into their computer system. As I am about to leave, I mentioned that my power cord was flaky; he opened another ticket and told me to call 1-888-BEST-BUY. I did not at all expect this to be covered under warranty. He then offered me a $100 data backup service, which I declined, suggesting "You people couldn't do the backup anyway." Nope. I was corrected: they do have technicians who can use Linux to save files. Why can't these same technicians repair my laptop? Because the repair centers are somewhere on the West Coast, and those repair centers require the "original software." After this two-hour process of scaling the support tree, I can finally leave, without laptop or much hope of repair. But at least they'll ship me a free power supply.

I called Gateway immediately when I got home, and I ordered a set of recovery disks for $20. My manufacturer's warranty was only one year, so there was no way for them to justify reversing that charge in the computer — or so they claim. They shipped it FedEx 2-day; it should be here tomorrow.

About six hours later, I received a phone call: BestBuy had tested my laptop, and the onboard USB ports were indeed defective. Now they just need me to bring the Windows disks in. I am taking them in tomorrow (assuming they are delivered), so let's cross our fingers.

Dell Latitude D630

2007-05-22T12:36:00.000-05:00

Sometime in the next month, I should be getting a Dell Latitude D630. It's going to cost me $1488.43 (including S&H) for the following:

14.1" WXGA+ (1440x900) LCD screen
Core 2 Duo T7300 (2.0 GHz, 4MB L2 cache)
512MB DDR2-667 RAM
80GB harddrive
Intel GMA X3100 graphics
DVD writer
6-cell primary and 6-cell media bay batteries
3 year accidental damage coverage (CompleteCare)

And then I'm getting a 160GB harddrive and 2GB of RAM from Newegg, pushing the total to $1721.34. Not too bad, considering my other options were a Macbook and a Thinkpad, both of which had many fewer battery options available. It's going to be interesting using Ubuntu with this, since it uses a brand-new chipset (Santa Rosa, aka Mobile 965).

It's scheduled to ship on June 8.

Replacing Gentoo with Ubuntu

2007-05-09T22:50:00.000-05:00

I've used a wide array of Linux distributions since I started. First, there was DragonLinux, then came it's father, Slackware. Then I used RedHat (and then Fedora) for a while, but I got fed up with Fedora Core 2, so I moved to Debian. Since July of 2005, I have been using Gentoo, but now I'm getting fed up with even that. I've spent a couple weeks trying out new distributions to see which ones I like now.

What I want is a user-friendly system that has graphical tools for both standard end-user functionality and server functionality. I need a system that can run a decent server because I do a ton of web-application experimentation.

My main problem is that I hate something about every distribution. With Fedora, I hate the complete lack of support of any common media types. I ended up having to build my own RPM of w32codecs (so that I could play Windows media files), since everyone that hosts RPMs is scared of copyright and patent infringement. With OpenSUSE (10.2), I absolutely hated the excruciatingly slow package manager, and the fact I never could figure out when to use YaST or ZenWorks.

With Gentoo, I hate the extremely long time it takes to compile software. Also, there are no options for having a common setup already-built for me. Every time I want some software to interact, I have to set up myself. I could make my system into a wonderful system, but there are so many programs that I don't know can even interact.

I first used Ubuntu a year ago, since it was a Debian variant. I immediately liked it because it combined ease of use and ease of administration. I choose to use it now, as it is much easier to set up user-friendly programs, yet it is no harder to install a server onto than Gentoo was (it's actually a lot easier). I now use Ubuntu for my day-to-day work, but I am keeping my Gentoo partition around for my data. I don't plan to move my data over until I get my new laptop.

Welcome

2007-05-09T09:16:00.000-05:00

Welcome to my new Linux-centered blog. I will be describing many of the problems I face while using just about any technology. I will also post reasons for which I make the choices I make (such as PHP vs. ASP.NET vs. JSP, etc.) I hope you enjoy it (and that I don't give up blogging right after I start).