STSE Supercluster

I’ve spent the last few months picking at a FreeBSD clustering project. Well, with some help from BSDHound and the Central Iowa Linux Users Group (CIALUG), it’s finally complete.

I clustered 4 Pentium 133s running FreeBSD 5.1-Release using LAM-MPI for the messaging interface and Ganglia for the monitoring. You can view the statistics here, but you must be registered and signed-in to do so (the pages are fairly graphic intensive).

I believe there will be a clustering How-To posted to in the future, and if it is, I will be sure to post and update here.

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Fixing fstab Problems in FreeBSD

I made a bad decision that resulted in a non-bootable (to single user only) FreeBSD system. Now I realize that no one really cares what kind of jam I’m in, just like I don’t normally care what kind they are in. But when you have to sit through some ‘open sourcer’ stroke his own ego with the “I know something or where to find it, and you dont. I know its a simple question to answer quickly, but Im just gonna post tidbits of a manpage out of context” attitude, it really irritates me.

I use alot of opensource and I try to avoid doing that to others (usually successful), as well as avoiding the “the distro I use is better, so you should just switch to fix your problem” answers. There is definately reason to read the documentation, but at some point its just proper to be upstanding and state “such and such should fix your problem, when you’re back up and running make sure to look at the manpage”. Their normal excuse is “I’m sick of answering all these newbie questions that are in the clearly addressed manpages”. To that I say, THEN GET OUT OF ?N*X SUPPORT CHANNELS.

Anyway, I digress. Now to the real problem, me blowing up my /etc/fstab and how to fix it, in case it happens to you!

I started a forum thread entitled “Opensource Attitudes” to address the rant portion of this. If anyone has any questions about the technical side of this article, feel free to start a thread in the appropriate forum.

So the faulty decision I made was to add a USB jumpdrive to my fstab. I wouldn’t recommend this :)

To fix the ensuing cluster, I did the following:

1. Rebooted into Single User Mode
2. Mount (to see whats mounted and how)
3. cat /etc/fstab (to see what filesystems I normally mount)
4. mount /dev/ad0s2a /usr (to get my utilities, namely vi)
5. mount -u -w / (This mounts / writeable so you can save your new fstab)
6. vi /etc/fstab to remove your bad entry or whatever it is that was changed
7. reboot

At this point everything should be back to where it was before the fateful edit, if not, just repeat the steps above until it is.

It’s also a good idea to make a copy of your /etc/fstab in case it’s fat-fingered yet again. That way, you can at least see the way it was previously broke (better yet, make a backup before your initial edit of the working copy… lesson learned)

Hope this saves some of you from the open-source ego-trip, at least for fixing your file systems.

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