Dark-Fx.com

disks: Current state of the mythbox
2009-08-25 13:48:10 posted by Dark-Fx
Well it's been a few years since I last posted about the state of drives and such in the mythbox, so now's as good a time as any.

Previously I had been running software RAID5 on the mythbox with 6 500G disks. These disks are still around, but are now accompanied by a 3ware 9650SE-12ML hardware RAID card and 6 more drives, all in RAID6. These disks are accompanied by 4 750G disks in software RAID5 hanging off the onboard controller. I haven't done anything with the second array yet as it's a recent addition that was previously left out due to lack of space in the case. Running 16 hard disks in a single case requires a purpose built case.

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              19G   15G  2.6G  86% /
/dev/sdb1             4.6T  2.7T  1.9T  60% /myth
/dev/md0              2.1T   75G  2.0T   4% /myth2
As you can see, I have more than enough space, at about 6.7 Terabytes usable with only 2.7 Terabytes used.

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Linux: Forcing a system reboot
2008-12-10 09:33:50 posted by Dark-Fx
One of my machines has been having problems where the disk that / is on has been dropping out. This is especially irritating because I can no longer properly execute any commands, including the reboot command like so:

mythbox:~# reboot
-bash: /sbin/reboot: Input/output error

Clearly I wasn't going to be able to reboot my computer normally. Luckily I remembered about the magic sysrq way of rebooting. Unfortunately, I didn't think this was going to help because I'm 10 miles away from the machine, and can't get to it for another 7 hour or so. I dug in to how the sysrq stuff works, and you can do it on console by echoing to it.
echo 1 > /proc/sys/kernel/sysrq
echo b > /proc/sysrq-trigger

Running these commands forced a reboot on the machine and it came back up happily.

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Christmas: List
2008-10-11 20:42:00 posted by Dark-Fx
This is the list of stuff I wanted last year; what I don't need or already have is striked out. New Stuff:

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IRC: Servers I hang out on
2008-04-16 23:11:23 posted by Dark-Fx
I hang out on quite a few different IRC servers and get asked about what servers they are, so I'm putting this info up here. I don't generally disconnect at all, and I set the channels up I frequent to autojoin.

irc.acns.msu.edu
irc.zarquon.org
COFFEE.OFDOOM.ORG
irc.efnet.org
irc.freenode.net
irc6.foonetic.net
mtulug.fxaffinity.com (or lug.mtu.edu)

I may update this list as needed...

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Disk Images: Mounting partitions from dd hard disk images in Linux
2008-04-09 22:55:42 posted by Dark-Fx
Okay, So you did a dd copy of an old disk you were using and just now need to grab something off of one of the partitions. You have a few choices of how to do this. You can use dd to copy just the specific partition out, or you can mount that partition as a loopback device with losetup. The latter is much more efficient.

First step, locate the image. Then run fdisk -lu on it: 
$ fdisk -ul diskimage
You must set cylinders.
You can do this from the extra functions menu.

Disk diskimage: 0 MB, 0 bytes
15 heads, 17 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x00000000

    Device Boot      Start         End      Blocks   Id  System
diskimage1   *          17      254999      127491+   6  FAT16
This spits out all the information we need to actually mount the loopback device to get this to work. Take the Starting sector number and multiply it by 512. In my case here, it's 17 * 512 = 8704.
This number is needed for losetup to specify where the starting offset is.
Now run losetup: 
$ losetup -o 8704 /dev/loop0 diskimage

$ losetup -a 
/dev/loop/0: [0901]:16793696 (diskimage) offset=8704
This shows that the loopback device is up and at the proper offset. Now just mount loop0 as if it were something like /dev/hda1. We want to mount it Read Only so we don't modify any of the image on accident.
$ mount /dev/loop0 /mnt -oro
$ mount | grep loop0
/dev/loop0 on /mnt type vfat (rw)
That's about it. To get rid of the loop device, umount the partition and run:
losetup -d /dev/loop0


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School: Fall 2007
2007-08-17 09:30:22 posted by Dark-Fx
81484 CS 4121 R01 1 3.0 Programming Languages MWF 09:05 am-09:55 am
82025 CS 4331 R01 1 3.0 Intro to Parallel Programming MWF 11:05 am-11:55 am
81490 CS 4611 R01 1 3.0 Computer Graphics: Foundations MWF 01:05 pm-01:55 pm
81992 PSY 4010 R01 1 3.0 Cognitive Psychology TR 09:35 am-10:50 am
83886 PSY 4120 R01 1 3.0 Human Factors Psychology TR 12:35 pm-01:50 pm
82651 PSY 2200 R01 1 3.0 Behavior Modification T 07:05 pm-09:35 pm


Work M-F, 8-9am, 2-4pm


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disks: New RAID5 array
2007-05-25 08:59:59 posted by Dark-Fx
I gave in and spent the money on 4 new 500G Seagate drives. I already had 2 of them so I figured 6x500G in RAID5 would work great. Right now I have them sitting in my desktop and rsyncing all the data from the mythbox over. After it's all done (going to take a while... ~1.3T of data), I'm going to take the current arrays out of the mythbox and just have this one in it.

The 4x200G SATA array will probably be going in my desktop. I'm planning on selling the 4x300G PATA array to MTU LUG (of which I am president next year) for $75 since we're desperately low on space there too. 
New array:
/dev/md0              2.3T  524G  1.7T  25% /mnt

Old arrays:
/dev/md0              826G  802G   24G  98% /opt/raid0
/dev/md1              551G  534G   17G  98% /opt/raid1

As you can see, I definitely needed the space, because getting rid of the 708G used for mythtv recordings wasn't an option...

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debian: loop-aes
2007-04-23 20:22:26 posted by Dark-Fx
Okay, so we're going to install loop-aes the debian way.

First we need to install some packages:
sudo apt-get install linux-headers-`uname -r` module-assistant loop-aes-source loop-aes-utils

Now, build the module with module assistant:
sudo module-assistant prepare
sudo module-assistant build loop-aes
sudo module-assistant install loop-aes

Now we want to remove the current loop module and insert the new one:
sudo rmmod loop
sudo modprobe loop

My preferred method is to use a small file on an existing partition and mount it seperately:
dd if=/dev/zero of=/volume bs=1k count=1M

This gives us a 1GB file named /volume. I prefer using AES256 so we're going to mount the loopback file here, and write an ext3 partition to it. It will ask you for a password which has to be 20 chars or longer. 
losetup -e AES256 /dev/loop0 /volume
mkfs -t ext3 /dev/loop0

Great. Now we have an encrypted file system. Lets unmount the loop:
losetup -d /dev/loop0

And to mount the file system normally, remember to use the password:
mount volume -o loop=/dev/loop0,encryption=AES256 /mnt/secure/ -t ext3

Now, we want the module to load on bootup. Add this line to /etc/modules: 
loop
And that's it! Piece of cake.


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Utils: Windows Wireless Key Retrieval
2006-11-22 15:23:47 posted by Dark-Fx
I hate the fact that Windows doesn't offer a very simple way to retrieve the keys back out of the wireless system. I found a utility that does it quite well and easily.

WirelessKeyView

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School: Summer 2007
2006-10-26 09:11:52 posted by Dark-Fx
1st half
50401 BA 2300 0A 1 3.0 Accounting Principles I MTWR 09:35 am-10:50 am
51813 FA 4950 02 1 3.0 Story Dev for Role-Playing MTWR 12:35 pm-01:50 pm
50404 BA 3200 R01 1 3.0 IS/IT Management MTWR 02:05 pm-03:20 pm

2nd half
50410 BA 3400 0A 1 3.0 Principles of Finance MTWR 09:35 am-10:50 am
51520 MA 5903 0A 1 3.0 Intro - Scientific Programming MTWR 11:05 am-12:20 pm
50408 BA 2110 0A 1 3.0 Quantitative Problem Solving MTWR 12:35 pm-01:50 pm

Work M-R 8-930, 330-5, Friday 8-5.


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