Akom's Tech Ruminations

Upgrading Dell laptop memory and the blinking CAPS LOCK led

nospam@example.com (Admin) — Wed, 18 Jan 2012 10:05:56 -0500

Apparently if you have the power-on self-tests set to "Minimal" or "Fast" or anything besides the "Let's check everything for 5 minutes every time the machine boots", you'll have a brick with a blinking CAPS lock instead of a laptop once you upgrade memory.

The only way I found to fix this (other than clearing the BIOS) was to put the old memory back in, go into BIOS, and enable thorough self-test. With that on, the laptop notices the memory size change and does not freak out - merely tells you about it. Once you're done you can disable the self-tests.

(I experienced this on a Dell Precision M4400, but googling seems to indicate that this affects the Inspiron and Latitude lines as well, probably others).

Getting Meetme to work in Asterisk 1.6 on Ubuntu Lucid

nospam@example.com (Admin) — Tue, 15 Nov 2011 11:57:19 -0500

I'm assuming that you are attempting to use the Meetme() application and getting an error like this:

WARNING[10695]: app_meetme.c:1097 build_conf: Unable to open pseudo device

It's rather simple:

$ apt-get install dahdi dahdi-dkms dahdi-linux #I think dahdi may be enough
$ echo dahdi_dummy >> /etc/modules
$ modprobe dadhi_dummy
$ ls -l /dev/dahdi/pseudo
crw-rw---- 1 root dialout 196, 255 2011-11-15 11:26 /dev/dahdi/pseudo
$ id asterisk
(Should include 'dialout' group)

Yay! Apparently in Asterisk 1.6 the timing source for the Meetme application is no longer ztdummy (fortunately I was unable to use m-a to compile zaptel) but rather relies on DAHDI, not only for timing but for conference mixing - see http://www.russellbryant.net/blog/2008/06/16/asterisk-16-now-with-a-new-timing-api/

Asterisk CDR records 's' for DST when Dialing from Macros

nospam@example.com (Admin) — Fri, 22 Jul 2011 12:11:09 -0400

At some point in the Asterisk 1.6 evolution the CDR records stopped being useful in my setup for outgoing calls - instead of a nice number (eg 18005551212) in the dst field of the record, I now have an s. I log my CDR to MySQL and I do use a macro (with AEL) to dialout. My macro is even called dialout.

According to this bug, this is a known issue and no immediate fix is expected. Not wanting to rewrite the CDR UI to use yet another column, I figured that I can fix this with a MySQL trigger, so here is one possible workaround.
Continue reading "Asterisk CDR records 's' for DST when Dialing from Macros"

Figuring out the card number of a cheap SAA7130 capture card

nospam@example.com (Admin) — Sun, 19 Jun 2011 09:26:27 -0400

So you bought yourself a cheap Philips SAA7130 (or SAA713X or SAA7134) capture card to record motion, you plugged it in and you are getting a black or grey screen. Looking in dmesg you see the famous saa7134[0]: Huh, no eeprom present (err=-5)? And

saa7134:  Congratulations!  Your TV card vendor saved a few
saa7134:  cents for a eeprom, thus your pci board has no
saa7134:  subsystem ID and I can't identify it automatically
saa7134: I feel better now.  Ok, here are the good news:
saa7134: You can use the card= insmod option to specify
saa7134: which board do you have.  The list:

What do you do? How do you try 175 card numbers and figure out which one works? Write a script!
Continue reading "Figuring out the card number of a cheap SAA7130 capture card"

Migrating one Gmail account to another

nospam@example.com (Admin) — Fri, 13 May 2011 14:50:57 -0400

I have a setup where a Google Apps Premier account is used for the active employees, but when they quit I want to archive all their mail but free up a paid user account for the next employee. We archive mail in a different domain, also on google apps - a standard edition, free. For a while now I've gone through a variety of ways of copying the mailboxes from one place to the other, and each approach was either partial, unreliable, or too time-consuming.

So I think I've finally settled on a viable approach that is neither.
Continue reading "Migrating one Gmail account to another"

Setting the date/time on the Mini Keychain Spy Camcorder

nospam@example.com (Admin) — Mon, 25 Apr 2011 21:57:05 -0400

Keychain Camcorder

The instructions that come with this little gadget are priceless in their verbatim Chinese glory, but are not helpful in their vague "Leave the details as an exercise for the reader" approach.

Here are the exact detailed steps to actually set the clock
Continue reading "Setting the date/time on the Mini Keychain Spy Camcorder"

Backing up cPanel without hitting logout

nospam@example.com (Admin) — Thu, 21 Apr 2011 19:26:57 -0400

cPanel based hosting presents some challenges for automatic backups - there isn't an automatic way of creating local backups or any standard way of triggering their creation remotely. Numerous scripts exist yet none were quite the solution I was looking for - I am primarily interested in the databases and mail forwarders, though files wouldn't hurt either. Moreover - you can do this in a single line!

My Goal therefore is: Create and retrieve backups nightly. I don't want cPanel to push files to my off-site box, I'd rather initiate everything remotely and not have to open up access to some other system. cPanel does permit one to do this using a browser, hence it can be scripted. Really, scripting isn't even necessary - wget is all that is required! That said, I had a very hard time convincing wget not to visit the logout link on each page - once you log out, you're not getting anywhere anymore. So here is how I did it.
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MySQL replication dies with fatal error 1236: Client requested master to start replication from impossible position

nospam@example.com (Admin) — Fri, 04 Feb 2011 10:33:30 -0500

This time, my master-master setup stopped replicating with no explanation at all - running START SLAVE yielded no warnings or errors. Inspecting the log yielded the aforementioned error (on Ubuntu, mysql logs to /var/log/syslog by default):


[ERROR] Error reading packet from server: Client requested master to start replication from impossible position (
server_errno=1236)
[ERROR] Got fatal error 1236: 'Client requested master to start replication from impossible position' from master
when reading data from binary log
[4654]: 110204 10:09:20 [Note] Slave I/O thread exiting, read up to log 'mysqld-bin.000742', position 4274

So at first I thought this was a weird bug or a stunnel issue, but looking at 'mysqld-bin.000742' on the master it turns out that it's only 3980 bytes - position 4274 is indeed impossible. But how did it get this way?
Continue reading "MySQL replication dies with fatal error 1236: Client requested master to start replication from impossible position"

The Eclipse, PDT and Smarty dance

nospam@example.com (Admin) — Mon, 24 Jan 2011 16:17:56 -0500

Eclipse is a great developer tool, and I use mine for Java, PHP, and C++. It actually does all of the above really well, but when it comes to Smarty template Syntax Highlighting, it's a tale of much suffering. I honestly am not even asking for any Smarty auto-completion - just pretty colors that tell me when I'm fat-fingering the syntax.

Fortunately there is a solution that appears to work, and here is the currently valid step-by-step
Continue reading "The Eclipse, PDT and Smarty dance"

Simple flat file site search in PHP/Smarty

nospam@example.com (Admin) — Wed, 19 Jan 2011 17:14:36 -0500

Sometimes using a real search implementation (Lucene, Sphinx) is just too much. The particular site I was working on is something like 30 pages, it's maintained as flat files (Smarty templates, but it's basically HTML on disk), and it really, really should not require megabytes of code and cron jobs to be able to search it!

That said, this is a simple search solution - it makes a lot of assumptions:
Continue reading "Simple flat file site search in PHP/Smarty"

Predictable ALSA numbering of USB sound cards

nospam@example.com (Admin) — Wed, 12 Jan 2011 10:07:48 -0500

I have 3 rather cute Monoprice usb sound cards for use by mmpd (client I wrote for multiple mpd instances). The great thing about them is that for $9 you can just keep adding zones to your music systems. The bad news is, UDEV will reorder sound cards on boot as it pleases.

Zones changing would be survivable in itself (reboots are rare), but I also have a webcam and an onboard sound card that I don't use - so sometimes the numbers I've configured mpd to use aren't even valid sound cards! On to the continuing search for a working solution
Continue reading "Predictable ALSA numbering of USB sound cards"

Fixing digitemp with LinkUSB on kernels after 2.6.32-24

nospam@example.com (Admin) — Tue, 11 Jan 2011 16:28:22 -0500

As many people have discovered, kernels after 2.6.32-24 changed the USB-RS232 serial driver to not set hardware flow control (RTS/DTS) flags. No doubt there was a good reason. Unfortunately, digitemp and owfs don't enable it either, also probably for a good reason - at least when applied to older devices. What this means is that now when you try to use a LinkUSB (and probably other DS9097U type hardware behind USB to Serial converters), digitemp and owfs no longer work.

Let's apply a time-tested hackish approach.
Continue reading "Fixing digitemp with LinkUSB on kernels after 2.6.32-24"

How to take down your pfSense firewall with one checkbox

nospam@example.com (Admin) — Sat, 01 Jan 2011 16:07:12 -0500

Simple: create a Traffic Shaper queue but forget to choose a queue parent.

Your firewall will not pass any packets across, and you'll have no idea what hit you.

Troubleshooting car heat issues or why stop-leak is a bad idea

nospam@example.com (Admin) — Sat, 30 Oct 2010 13:16:44 -0400

I got my truck exactly a year ago. It came complete with stop-leak (the red brick-colored pellets) in the system. I immediately flushed out all coolant and stop-leak (must have run 100 gallons through the system with a back-flush kit), but I guess that wasn't enough, as I suddenly found myself without any heat whatsoever. Now I am not that into heat, but the idea of a sheet of ice on the windshield with no recourse just doesn't sound like fun.

Since I had to figure out what the issue was step-by-step, I figured I'd write the process down for posterity (read: me, next time). So here it is...
Continue reading "Troubleshooting car heat issues or why stop-leak is a bad idea"

Asterisk and obfuscated SIP port redirection - calls drop after 20 seconds

nospam@example.com (Admin) — Tue, 05 Oct 2010 11:31:14 -0400

One of my asterisk setups got attacked recently by a brute force script kiddie. The attack is simple:

Try sequential sip usernames from 1 to 10000, hoping that the admin chose a numeric username scheme
If asterisk returns anything but a 401, then perhaps this is a real account, add it to the list
If anything is on the list of "possibles", then brute force their passwords

Why this works:

Asterisk has no delay for failed logins, so a brute force attack is viable, hundreds of attempts per second are possible. Not sure what can be done about this
The admin didn't set alwaysauthreject = yes in sip.conf. It's off by default, why??? With this enabled, there is no way to tell if a username is valid from the reject response

To deal with this:
Continue reading "Asterisk and obfuscated SIP port redirection - calls drop after 20 seconds"