What to do about that crappy dm9601 you got on eBay

Note that the title is past tense. Don’t buy these dreadful things intentionally!

They’re typically advertised as USB 2.0 10/100 Ethernet dongles. The photo will suggest that there’s a Realtek chip inside. It’s all a lie. They’re actually USB 1.1 and 10mbps half duplex. Speeds top out at under 8mbps (bits, not bytes). Pretty much useless for anything these days.

But let’s say you bought one. Worse yet, you bought one a few years ago, forgot how bad it was and bought another one.

Maybe your old one was hanging off a Raspberry Pi Zero running piCorePlayer and was plenty fast for local streaming even FLAC audio. Of course your other players have better network dongles (even the one that was salvaged from an ancient Tivo that was gathering dust in your part pile but I digress).

So you get the bright idea to salvage this useless dongle you just bought and swap it for one of the better dongles being “wasted” on one of your other players. It frees up the better dongle to use for the current project and the piCorePlayer will be just fine… or so you’d think.

You make the swap and suddenly both piCorePlayers with the dm9601 stop working! Swap back to the good dongle, reboot both, all good. Swap back to the dm9601 and both players go crazy. The music server shows both players winking on and off.

No… it can’t be. Do both dongles, purchased years apart, have the same MAC address? Your router seems to think so. You Google the MAC address (00:e0:4c:53:44:58) and start finding lots of confused and unhappy dm9601 owners. Pretty much all the threads ended in abuse (you idiot, just return it!) and frustration.

Ok. Yeah, that hypothetical sucker was me. Both times. I started searching for a solution and finally found this thread that seemed to reach a workable solution: https://forums.raspberrypi.com/viewtopic.php?t=167249.

I tried using ip (or in piCorePlayer’s case ifconfig) to change the MAC address. It worked but the change was only semi-persistent. It seems to generally survive reboots but unsurprisingly gets reverted on power off.

I then tried adding ifconfig eth0 hw ether "00:11:22:33:44:55"; killall -USR1 udhcpc to various places in the startup script but it wasn’t working consistently. Too early and it wouldn’t take effect. Too late and the player would come up with the default MAC and then change later leaving behind phantom players in the media server.

The working solution was to add the command to the udev rules to change the IP right as the dongle comes up – I didn’t even need to poke udhcpc afterward.
I created a file called 77-mac-fix.rules in /etc/udev/rules.d with the following:

ACTION=="add", SUBSYSTEM=="net", DEVPATH=="/devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0", ATTR{address}=="00:e0:4c:53:44:58", RUN+="/sbin/ifconfig eth0 hw ether 00:11:22:33:44:55"

For piCorePlayer I also had to add the file path etc/udev/rules.d/77-mac-fix.rules to /opt/.filetool.lst and run pcp backup to make the change permanent.

A word about that DEVPATH. You’ll need to find one for your specific dongle. Look in /sys/class/net/ to find the path for your dongle:

$ ls -l /sys/class/net/
total 0
lrwxrwxrwx 1 root root 0 May 30 11:45 eth0 -> ../../devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0/
lrwxrwxrwx 1 root root 0 Dec 31 1969 lo -> ../../devices/virtual/net/lo/

So for my device (eth0) the DEVPATH was /devices/platform/soc/20980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/net/eth0. My two dongles were slightly different so yours probably will be too.

I hardcoded different MAC addresses for each of my players and now they’re both working as expected.

But really. These things never should have been produced in the first place. Don’t buy one.

New life for old toys

I’ve accumulated a number of old PCs, laptops, and even a couple of servers over the years. With the recent chip shortages and supply chain problems I’ve taken to finding new applications for them.

Compatibility is surprisingly good. The x86-64 platform has been around for a long time. One problem I’ve hit recently is that UEFI has been around long enough so older BIOS’es can no longer boot some software which is distributed as disk images.

I ran into this with the HassIO “appliance” version of HomeAssistant. I was looking to set it up on an old ThinkPad T500 which didn’t have UEFI support.

But first a little digression.

Playing around with old hardware meant I was going to be trying all kinds of old installation disks. Either burning CD/DVDs or struggling with things like Rufus, UNetbootin (which I think is pronounced you-not-booting), etc. It gets old pretty fast.

Until I found a GPL-licensed tool called Ventoy.

Ventoy is a really cool tool. You install it on a flash drive with a simple command and from that point forward, all you have to do to boot an img or iso file is to copy it to the flash drive. You have store many images on the flash drive and you get a menu from which you can select which image to boot.

So far, I’ve used it successfully with Ubuntu, ParrotOS, Debian, GParted, and a few of the Puppy Linux images. The only one that gave me trouble so far is TinyCore Linux which seemed to have some UEFI issue – I’m not interested enough right now to troubleshoot it.

Anyway, this one’s a keeper. Check it out at https://www.ventoy.net.

I’ll have to get back to the UEFI boot story later. In the meantime, here are instructions for HassIO if you need them: https://community.home-assistant.io/t/install-ha-on-old-laptop-without-uefi/407443/20.

Install Flirc software on Fedora (and other RPM based distros?)

The Flirc Media Center Companion is a neat little USB device that lets you use any IR remote control with your Raspberry Pi or Android stick. The software you need to set it up is available for Linux but they only maintain the Debian package. There’s an old RPM available but I had problems installing it.

Here’s what I did to create a working (and current) RPM version:

  1. Download the latest DEB file that matches your architecture here: http://apt.flirc.tv/arch. For example, for 64 bit at this time that’s http://apt.flirc.tv/arch/x86_64/binary/flirc_1.3.6-1_amd64.deb.
  2. Convert it to an RPM with alien: sudo alien -r flirc_1.3.6-1_amd64.deb
  3. Remove the unnecessary and conflicting entries: rpmrebuild -p –change-spec-files=”grep -i flirc” flirc-1.3.6-2.x86_64.rpm

That command will create a new RPM that should install cleanly and it all seems to work fine for me. I’m on Fedora 21 64-bit.

Lazy Admin’s Guide To Changing Mongo Oplog Size

Have you read Mongo’s official guide to changing the size of your oplog http://docs.mongodb.org/manual/tutorial/change-oplog-size/ and found it a bit intimidating? Are you resizing it because you already have replication problems anyway? Might as well rebuild your secondary and increase the oplog size in one shot. It’s basically the same as the procedure outlined here: http://docs.mongodb.org/manual/tutorial/resync-replica-set-member/#automatically-sync-a-member.

1. Set the oplog size in /etc/mongodb.conf. Just add this line (the size is in MB):
oplogSize = 102400

2. Stop your server with:
db.shutdownServer()

3. Empty the data directory – the one set by dbPath. You can remove all the files but it’s probably a better idea to move them to a backup directory in case anything goes wrong.

4. Start your server.

That’s it. The server will find the empty data directory, initialize it using the new oplog size, rejoin the replica set and perform a complete initial sync.

Now, you wouldn’t want to do this on a huge production database but if your database isn’t too large, it’ll save you a bit of reading.

More consistent iteration times

We were doing some quick and dirty load testing the other day, using a simple shell script to load messages into a queue in batches. The code looked something like:

while something ;do
echo Sending messages $(date)
send-messages
some-other-stuff
sleep 5
done

It seemed to be working but every few iterations, the time would skip by 6 seconds instead of 5. Obviously, the time it took to send the messages and do some other stuff was adding up. Since we’re in quick and dirty mode anyway, my first instinct was to run the send-messages asynchronously (the other stuff was printing log output and had to run in sequence), so we just added an & to the end of the send-messages line and the number of skips dropped by about a third.

This was an improvement but we were still skipping pretty often and we realized we could do even better.

Rather than using sleep to add a delay, we realized we could use it to act more like a timer. We started the sleep in the background at the top of the loop body and called wait once the body of the loop was done and ready to pause for the remaining time. It was a simple change:

while something ;do
sleep 5 &
slp=$!
echo Sending messages $(date)
send-messages
some-other-stuff
wait $slp
done

This kept each loop iteration really close to the 5 second goal. We might still see some drift over time but it was good enough for our purposes.

WebSphere Jython scripting, add the script directory to the import path

If you’re running a script with wsadmin and it tries to import other modules that live in the same directory, you’ll discover another difference between Python and wsadmin. Python will always look for modules in the path that the script was run from. wsadmin won’t. This is kind of annoying if you have a few local import files. Sure, you can always add a directory to the import path via the command line but who ever remembers to do that (and who remembers the syntax)? Since we already have the script path (from fix5), we might as well add it to the import path.

if mainfile:
    mainpath = os.path.dirname(mainfile)
    if mainpath:
        sys.path[:0] = [ os.path.abspath(mainpath) ]

See fix5 for the computation of mainfile. Better yet, download the whole collection from here.

Running the latest Bing on “not supported” devices

There’s a new version of Bing available here that supports speech input and turn-by-turn spoken directions. It even seems to have traffic avoidance. I’ve barely had a chance to play with it yet but I wanted to pass along a fix for the “Your device has been identified as not supported.” error you’ll get on any but the very latest phones.

Go to the Bing install directory, mine was “Storage CardProgram FilesBing”, and edit the file “Bing.config”. Find the entry “UseAppServerUpdates”. Change the value from “True” to “False”. Save the file.

That should do it. The application runs now and I don’t get the error anymore.

This was tested on an HTC Kaiser running some 6.5 ROM.

WebSphere Jython scripting, sys.argv[0] and __file__

Today’s problem is that wsadmin sets up sys.argv differently from normal Python (or Jython).  In Python, sys.argv[0] is the name of the script you invoked.  What you’d normally think of as the command line arguments start at index 1.  For whatever reason, wsadmin doesn’t pass the script name.  The arguments are passed in starting at sys.argv[0].  This can be a nuisance if you have a script that you want to run both in wsadmin and Python.  It’s also just one more difference to trip over.

I should give credit to this post for reminding me that this needs fixing and also for pointing out that the full command line is available in the environment.  Thanks!

My code for this is a little clumsy.  Basically, we scan the command line we get from IBM_JAVA_COMMAND_LINE for the -f option.  We  don’t want to pick up just any -f that might be passed as an argument to the script, easy to avoid by stripping off anything after a -- argument.  We also don’t want to pick up a -f that might appear among all the environment data that wsadmin prepends to the command line (unlikely as that might be), so we look for the last -f after removing any -- that might be present.  Even so, if the script name contains a space, we’re not going to get the whole name.  Such is life.

topframe = sys._getframe()
up1frame = topframe.f_back
while topframe.f_back:
    topframe = topframe.f_back

cmdline = os.environ.get('IBM_JAVA_COMMAND_LINE')
if up1frame == topframe and cmdline and not topframe.f_globals.get('__file__'):
    beg = 0
    end = len(cmdline)
    # Throw away everything after the '--', if present.
    dashdash = cmdline.find('--', beg, end)
    if dashdash >= 0:
        end = dashdash
    # If we can't find a filename, just use a "-"
    mainfile = '-'
    dashf = cmdline.rfind(' -f ', beg, end)
    if dashf:
        # Grab everything from after the "-f" to the following space.
        beg = dashf + 4
        space = cmdline.find(' ', beg, end)
        if space >= 0:
            end = space
        mainfile = cmdline[beg:end]
    sys.argv[:0] = [ mainfile ]
    topframe.f_globals['__file__'] = mainfile

By the way, I threw in a little bonus.  In wsadmin, __file__ isn’t normally set for the top-level script.  That last line will set it.

As usual, the complete listing for this evolving bundle of fixes is ibmfixes.py.

Update 4/16/2010: I decided this fix should only be applied if imported directly from the top level. This will keep it from potentially breaking existing main programs that don’t know about it.

WebSphere Jython scripting, __name__ == ‘__main__’

Here’s another small fix.  In Python and even in Jython, the __name__ of the topmost script is ‘__main__’.  This is mostly used in the idiom:

if __name__ == "__main__":
    main()

In wsadmin, __name is set to ‘main’. Rather than put the clumsy:

if __name__ == "__main__" or __name__ == "main":
    main()

… in every script, let’s solve this once and for all:

topframe = sys._getframe()
up1frame = topframe.f_back
while topframe.f_back:
    topframe = topframe.f_back
try:
    if up1frame == topframe and topframe.f_locals['__name__'] == 'main':
        topframe.f_locals['__name__'] = '__main__'
except:
    pass

As usual, the current collection is at http://dbrand666.wordpress.com/ibmfixes-py

Update 4/16/2010: I decided this fix should only be applied if imported directly from the top level. This will keep it from potentially breaking existing main programs that don’t know about it.