OpenVPN on the DNS-323

There are times I want to grab files from my trusty DNS-323 when not at home. Recently I found time to try opening up access to it using OpenVPN.  This post shows the steps... and it really is simple to setup. I tested the process with Linpus, Fedora 12 and Windows XP as a client, and all went smoothly.

Transcoding MJPEG to Xvid

Videos from the Canon IXUS 80 weren't playing properly for me either with VLC (Linux or XP) or Media Player.. so I thought I'd try transcoding them. It worked nicely.
See my earlier posts for the transcode install process.

Input file -
[user@aspireone ~]$ tcprobe -i MVI_2282.avi
[tcprobe] RIFF data, AVI video
[avilib] V: 30.000 fps, codec=MJPG, frames=7607, width=640, height=480
[avilib] A: 44100 Hz, format=0x01, bits=16, channels=1, bitrate=705 kbps,
[avilib] 254 chunks, 22364580 bytes, CBR
[tcprobe] summary for MVI_2282.avi, (*) = not default, 0 = not detected
import frame size: -g 640x480 [720x576] (*)
frame rate: -f 30.000 [25.000] frc=0 (*)
audio track: -a 0 [0] -e 44100,16,1 [48000,16,2] -n 0x1 [0x2000] (*)
bitrate=705 kbps
length: 7607 frames, frame_time=33 msec, duration=0:04:13.564

Transcode to Xvid -
transcode -i MVI_2282.avi -y xvid4 -o MVI_2282.xvid

Output file -
[user@aspireone ~]$ tcprobe -i MVI_2282.xvid
[tcprobe] RIFF data, AVI video
[avilib] V: 29.970 fps, codec=XVID, frames=7606, width=640, height=480
[avilib] A: 44100 Hz, format=0x55, bits=16, channels=1, bitrate=128 kbps,
[avilib] 7606 chunks, 4055761 bytes, CBR
[tcprobe] summary for MVI_2282.xvid, (*) = not default, 0 = not detected
import frame size: -g 640x480 [720x576] (*)
frame rate: -f 29.970 [25.000] frc=4 (*)
audio track: -a 0 [0] -e 44100,16,1 [48000,16,2] -n 0x55 [0x2000] (*)
bitrate=128 kbps
length: 7606 frames, frame_time=33 msec, duration=0:04:13.786

The other benefit -
[user@aspireone ~]$ du -h MVI_2282.*
435M MVI_2282.avi
59M MVI_2282.xvid

Tomcat on DNS-323

Given my lack of success with bridging for VirtualBox, I thought I'd try starting Tomcat on the DNS-323.

Starting with hope provided by this post.

The process was remarkably easy. Follow this post to get optware setup.
Then install the jamvm optware package.
Next, follow this post to install Tomcat.

It's a bit of a memory hog,
Mem: 60260K used, 1644K free, 0K shrd, 11220K buff, 8916K cached
CPU: 1% usr 0% sys 0% nice 97% idle 0% io 0% irq 0% softirq
Load average: 0.03 0.06 0.18
PID PPID USER STAT VSZ %MEM %CPU COMMAND
30766 30688 root S 40204 65% 1% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30687 30686 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30767 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30835 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30824 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30836 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30690 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30691 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30689 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30768 30688 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak
30688 30687 root S 40204 65% 0% jamvm -classpath /opt/share/classpath/glibj.zip:/opt/jak

and painfully slow -
INFO: Server startup in 151671 ms

but it seems to be reasonably functional... although trying to run a database as well on the DNS-323 would be a stretch.

VirtualBox Bridged Mode on Linpus

I wanted to run TurnKey Tomcat in VirtualBox, and use bridged network mode to make the tomcat available on my LAN. Easy I thought...

The basics of setting preparing the host Linux environment I found this post.
However, the Linpus kernel doesn't have
- TUN/TAP support built in the kernel... so I turned to this post.
- Bridge support... so it was time to build my own kernel, for which I turned to this post.

I then discovered that Linpus has a custom build of Grub, that doesn't show a menu on boot... which was something of a problem, as my kernel, built with 'CONFIG_BRIGE=y" did not work properly - the mouse and keyboard didn't seem to work.

I hope to replace the Linpus grub with a more standard variety... but this I'll save for another post. I want to make sure I have a safe procedure for restoring the original version first.

On a side issue, I tried using
- Damn Small Linux (DSL) for recovery - but it hung whilst booting.
- RIPLinux - at first this didn't seem to work either... until I found that by first running it's hardware detection tool, and then running grub, it worked nicely. Strange incompatibility with the Aspire One I suspect.

For my kernel second build, I tried with bridge as a module, CONFIG_BRIGE=y. This worked nicely.

I then hit this error - VERR_SUPDRV_COMPONENT_NOT_FOUND which is easily resolved by modprobing, see this post.

Then, to my horror, I found that Linux bridging doesn't work on WIFI - see this post.

If anyone tries this procedure, and gets it to work, perhaps against a regular Ethernet port, I'd like to hear your experiences.

Snapshots in VirtualBox

Firstly, I want to give credit to this thread - as it steered me onto the right path.

The way snapshots and virtual media (hard disks) work in VirtualBox is clearly not entirely obvious to the newbie, myself included. If you don't understand it, it looks plain buggy... however once you've understood it... there is reason in the madness - and more importantly it works!

In VirtualBox there are 3 types (or modes) of virtual hard disk images, Normal, Immutable and Write-through. These are fairly well explained in the manual - I highly recommend reading at least that section of the manual, as it also helps make sense of snapshots.

I'll discuss only the 'Normal' image type here. This is the default type set, when you create a new machine and hard disk. You start up your guest OS, and everything works nicely. You try powering off the machine, saving the state, everything works as you'd expect.

Then you see the 'Take snapshot' option, and try it. Now, you need to understand how they work - whether you know it or not :)

The snapshot stores the machine state, just like the 'current state' you've used up until now. It also contains a differential image of the hard disk. Ie. from now on, the (normal) hard disk image file (eg. xp.vdi) that was previously being updated, is no longer updated. Instead, when your guest OS writes to disk, it writes into the differential image.

If you create another snapshot, a new differential image is created, so now, the current content of the hard disk is stored across 3 files, the original, and the two snapshots. This of course gives the possibility to go back to an exact, earlier copy of the entire system (including hard disk).

So what's the problem?

Snapshot files, including the differential hard disk image aren't particularly portable. So whilst you can easily move your original hard disk to different machines, moving the updates in your differential files is difficult. Unless you run on basically the same host machine, with the same vbox version you can restore the changes from your differential images.

Or can you?

The solution is to discard your snapshots!

Sounds dangerous? Well, not quite as dangerous as it seems. When you discard a snapshot, it merges the differential image into it's parent image.

So, if you have snapshots like this -

- Snapshot 1
  - Snapshot 2
     - Current State

And discard 'Snapshot 2', the differential image changes will be merged back into Snapshot 1, leaving -

- Snapshot 1
   - Current State

Then discarding 'Snapshot 1', will merge back into your original hard disk image 'xp.vdi'... leaving no snapshots, but also a portable hard disk image.

I recommend experimenting by taking a snapshot, then create some files in the guest OS, and then create another snapshot. Then discard away, and see that the files survive.

Commodore 64 on the iPhone

Well this is totally off topic, but it has two strong connections to my past. The C64 which I spent countless hours programming and hacking in my youth, and and old friend, whose personal company developed the product.

So go ahead and take a look -
c64iphone
Full Commodore 64 emulator rejected from App Store

Tiresome

But just because they bug me so much, here's the latest spammer from my www logs -

118.168.136.169 - - [29/Apr/2009:13:54:46 +0200] "CONNECT maila.burst.idv.tw:25 HTTP/1.0" 501 357 "-" "-"