Viewing D-Link DCS-932L IP camera from Ubuntu

In a word (line) ...

avconv -r 15 -f mjpeg -i http://USERNAME:PASSWORD@IP-ADDRESS/video.cgi -i http://USERNAME:PASSWORD@IP-ADDRESS/audio.cgi -vcodec mpeg4 -f mpegts file:///dev/stdout | vlc file:///dev/stdin

Now, if only the audio didn't crash avconv, we'd be cooking with gas! The silent version is here, and seems stable.

avconv -r 15 -f mjpeg -i http://USERNAME:PASSWORD@IP-ADDRESS/video.cgi -vcodec mpeg4 -f mpegts file:///dev/stdout | vlc file:///dev/stdin

Further Time Machine-esque behaviour

My earlier post on Time Machine-esque backups ( http://lastinfinitetentacle.blogspot.com/2009/06/backups-for-lazy.html )  has some useful links for getting regular differential backups going. However, it can be done more neatly, particularly when it come to Windows, and I've come across a nifty solution here http://www.robgolding.com/blog/2009/01/14/leveraging-vss-and-robocopy-for-robust-backups/

This approach requires the vshadow.exe application, which is its own can of worms. Typically, vshadow ships with a/the Windows SDK - ServerFault has some info ( http://serverfault.com/questions/137126/vss-error-521-when-attempting-backup/137254#137254 ) which suggests getting the Vista era SDK (v6.1, from http://www.microsoft.com/downloads/details.aspx?FamilyID=e6e1c3df-a74f-4207-8586-711ebe331cdc&displaylang=en ). You will only need to install the "Win32 Developer Tools" component; you can ignore everything else.

Using VSS (Volume Shadow Service) will allow an internally-consistent copy to be made of a Windows drive. All I then need to do is port the script here ( http://serverfault.com/questions/27397/sync-lvm-snapshots-to-backup-server/168034#168034 ) to Windows. I could use the script to push the image onto the file server, where it can update SVN repository (a physical backup, for bare metal recovery). Handling the (Windows) shadow drive can be achieved using the Windows-native 'dd' from http://www.gmgsystemsinc.com/fau/ . The same dd tool can be used for an 'easy' recovery. If I get this right, it should be Windows native, and easy to install/maintain.

A separate job will pick out user directories for the Time Machine treatment (more of a logical backup, also on my file server, for basic file recovery) via the mercifully short script I previously linked to, thus: http://blog.interlinked.org/tutorials/rsync_time_machine.html

Technically, I could use Zumastor/ddsnap on the file server to get snapshots/revisions, and I still might...

USB dead device fix

I have a slug (NSLU2) at home, serving out a big USB hard disk. I like my slug. It's small, and it runs Debian, and so long as I remember that it's really small, it runs really well.

It looks like USB drives suffer from lots of issues with dodgey firmware and drivers. Certainly, I haven't escaped them. Every few months I lose the USB drive:
kern.log:

Apr 12 20:32:54 slug kernel: scsi 1:0:0:0: rejecting I/O to dead device

...

This can cause filesystem corruption as well, and is generally "A Bad Thing". Fixing this issue is (for me) a case of remounting the filesystem. I recall once I also had to cycle the power too. Fortunately, I found this page: http://www.mail-archive.com/linux-usb-users@lists.sourceforge.net/msg16510.html which has a very nifty technique for coaxing the USB stack back to life.

I've written a script to pull out the sysfs name of the USB device for a given mount point. At some point I'll add this in to my slug so that it "just works". That just leaves a log scraper to pick up each mount and get the sysfs name, wait for a failure, unmount the dead file system, rebind the USB device, check the file system for damage, and remount the filesystem. Easy!

#!/bin/bash
# get_usb_name.sh 
# e.g.: ./get_usb_name.sh /media/usb2

USB_DEV=$(mount | grep ${1} | cut -f 1 -d ' ' | sed -e 's/[0-9]$//' -e 's(^/dev/((')
USB_ADDR=$(ls -l /sys/block/${USB_DEV}/device | sed -e 's(/host.*$((' -e 's(^.*/((')
if [ -e /sys/bus/usb/drivers/usb-storage/${USB_ADDR} ]
then
echo $USB_ADDR
else
echo "could not verify usb address of ${USB_ADDR} for device ${USB_DEV}" >&2
fi