Wednesday, February 11, 2009

Dear Lazywebs : SSH on low bandwidth connections

Anybody got tips on how to make SSH on low bandwidth / bad connections (eg: 0-4KBps) more bearable?

Disk snapshot backup in Linux


From #myoss @ freenode.net
<kaeru> what do linux people do for full backups?
<kaeru> freebsd there is dump/restore
<kaeru> do people use that for ext3 still or is there a better way?
<sweemeng> kaeru rsync?
<kaeru> I mean disk level snapshots


FreeBSD ufs2, as what we use in Inigo's Gambit, can easily create snapshots of a live filesystem using dump. However, ext2/ext3 used widely in Linux does not have such feature (as far as I know). But for those who want such feature, fear not, there is a feature in LVM called snapshots which more or less provide a similar thing.

Fedora/RHEL/CentOS users might be familiar with the term LVM as the 3 distros uses LVM by default in their default installation partitioning scheme. Some people think LVM by default is a painful thing, but to me, its the opposite (until you need to get it to work with dualboot windows+linux env).

Back to the topic, here's a little guide for those who want to do a full disk image backup using LVM on a live system.

Requirements

- A system that uses LVM as its partitioning scheme (obviously).
- The filesystem must be a LVM managed partition
- Some free unallocated space in the LVM VolumeGroup

This guide will take the assumption the partition you want to backup is `/dev/VolGroup/MyVolume`.

Creating a Snapshot

Creating a snapshot is pretty straightforward.
/usr/sbin/lvcreate -s -L512M -p r -n SnapshotVolume /dev/VolGroup/MyVolume

This will create a readonly snapshot of MyVolume as /dev/VolGroup/SnapshotVolume with 512MB extension.

Backing Up

Once a snapshot is created, you may do anything you wish with `/dev/VolGroup/SnapshotVolume`. eg: use dump or dd the snapshot, or simply mount the snapshot and tar its contents.

Cleaning Up

Once you've done doing your backup, you may remove the snapshot easily using.
/usr/sbin/lvremove /dev/VolGroup/SnapshotVolume


Ok thats it. Have fun.

For more reading, I recommend the LVM-HOWTO at tldp.org

Code Quality Measurement - WTF/m

Saturday, February 07, 2009

Steorn Orbo : Is the revolution near??

I'm quite a fan of science fictions, but when science fictions (might) become reality, it really intrigues me.

Around middle of last year, I went googling for Free Energy Researches simply out of interests. Then I found some news articles about this one company - Steorn about their accidental discovery of a mechanism to generate electricity from magnetic fields, with 200%++ efficiency (read: energy output more than 2 times of energy input).

The CEO seems serious about it, and same goes to his employees. On 2006, they posted a full page advertisement on The Economics, challenging scientists and engineers to come to verify their claim scientifically. On 2007, they wanted to demonstrate a perpetual motion machine in Museum Kinetica, but unfortunately, the device malfunctions (ain't Murphy's Law awesome?). And on 4 February they are back, more convinced than ever, with lots of confidence announced that they will release everything to the public for non-commercial purposes under a modified General Public License (Open Source meet physical science!!!) . They also released 2 devices to test magnetism properties.

This technology, called Orbo, from its functions, appear to break one of the fundamental law of physics , which is the conservation of energy. So, a large number of people are still sceptics until Steorn releases it to public.

For me, I love to keep an open mind in this. Afterall, a few hundreds years ago, everyone believe the earth is flat and at the center of the universe, a few decades ago, everyone believes light is straight (its curved, by gravity), so, it is possible, physics will revolutionized yet again.

Plus, which geek does not want a laptop that does not need charging?. Or a car that does not need refueling?. Or even better, a space travel transportation that does not worry about losing power in the vast nothingness of space?. And, they are clean and produce no direct pollution!.

I'll waits for more announcements from Steorn. Still a bit sceptical until I got access to the free knowledge base and learn about the mechanism. But what's wrong with hoping and letting imagination run wild??. And its going to be interesting when scientist, will need to rethink physics, as one of its fundamental concepts, got broken by a technology company.

First its Free Software, .. and possibly, next is Free Energy .. the future, might come sooner than we think..