Installing BackTrack on USB: mounting dev/loop0 failed

February 21, 2012 in backtrack, bug, fedora, howto, kvm, linux, usb

Recently I wanted to make use of my 16GB usb drive in a sensible way, and I didn’t really need another classic pendrive for moving data. In the end I decided to install BackTrack on it. BackTrack is a general forensic analysis/penetration testing distribution based on Debian. And it’s fairly nice as far as a rescue distribution too.
I could have installed with with UNetbootin, which has direct support for BackTrack, but I wanted something a little more fancy: full disc encryption and persistence of data.
There is a very nice how-to linked from main BackTrack website for doing exactly this sort of thing. But I didn’t want to burn the image first or even reboot. We have virtualization for that today! Right? Right! Or not…
So I downloaded BackTrack KDE/64bit variant iso, checked the md5sum to be correct, and started installation. Silly me thoght that running a KVM VM like this would make it possible to install BackTrack on the usb drive:

$ virt-install -n test -r 1024 --cdrom BT5R1-KDE-64.iso \
--boot cdrom --nonetworks --graphics spice \
--disk path=/dev/sdg

Where BT5R1-KDE-64.iso would be my BackTrack iso image and /dev/sdg would be my USB drive. Sadly this failed with ugly error message after BackTrack started booting:

# (initramfs) mount: mounting dev/loop0 on //filesystem.squashfs failed

After some investigation I found out that BackTrack booted fine if it was the only drive in the system, but failed with the above messages when I tried to attach my USB drive. Never found the reson, but the solution was to make the USB drive use virtio bus like this:

$ virt-install -n test -r 1024 --cdrom BT5R1-KDE-64.iso \
--boot cdrom --nonetworks --graphics spice \
--disk path=/dev/sdg,bus=virtio

After that I just continued according to the how-to with a few differences (such as USB key being seen as /dev/vda). Welcome our encypted overlords.

DevConf 2012 – "How I Have Seen the Future"

February 21, 2012 in conference, devconf, fedora, Red Hat

We’ve had Developer Conference (DevConf) in Brno last weekend and there have been numerous interesting talks and hackfests. You can see the full programme on Fedora wiki.
This year we’ve had a pleasure to welcome a lot of our colleagues from other Red Hat offices around globe. And they in turn had some of the most interesting talks. I spend most of my time at talks dealing with filesystems, storage and other core components, but there were a few not-so-technical talks that sparked my interest.
Bryn Reeves had two talks, one titled “Supporting the Open Source enterprise” and the other “How to lose data and implicate people”. Sadly I had my own lab around fedora-review at the time of the second presentation, but if the first one was any indication the second one must have been great. The talk I’ve seen was dealing mostly with processes and tools our support uses to help customers deal with problems. And examples. Lots of interesting, fun examples of ingenuity of our engineers when dealing with bugs. Yeah, try replicating customer’s setup of few thousand machine grid where the problem occurs. Apparently “git, git, git, git, git, git” is the tool that is saving their lives every day (not surprising).
Other talk that sparked my interest was Lukáš Czerner’s “Btrfs – Design, Implementation and the Current Status”. While Lukáš is not a Btrfs developer, he is a kernel developer familiar with its internals and the talk contained a lof of technical information I haven’t known about before. “The root of the root of the roots” tree must probably be the motto of Btrfs. It looks to me that Btrfs has very powerful abstraction where everything is either a tree or node in a tree, but I guess only time will tell if this abstraction is going to be strong enough for the years to come. I am definitely looking forward to trying Btrfs in a controlled environment (for now).
Another feature that I was drooling over a bit was thin provisioning in LVM that was discussed in a talk given by Edward “Joe” Thornber & Zdeněk Kabeláč. It is a fairly recent feature (first upstream release with support for this was done in January) that allows one to thinly provide LVM volumes. What this means you ask? Well it means you can create 20 GiB volume “pool” that can contain 3 10 GiB thinly provisioned volumes. I.e. these volumes will start small and grow as needed. They will eventually also shrink when space is freed by the underlying filesystem. This of course requires the filesystem to support discard/TRIM commands, but this is not a problem for modern linux filesystems. As I see it thin provisioning teamed with snapshotting will change the way I manage my virtual machines for sure and I can’t wait to try it out.
Many people believe Btrfs will take over role of LVM in following years, but the way I see it Btrfs will simplify use cases that LVM is too complex for, while LVM will keep on improving support for more demanding scenarios. Because let’s be honest, LVM on desktop is just too darn complicated for an ordinary user/administrator.
I’ve been to FOSDEM few weeks back, and I have to say that DevConf was smaller, but no less interesting. There are projects or new features that I haven’t heard about, but caused some “WOW” monents for me. Definitely looking forward to next year! (and you should try to come too)