I wanted to address some of the recent commentary on the GNU Radio Live SDR Environment in one location.
Persistence
This is something supported by the Ubuntu live system when converting our supplied ISO image to a bootable USB drive, typically with a program like Unetbootin. (A direct copy of the ISO image to a USB drive using something like 'dd' does not provide persistence.)
Unfortunately, Unetbootin seems to create boot configuration files for syslinux and Grub that don't enable that persistence, even when it creates the required files to do so. When we make our own USB drives for our training classes, we substitute our own files in place of these after the fact, by copying them into place from:
The grub.cfg file goes into /boot/grub and the syslinux.cfg goes into the root dir of the USB drive *after* unetbootin is completed, overwriting the ones installed by Unetbootin.
(FYI, if you're wondering, the live system boots with syslinux when doing a 'legacy boot' and with grub/EFI when booted via the new EFI system.)
Longer term, we intend to design a livesdr image that is an actual disk image that you can dd into place and that will create a persistence file/partition on first boot. There would be no reason to use a program like Unetbootin.
OS/Kernel Version
All of the "official" GNU Radio livesdr distributions have been based on Ubuntu Linux, and this is unlikely to change anytime soon.
Right now, this is Ubuntu 14.04.3 LTS, as it is the most stable and tested version that is supplied by Canonical. The kernel version does not have support for some newer hardware, or has older, buggy versions of the required hardware drivers.
There is a way (see below) to create a custom version of the Live SDR Environment image based on Ubuntu 15.10, but we are already beginning the design and implementation of the image builder to use the Ubuntu 16.04 LTS alpha, and plan to support that as soon as it is released and we've completed our testing.
Live SDR Environment Installation to Hard Disk
It is often requested to be able to install the Live SDR Environment onto a hard disk for a more permanent development environment solution. This is not something currently supported; the ISO image is explicitly designed to run as a live system and has the Ubuntu Linux installer removed (for space/size reasons.)
The Live SDR Environment is not only a bootable live system with GNU Radio installed, there are 25 additional GNU Radio-based applications and block libraries installed from source code, and numerous tweaks and configuration edits to Ubuntu itself to (ahem) improve performance, security, and privacy. To replicate this on a users' existing Ubuntu installation or to recreate a traditional Ubuntu installation but with all the additions would require a non-trivial amount of work to port the live image build system to a native installer. We might take this up at some point, but unlikely soon.
The ISO image can be booted within a virtual machine, with perhaps some extra work to fine-tune hardware performance in the VM. And of course, one can use the GNU Radio PyBOMBS installer to install GNU Radio and all of the extra software on the live image on whatever platforms that supports.
Custom ISO Images/Live SDR Environment Builder
The generation of the live image ISO file is completely modular and automated. It is a branch of the Ubuntu Remaster system from Corgan Labs, which is a general purpose live image customization tool:
You can clone this repository and build your own custom live images as variations on the GNU Radio one, adding or removing software components as desired. The base system (prior to the GNU Radio additions) also supports several privacy enhancing options, like fully encrypted ISO images, transparent Tor proxying, and removal of Ubuntu "features" like the Amazon integration and online search scopes.
Ubuntu 15.10 kernel support is possible, though it is relatively untested and only enabled when turning on the experimental features.
One of the areas being worked right now is to be able to choose other window managers like Xfce or KDE as an alternative to Unity.
The workstation storage and CPU, and bandwidth requirements to build your own ISO image from scratch are heavy, however--this is not recommended for end users so much as people who want to create their own derivative distributions. And, to completely honest, it is not very well documented.
Hopefully this clarifies some recent issues people have reported, and I welcome questions/suggestions/testers/pull requests.
-Johnathan