New holiday - new self-imposed challenge!
My favourite radio station FXR use Rivendell Audio as part of their play out system, and have recently been donated an [HP TouchSmart 300-1025 PC](http://h20564.www2.hp.com/hpsc/doc/public/display?docId=c01918320 “wikilink”) to use in the public area, which I was asked to 'make work' for audio management duties and general Internet stuff..
Turns out that HP ship the !TouchSmart system with Windows 7 Home Premium, loaded with lots of their own sloooow software (thanks to a not-exactly-rapid hard drive and heavy use of multiple .NET versions), then the owner / donor adds another boatload of cruft like Apple iTunes / Bonjour, ezRecover, several dodgy browser plugins (the usual suspects
- adware, search bars, etc.), several browsers (hello Chrome + Google services) AVG and Norton. The result is a machine that takes 10+ mins to become usable from a cold start and frequently stalls as background tasks hog the I/O bandwidth... not nice.
Fix Attempt 1: Remove the crud, switch to Security Essentials for anti-malware, prune the browsers back to Firefox only and see if it's usable.
Fix Result 1: I bricked it (almost) by uninstalling Bonjour, which seems to completely hose the IP stack. After the uninstall, Windows event log service fails to start and /lots/ of other stuff depends on the event log - broken O/S :( System restore got things back working, then I successfully cleaned out a lot of other junk with help from !SysInternals tools (autoruns is fabulous!), and Process Hacker. Unfortunately it wasn't much more usable in this state, and the Windows version of Rivendell software is unable to play audio, which doesn't make good use of the hardware capabilities. Rethink time.
Fix Attempt 2: Ubuntu 14.04 LTS live CD, re-size NTFS partition(s) and install basic GUI system, then add Rivendell packages. Simples.
Fix Result 2: Ubuntu just worked, almost. Everything except the touch screen was supported out of the box, including the !WiFi card and camera, and as expected it was pretty quick, even after choosing the new Ubuntu GNOME 3 desktop. Some additional rummaging on the 'net produced a working touch screen too :)
Now I hit a problem - the Rivendell Audio version we use @ FXR is officially obsolete (1.7.2 circa 2010) and I have lost the original packages, not that they would install on 14.04 as the dependencies are all wrong..
I can of course query the existing installation(s) for file lists, and collect all the binaries & libraries together. I can also grab the dependency lists, but how to avoid collisions when I need an old library to be used and I have a newer one in 14.04?
My first thought was simply to drop the app and it's libraries (down to libc) in a folder, hack the LD_LIBRARY_PATH and see if stuff worked... kind of, except the app is 32bit, whereas my host O/S was 64bit, and many libraries depended on supporting config files that collided with the host. Hmmn.
Some Googling later, it became apparent that what I needed was a chroot environment, something I tend to avoid as my previous experience with such things has been fragility and continuous maintenance work (I prefer to avoid that!). However, there are now tools available to make stuff easier, in particular the fabulous debootstrap which can build a working chroot version of any Debian or Ubuntu distribution, and schroot which manages all the fragile bind mounts and authentication file copying automatically as you enter/leave the chroot - nice :)
With a bit of assistance I built a chroot environment targetted at 32bit Lucid Lynx (10.04) to match the FXR studio systems, I chose to install the minimum system, which includes apt-get so I can add other components easily. I then worked through the dependencies from the app, and installed appropriate packages to satisfy these. So far so good, but I had no package for the app itself..
Having satisfied the dependencies I then copied the remaining binaries into place from the archive taken from the studio - did it work? Yep :)
Unfortunately Rivendell Audio relies on a number of daemon processes, and other GUI tools to operate, whereas a default chroot expects only transient programs, so some additional work was required, in particular creating a session via schroot to host the daemons, then re-attaching to that session for each transient program. Much learning curve!
Yes the daemon from hell :) However it's mostly useful for normal programs, I just need to get a daemon running in a chroot to use it via ALSA bindings.. sounds easy huh? Well it turns out that other folks have had trouble before, the only reliable approach is to enable network access and use it - other approaches that rely on DBus and shared memory seem to be fragile. So enable network access, limit to localhost and we're done :)
Session on Demand
Last bit - when to run the schroot session and daemons? Given that we depend on pulseaudio and that in turn runs per user login, I chose to have startup scripts for each transient program check for a session and create it.. then on logout it gets torn down. Job done.