Software Installation Using Disk Images By Irena Lanc

Software Installation Using Disk Images By: Irena Lanc and Peter Sempolinski

Software Installation � Conventional methods of software installation involve: � Downloading the package � Unpacking � Compiling � Managing path and environment variables � This leads to package files being strewn in directories across disk. � How can this system be made more efficient?

Our Idea � Create a disk image of the software package, and mount it as a loop device. Virtual File System Image un-installation script Imageinstallation script Unionfs X X Loop-mounted Device Loop- mounted Device Underlying ext 2 filesystem

Basic Working Prototype

Complications � Number of loop devices hard-limited in kernel � Possible to ask for more devices at boot time. However, this greatly slows down the boot sequence when number of devices > 4000. � System accommodates up to 1000 devices comfortably. � A typical system could have between 1000 -2000 software packages Loop Devices vs Boot Time 400 Boot time (s) 350 300 250 200 150 100 50 0 0 500 1000 1500 2000 2500 3000 Number of Loop Devices 3500 4000 4500

Complications � Dependencies � Images created using files from debian packages, but since we’re re-packaging, dependencies not automatically fetched. � Further tools needed to manage dependencies. � Unionfs � Demands careful coordination of merges by the script. � As yet untested in scalability when merging hundreds of packages.

Road Ahead � 1. Add more scripts to manage dependencies, and generally make system easier to use. � 2. Create a test bed to obtain metrics such as program install time, memory/processor usage, and scalability. � 3. Kernel hacking � To get more out of Unionfs/loopback devices, certain aspects could be modified to provide more flexibility and better performance