This is the tutorial for cowbuilder. See also [:qemubuilder: qemubuilder].
Create the base image:
sudo cowbuilder --create
And a new and shiny build image is created in /var/cache/pbuilder/base.cow/
Every day usage
Update the base image
sudo cowbuilder --update
Build a package:
sudo cowbuilder --build somepackage.dsc
Slow copying and removing of the COW directory
What cowbuilder does is:
cp -al /var/cache/pbuilder/base.cow /tmp/new rm -rf /tmp/new
Of course cowbuilder uses a different location than /tmp/new. You need to optimize those 2 commands on your computer. So try to run them by hand and possibly try a different filesystem and be sure it's not very full. For details, see our [:cowbuilder_benchmark: benchmarks].