Typically, a DVD cloop Knoppix image contains about 10 GB worth of programs and data, yielding an average ca 2.4x compression. For extra installs, still about 2x compression can be expected, and when much of it comes from upgrading, about 2GB used space on the persistent store may still result in an acceptable size of the new compressed image upon remastering.
If not much of it is Java (or mono) tools or packages, that is. Installs that consists mainly of jar ( war) files or other compressed formats will not compress that much, if at all. Integrating them in a compressed image doesn't help much in any way, and they are best left as is on the persistent store. For simple remastering, they must then either be hidden or temporarily removed. Linking to another permanent location is also an alternative, just remove the links before remastering.
This applies, among other things, to Eclipse derivatives, like the SpringSource tools for Groovy/Grails, application servers like jBoss server, GlassFish and Java Enterprise Edition. Such packages easily add to 1-2.5 GB, but they may still fit comfortably on a 4GB persistent store. And if they don't, either the store space can be increased, or several loop images may be used. Both approaches work just fine, what I think is less useful, is to create another cloop overlay for them.
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