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I use a 2 Gb Knoppix 6.7.1 LiveUSB as my mainstay OS.
I am not a programmer, but a frequent user.
My uses include internet browsing, e-mail and maintenance of some
personally useful spreadsheets with on-line information.

The CD size of Knoppix with its overlay process suits me very well,
with one exception: that is, when it comes to upgrading some its
larger elements like LibreOfffice or IceWeasel. Re-mastering is the
only really effective way I see to maintain a small end-product. However,
for my particular end uses, re-mastering requires too much additional
resource outlay, and frankly, getting it done exceeds
my short attention span.

I've tried several virtual system aproaches, and am not really
comfortable with any I've tried.

I expect I might be able to pull together an 'in situ' menu-item re-
mastering from available on-line material, but it would require most
of a 16 Gb usb. That would seem to be an absurdly wasteful
use of resources IMO.

Some other distros are going to minimalist base distributions as one
way of getting around my sort of problem. More frequent Knoppix upgrades
would also suffice, but KK has a day job and a family. I suppose he
might delegate some of his distro maintenance tasks if someone
competent were to propose something appropriate.