Update I just installed it to confirm but dd is installed with the default installation of DSL. The following only applies if you've somehow removed it (if that is the case then you may have a lot of other important stuff missing too, you may be better off starting fresh too because this could be really difficult to fix manually.
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Open a terminal. At the prompt, type the following:
wget http://distro.ibiblio.org/pub/linux/distributions/damnsmall/mydsl/gnu-utils.dsl This will download the gnu-utils.dsl file onto /home/dsl. If this did not work, your problem is probably your internet connection. Check if the file was downloaded properly by confirming that its size is around 1.2 MB ( ls -lh ~/gnu-utils.dsl ).
Then at the prompt, type the following:
mydsl-load gnu-utils.dsl This will load the extension. Check this by executing the following command:
dd --help If everything is working you can delete ~/gnu-utils.dsl.
A full listing of programs which can be installed this way is on the DSL site: http://distro.ibiblio.org/damnsmall/mydsl/system/