Don't believe that part of the instructions. I don't currently have
access to edit the wiki page, which is fine by me, but you should know
they did create .zip files, not gzip files. The corrected procedure,
which takes up a bit more disk space is:
2. 'unzip xMc_3_30.zip' or 'unzip xMc_4_25.zip'
3. 'dd if=xMc_3_30.img of=/dev/your/sd/card bs=10M' or 'dd
if=xMc_3_30.img of=/dev/your/sd/card bs=10M'
The block size isn't all that critical, as long as it is large enough
to avoid the writes on your USB programmer from being flushed too
often and having you wait forever as the writes are committed to the
SD card. I find that bigger values are somewhat better, but don't go
over your free RAM.