>КАК обновить

~
If you already have a previous version of the CD you are
downloading, jigdo can re-use files on the old CD that are also
present in the new image, and you do not need to download them
again. Mount the old CD ROM and enter the path it is mounted under
(e.g. `/mnt/cdrom').

Что-то вроде--
- скачал в ./ debian-502-i386-businesscard.{jigdo,template}
- в ./l/ смонтировал debian-500-i386-businesscard.iso

$ jigdo-file mi --jigdo debian-502-i386-businesscard.jigdo ./l/
Found 107 of the 154 files required by the template
Copied input files to temporary file `debian-502-i386-businesscard.tmp' - repeat command and supply more files to continue
$ _

Получил недособранный debian-502-i386-businesscard.tmp

...
jigdo-lite --noask --jigdo debian-502-i386-businesscard.jigdo --scan ./l
делает примерно то же и сразу кидается качать недостающие файлы.