Unable to clone SD card (Mac) - Raspberry Pi Forums

hi everybody!
i've followed bunch of guides using dd (on mac, os x, 10.9.4) clone pi sd card, isn't working. original works fine, each time have cloned thing, other 1 won't boot pi. there i'm missing?

same thing every time, though i've used dd command little differently each time.

starts load fine, gets kernel panic saying similar "no filesystem available mount root" , gives kernel/message dump.

i've got 1 screen, it's hard copy word word, can if help.

matter format copy sd ms-dos/fat prior writing image disk/drive?

have been doing.
1) insert original card machine
2) use diskutil list determine right card
3) issue: dd if=/dev/(r)disk# of=~/desktop/pi.img bs=1m(or 4 or 8)
4) eject card , insert test card
5) using disk utility, erase card, , let format 1 fat partition.
6) using disk utility, unmount card
7) issue: dd if=~/desktop/pi.img of=/dev/(r)disk# bs=1m(or 4 or 8)
8) eject card
goes fine, when stick in pi , turn on, same kernel panic.

block size? should not use parameter?
both cards same size, different classes. original class 10, while backup/testing card class 4. make difference?

in advance
ps. i'm using /dev/rdisk because 1 guide said faster, , million times faster /dev/disk. i've tried both ways, don't think that's issue.

are sd cards identical models , revisions same manufacturer?
sd cards labelled e.g. "4gb" can have wildly different sizes; people try read e.g. 3980mb sd card, , write 3850mb card, , image old card doesn't fit on new card.

edit: seen you've said they're different classes. in experience, cards same manufacturer have different sizes different classes

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