Hello Thomas,

TH> Geht das? Eine vorhandene SD-Karte 16 GB im laufendem Betrieb auf eine
TH> 64GB-Karte klonen. Ein Kartenleser ist vorhanden. Pi 3b, Raspian
TH> (aktuell)

Deutsch:  Ja dass is moeglich, aber nicht schlimm.
Englisch: Yes that is possible, but not a good idea.

Desktop => Menu => Accessoiries => SD Card Copier.
From:  /dev/mmcblk0   That's the internal (16 GB) SDcardslot of the Pi.
To:    /dev/sda       That's the SDcard Reader/Writer you first inserted,
or To: /dev/sdb       That's the SDcard Reader/Writer you second inserts.

When doing this, you never get an exact copy, because of open files
at a running system in the mmcblk0 SDcard slot.
For a very first backup, this is almost the only way, as you need
a second card to boot from, to backup another properly.
So better use 2 microSDcard reader/writers and copy with DD from
/dev/sda to /dev/sdb. The right 2 commands at the command prompt are then:

sudo dd if=/dev/sda of=/dev/sdb bs=1M status=progress conv=noerr,sync [RETRUN]
sudo sync                                                             [RETURN]

Be sure the 16 GB source card is in the first inserted SDcardreader,
and the new 64 GB destination card is in the second inserted SDcardWriter.
You can check wich is sda and sdb with the same SDcard Copier tool,
but I don't trust that tool for real copying,
the DD command gives better 1:1 copies,
but you always have to check that afterwards.

DoNot forget to type the SYNC command when the copy is ready.
It is important to write the buffer to the destination correctly!
Note: the sync in the dd command is different from the sync command alone,
both are needed.
The bs=1M parameter is necessarry for speed and and less card wear.
bs=4096 is the smallest Block Size you can use safely.
Without the bs parameter, the default 512 bytes are used,
but that is very slow and it wears the card to much,
so always use a BlockSize greater than at least 4K, 1M or 4M are better.

After the te copy you can enlarge the EXT4 Linux partion with GPartEd,
but you have first to install that on your Pi.
sudo apt-get install geparted,
or use another Linux system for GPartEd and dd.

Sometimes two SDcards have not an identical size.
If the destination is a little bit smaller, you have first to change the last
partition on the source card a bit, to get it copied right on another card.
This is my 5 years experience of using many Pi's.

TH> Falls das im launfendem Betrieb nicht möglich ist: Wie eine 64er Karte
TH> am Mac vorbereiten (1 oder 2 Partionen?) und dann klonen? Einfach im
TH> Finder Daten kopiren wird woh nicht gehen - oder?

I do know too little of Apple Mac's ;-(.
Only RISC OS and Raspbian Linux at many Pi's.
Good luck.

Greetings from Henri from Arnhem.nl at the river Rhine.

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