The YubiKey can be mode-switched from the U2F-only mode using libu2f-host by sending some non-standardized commands.
echo -e '\x06\x00\x00\x00' | u2f-host -d -a sendrecv -c c0
The \x06 corresponds to mode 6 and the following modes are known:
0 OTP device only.
1 CCID device only.
2 OTP/CCID composite device.
3 U2F device only.
4 OTP/U2F composite device.
5 U2F/CCID composite device.
6 OTP/U2F/CCID composite device.
Add 80 to set MODE_FLAG_EJECT, for example: 81 is mode 1 (CCID-only) with MODE_FLAG_EJECT. To select another mode, replace \x06 with what you wish. For example, if you want to put the YubiKey into pure OTP-mode use the following:
echo -e '\x01\x00\x00\x00' | u2f-host -d -a sendrecv -c c0
For mode-switching in other modes (OTP, CCID or combo modes), we recommend the following libraries and command-line tools instead:
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For OTP-modes
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For CCID-modes
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If you prefer a GUI (for all modes)
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