64 lines
2.3 KiB
ReStructuredText
64 lines
2.3 KiB
ReStructuredText
3270 devices
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============
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The 3270 is the classic 'green-screen' console of the mainframes (see the
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`IBM 3270 Wikipedia article <https://en.wikipedia.org/wiki/IBM_3270>`__).
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The 3270 data stream is not implemented within QEMU; the device only provides
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TN3270 (a telnet extension; see `RFC 854 <https://tools.ietf.org/html/rfc854>`__
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and `RFC 1576 <https://tools.ietf.org/html/rfc1576>`__) and leaves the heavy
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lifting to an external 3270 terminal emulator (such as ``x3270``) to make a
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single 3270 device available to a guest. Note that this supports basic
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features only.
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To provide a 3270 device to a guest, create a ``x-terminal3270`` linked to
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a ``tn3270`` chardev. The guest will see a 3270 channel device. In order
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to actually be able to use it, attach the ``x3270`` emulator to the chardev.
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Example configuration
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---------------------
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* Make sure that 3270 support is enabled in the guest's Linux kernel. You need
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``CONFIG_TN3270`` and at least one of ``CONFIG_TN3270_TTY`` (for additional
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ttys) or ``CONFIG_TN3270_CONSOLE`` (for a 3270 console).
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* Add a ``tn3270`` chardev and a ``x-terminal3270`` to the QEMU command line::
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-chardev socket,id=ch0,host=0.0.0.0,port=2300,wait=off,server=on,tn3270=on
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-device x-terminal3270,chardev=ch0,devno=fe.0.000a,id=terminal0
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* Start the guest. In the guest, use ``chccwdev -e 0.0.000a`` to enable
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the device.
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* On the host, start the ``x3270`` emulator::
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x3270 <host>:2300
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* In the guest, locate the 3270 device node under ``/dev/3270/`` (say,
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``tty1``) and start a getty on it::
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systemctl start serial-getty@3270-tty1.service
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This should get you an additional tty for logging into the guest.
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* If you want to use the 3270 device as the Linux kernel console instead of
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an additional tty, you can also append ``conmode=3270 condev=000a`` to
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the guest's kernel command line. The kernel then should use the 3270 as
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console after the next boot.
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Restrictions
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------------
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3270 support is very basic. In particular:
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* Only one 3270 device is supported.
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* It has only been tested with Linux guests and the x3270 emulator.
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* TLS/SSL is not supported.
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* Resizing on reattach is not supported.
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* Multiple commands in one inbound buffer (for example, when the reset key
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is pressed while the network is slow) are not supported.
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