QEMU: Difference between revisions
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→Usage: Mention the debugcon feature, remove bogus information on the "QEMU console", integrate the salvageable parts (serial output goes to ctrl-alt-3 by default, there's no need to do file:CON – that's an obscure windows "feature") |
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The <tt>-m 128</tt> argument instructs QEMU to create the guest system with 128MB of RAM. The <tt>-drive format=raw,media=cdrom,file=myos.iso</tt> argument instructs QEMU to create a drive in our guest system. In this case the created drive is a CDROM drive, with <tt>myos.iso</tt> as its loaded media. If more than one drive in is required in the guest system, it is possible to use the <tt>-boot</tt> option to define the order in which the system will check for bootable media. |
The <tt>-m 128</tt> argument instructs QEMU to create the guest system with 128MB of RAM. The <tt>-drive format=raw,media=cdrom,file=myos.iso</tt> argument instructs QEMU to create a drive in our guest system. In this case the created drive is a CDROM drive, with <tt>myos.iso</tt> as its loaded media. If more than one drive in is required in the guest system, it is possible to use the <tt>-boot</tt> option to define the order in which the system will check for bootable media. |
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The <tt>-serial stdio</tt> argument used above instructs QEMU to redirect the serial input and output to the host system's <tt>stdio</tt> stream. This is particularly useful for debugging purposes. |
The <tt>-serial stdio</tt> argument used above instructs QEMU to redirect the serial input and output to the host system's <tt>stdio</tt> stream. This is particularly useful for debugging purposes. In the documentation, the option to redirect this to <tt>stdio</tt> is described as Unix only. Presumably, one should be able to achieve a similar effect with <tt>-serial file:CON</tt> on Windows. |
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In order to help track down the source of a triple fault, the <tt>-d int</tt> option can be used to show additional debugging information on interrupts that occur. Additionally, the <tt>-no-shutdown</tt> and <tt>-no-reboot</tt> options can be used. These instruct the virtual machine to halt on error instead of rebooting or shutting down, allowing for the operator to inspect the state of the machine after a triple-fault. |
In order to help track down the source of a triple fault, the <tt>-d int</tt> option can be used to show additional debugging information on interrupts that occur. Additionally, the <tt>-no-shutdown</tt> and <tt>-no-reboot</tt> options can be used. These instruct the virtual machine to halt on error instead of rebooting or shutting down, allowing for the operator to inspect the state of the machine after a triple-fault. |
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Additional useful command-line options are listed within the [[QEMU#Useful_QEMU_command-line_options|Useful QEMU command-line options]] section. |
Additional useful command-line options are listed within the [[QEMU#Useful_QEMU_command-line_options|Useful QEMU command-line options]] section. |
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The keyboard shortcuts <tt>CTRL-ALT-{1,2,3}</tt> can be used inside the emulator to swap in/out of the emulation screen, the QEMU |
The keyboard shortcuts <tt>CTRL-ALT-{1,2,3}</tt> can be used inside the emulator to swap in/out of the emulation screen, the QEMU monitor and a serial console. Additional debugging commands can be issued from the system console, such as changing disk images and performing memory dumps, among others. |
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===The |
===The debug console=== |
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Instead of the serial port, as outlined above, one can also use the <tt>debugcon</tt> device. By running QEMU with <tt>-debugcon stdio</tt>, you can print a message to your host system's terminal by just writing each byte to port 0xe9. This is the same port as the one used by [[Bochs#I/O_debugger_macros|the equivalent feature in Bochs]]. |
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QEMU's internal console can be accessed by the key combination <tt>CTRL-ALT-3</tt> within QEMU. |
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Unlike the serial port, the debug console is one-way – you can only output. On the flip side, implementing support is much easier, and outputting the messages isn't artificially throttled by a baudrate. |
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Unlike [[Bochs]], QEMU does not provide an [[Port IO|IO port]] for communicating directly with its internal console. Output to the internal console can be accomplished by the redirection of serial output. Using the following command-line option will redirect COM1's output to the QEMU console: |
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<source lang="bash"> |
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-serial file:CON |
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</source> |
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===The QEMU monitor=== |
===The QEMU monitor=== |
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