qemu: add/update examples

content/qemu/index.md

@@ -3,52 +3,117 @@ title = 'QEMU'
 icon = 'clanbomber'
 +++
 
-<a href="https://www.qemu.org/">QEMU</a> is an emulator for
-various CPUs. It works on Linux, Windows, FreeBSD and Mac OS X. It's possible
-to run grml with QEMU. Notice that it's much slower than running it native
-due to the emulation mode.
+[QEMU](https://www.qemu.org/) is an emulator for various CPUs.
+It works on Linux, Windows, FreeBSD and Mac OS X.
+It's possible to run Grml with QEMU.
+Note that it is slower than running it native due to the emulation mode.
 
 ## Using QEMU with acceleration
 
-grml >=0.5 provides the <a href="https://www.qemu.org/">accelerator module</a> for QEMU namend 'kqemu'. Just run the following commands to use it:
+On modern Linux distributions, including Grml, the kernel comes with an acceleration module, called `KVM`.
+To use this, load the `kvm.ko` kernel module, and give yourself rights:
 
 <pre class="rahmen">
-apt-get update ; apt-get install qemu # install qemu
-modprobe kqemu                        # load the kernel module
-mknod /dev/kqemu c 250 0              # create the device
-chmod 666 /dev/kqemu /dev/net/tun     # adjust permissions
+apt update && apt install qemu-system        # install qemu
+modprobe kvm                                 # load the kernel module
 </pre>
 
-To see if kqemu is enabled and working correctly, use the QEMU monitor command (press ctrl-alt-2): 'info kqemu'
+If you are not logged in locally (just SSH does not count), your user also must be in the `kvm` group:
+<pre class="rahmen">
+adduser $USER kvm                            # add your user to kvm group
+# now login again or try: newgrp kvm
+</pre>
+
+
+To see if kvm is enabled and working correctly, use the QEMU monitor command (press ctrl-alt-2): 'info kvm'
+
+## Usage examples
+
+In all examples below you can add `-nographic -vga none` to get the first serial console on your terminal.
+This might work better on arm64, where the Linux kernel by default expects a serial console, and less good on amd64.
+
+The example use `-m 2048` for 2GB (2048MB) of virtual memory (RAM).
+They do not pass any CPU core counts, so you get one virtualized CPU core.
+Use `-smp 2` to enable 2 CPU cores, for example.
+
+### Boot Grml ISO on arm64 (aarch64)
+
+This assumes the firmware shall be UEFI EDK2 ("TianoCore").
+This is the best supported QEMU target on arm64.
+
+This also assumes that your host is actually arm64 and has KVM support.
+
+<pre class="rahmen">
+apt update && apt install qemu-system qemu-system-gui qemu-efi-aarch64
+cp /usr/share/AAVMF/AAVMF_VARS.fd efi_vars.fd
+qemu-system-aarch64 \
+    -machine type=virt,gic-version=max,accel=kvm:tcg \
+    -cpu max \
+    -m 2048 \
+    -drive if=pflash,format=raw,unit=0,file.filename=/usr/share/AAVMF/AAVMF_CODE.no-secboot.fd,file.locking=off,readonly=on \
+    -drive if=pflash,unit=1,file=efi_vars.fd \
+    -monitor unix:qemu-monitor-socket,server,nowait \
+    -cdrom ~/grml-full-{{< param current_release.version >}}-arm64.iso
+</pre>
+
+To access the QEMU monitor, you can use socat on a separate terminal:
+
+<pre class="rahmen">
+apt update && apt install socat
+socat -,echo=0,icanon=0 unix-connect:qemu-monitor-socket
+</pre>
 
-## Problems with Qemu
+From there you can run commands like `info kvm` or `quit`.
 
-### Black / blank screen
+### Boot Grml ISO on amd64 (64-bit PC), UEFI
 
-You get a black/blank screen when booting grml in qemu? Try booting with &quot;grml vga=normal&quot;.
+This assumes the firmware shall be UEFI EDK2 ("TianoCore").
+This also assumes that your host is amd64 and has KVM support.
+
+We picked machine `q35` (over `i440fx`) as it is a more modern (mostly legacy-free) x86 machine.
+
+QEMU monitor will be available on stdout.
+
+<pre class="rahmen">
+apt update && apt install qemu-system qemu-system-gui ovmf
+cp /usr/share/OVMF/OVMF_VARS_4M.fd efi_vars.fd
+qemu-system-x86_64 \
+    -machine type=q35,accel=kvm:tcg \
+    -cpu max \
+    -m 2048 \
+    -drive if=pflash,format=raw,unit=0,file.filename=/usr/share/OVMF/OVMF_CODE_4M.fd,file.locking=off,readonly=on \
+    -drive if=pflash,unit=1,file="efi_vars.fd \
+    -monitor stdio \
+    -cdrom ~/grml-full-{{< param current_release.version >}}-amd64.iso
+</pre>
 
-## Running QEMU with grml on Linux
+### Boot Grml ISO on amd64 (64-bit PC), Legacy BIOS
 
-Install qemu (apt-get install qemu) and start it e.g. via:
+This will boot using legacy BIOS firmware, usually SeaBIOS.
 
 <pre class="rahmen">
-qemu -m 256 -cdrom /dev/hdc          # if running from CD-ROM
-qemu -m 256 -cdrom /path/to/grml.iso # if running from harddisk
+apt update && apt install qemu-system qemu-system-gui seabios
+qemu-system-x86_64 \
+    -machine type=q35,accel=kvm:tcg \
+    -cpu max \
+    -m 2048 \
+    -monitor stdio \
+    -cdrom ~/grml-full-{{< param current_release.version >}}-amd64.iso
 </pre>
 
-## Running QEMU with grml on Windows
+## Running Grml under QEMU on Windows
 
 <a href="qemu-1.png"><img style="border: 0" src="qemu-1.jpg" alt="screenshot 1" /></a>
 
 First of all download <a href="https://www.qemu.org/download/#windows">QEMU for Windows</a>.
-<a href="/download/">Download the grml-iso</a> and put the QEMU files in the same directory as the grml-iso.
+<a href="/download/">Download a Grml ISO</a> and put the QEMU files in the same directory as the Grml ISO.
 
 Now create a startup file, call it for example <a href="grml-qemu.bat">grml-qemu.bat</a>:
 
 <pre class="rahmen">
 REM Start qemu on windows.
 @ECHO OFF
-START qemu.exe -L . -m 256 -hdc harddisk -cdrom grml_0.6.iso
+START qemu.exe -L . -m 2048 -hdc harddisk -cdrom grml-full-{{< param current_release.version >}}-amd64.iso
 CLS
 EXIT
 </pre>