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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="../shells/index.html"><strong aria-hidden="true">1.</strong> Shells</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../shells/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="../shells/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="../shells/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li></ol></li><li class="chapter-item expanded "><a href="../cli/index.html"><strong aria-hidden="true">2.</strong> CLI foo</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../cli/awk.html"><strong aria-hidden="true">2.1.</strong> awk</a></li><li class="chapter-item expanded "><a href="../cli/sed.html"><strong aria-hidden="true">2.2.</strong> sed</a></li><li class="chapter-item expanded "><a href="../cli/column.html"><strong aria-hidden="true">2.3.</strong> column</a></li><li class="chapter-item expanded "><a href="../cli/sort.html"><strong aria-hidden="true">2.4.</strong> sort</a></li><li class="chapter-item expanded "><a href="../cli/tr.html"><strong aria-hidden="true">2.5.</strong> tr</a></li><li class="chapter-item expanded "><a href="../cli/tac.html"><strong aria-hidden="true">2.6.</strong> tac</a></li><li class="chapter-item expanded "><a href="../cli/paste.html"><strong aria-hidden="true">2.7.</strong> paste</a></li></ol></li><li class="chapter-item expanded "><a href="../tools/index.html"><strong aria-hidden="true">3.</strong> Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../tools/tmux.html"><strong aria-hidden="true">3.1.</strong> tmux</a></li><li class="chapter-item expanded "><a href="../tools/screen.html"><strong aria-hidden="true">3.2.</strong> screen</a></li><li class="chapter-item expanded "><a href="../tools/emacs.html"><strong aria-hidden="true">3.3.</strong> emacs</a></li><li class="chapter-item expanded "><a href="../tools/gpg.html"><strong aria-hidden="true">3.4.</strong> gpg</a></li><li class="chapter-item expanded "><a href="../tools/radare2.html"><strong aria-hidden="true">3.5.</strong> radare2</a></li><li class="chapter-item expanded "><a href="../tools/qemu.html" class="active"><strong aria-hidden="true">3.6.</strong> qemu</a></li><li class="chapter-item expanded "><a href="../tools/pacman.html"><strong aria-hidden="true">3.7.</strong> pacman</a></li><li class="chapter-item expanded "><a href="../tools/dot.html"><strong aria-hidden="true">3.8.</strong> dot</a></li><li class="chapter-item expanded "><a href="../tools/ffmpeg.html"><strong aria-hidden="true">3.9.</strong> ffmpeg</a></li><li class="chapter-item expanded "><a href="../tools/gnuplot.html"><strong aria-hidden="true">3.10.</strong> gnuplot</a></li><li class="chapter-item expanded "><a href="../tools/restic.html"><strong aria-hidden="true">3.11.</strong> restic</a></li><li class="chapter-item expanded "><a href="../tools/qrencode.html"><strong aria-hidden="true">3.12.</strong> qrencode</a></li></ol></li><li class="chapter-item expanded "><a href="../process/index.html"><strong aria-hidden="true">4.</strong> Process management & inspection</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../process/lsof.html"><strong aria-hidden="true">4.1.</strong> lsof</a></li><li class="chapter-item expanded "><a href="../process/pidstat.html"><strong aria-hidden="true">4.2.</strong> pidstat</a></li><li class="chapter-item expanded "><a href="../process/pgrep.html"><strong aria-hidden="true">4.3.</strong> pgrep</a></li><li class="chapter-item expanded "><a href="../process/ps.html"><strong aria-hidden="true">4.4.</strong> ps</a></li><li class="chapter-item expanded "><a href="../process/pmap.html"><strong aria-hidden="true">4.5.</strong> pmap</a></li><li class="chapter-item expanded "><a href="../process/pstack.html"><strong aria-hidden="true">4.6.</strong> pstack</a></li><li class="chapter-item expanded "><a href="../process/taskset.html"><strong aria-hidden="true">4.7.</strong> taskset</a></li><li class="chapter-item expanded "><a href="../process/nice.html"><strong aria-hidden="true">4.8.</strong> nice</a></li></ol></li><li class="chapter-item expanded "><a href="../trace_profile/index.html"><strong aria-hidden="true">5.</strong> Trace and Profile</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../trace_profile/time.html"><strong aria-hidden="true">5.1.</strong> time</a></li><li class="chapter-item expanded "><a href="../trace_profile/strace.html"><strong aria-hidden="true">5.2.</strong> strace</a></li><li class="chapter-item expanded "><a href="../trace_profile/ltrace.html"><strong aria-hidden="true">5.3.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="../trace_profile/perf.html"><strong aria-hidden="true">5.4.</strong> perf</a></li><li class="chapter-item expanded "><a href="../trace_profile/oprofile.html"><strong aria-hidden="true">5.5.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="../trace_profile/callgrind.html"><strong aria-hidden="true">5.6.</strong> callgrind</a></li><li class="chapter-item expanded "><a href="../trace_profile/valgrind.html"><strong aria-hidden="true">5.7.</strong> valgrind</a></li></ol></li><li class="chapter-item expanded "><a href="../debug/index.html"><strong aria-hidden="true">6.</strong> Debug</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../debug/gdb.html"><strong aria-hidden="true">6.1.</strong> gdb</a></li><li class="chapter-item expanded "><a href="../debug/gdbserver.html"><strong aria-hidden="true">6.2.</strong> gdbserver</a></li></ol></li><li class="chapter-item expanded "><a href="../binary/index.html"><strong aria-hidden="true">7.</strong> Binary</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../binary/od.html"><strong aria-hidden="true">7.1.</strong> od</a></li><li class="chapter-item expanded "><a href="../binary/xxd.html"><strong aria-hidden="true">7.2.</strong> xxd</a></li><li class="chapter-item expanded "><a href="../binary/readelf.html"><strong aria-hidden="true">7.3.</strong> readelf</a></li><li class="chapter-item expanded "><a href="../binary/objdump.html"><strong aria-hidden="true">7.4.</strong> objdump</a></li><li class="chapter-item expanded "><a href="../binary/nm.html"><strong aria-hidden="true">7.5.</strong> nm</a></li></ol></li><li class="chapter-item expanded "><a href="../development/index.html"><strong aria-hidden="true">8.</strong> Development</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../development/c++filt.html"><strong aria-hidden="true">8.1.</strong> c++filt</a></li><li class="chapter-item expanded "><a href="../development/c++.html"><strong aria-hidden="true">8.2.</strong> c++</a></li><li class="chapter-item expanded "><a href="../development/glibc.html"><strong aria-hidden="true">8.3.</strong> glibc</a></li><li class="chapter-item expanded "><a href="../development/gcc.html"><strong aria-hidden="true">8.4.</strong> gcc</a></li><li class="chapter-item expanded "><a href="../development/git.html"><strong aria-hidden="true">8.5.</strong> git</a></li><li class="chapter-item expanded "><a href="../development/cmake.html"><strong aria-hidden="true">8.6.</strong> cmake</a></li><li class="chapter-item expanded "><a href="../development/make.html"><strong aria-hidden="true">8.7.</strong> make</a></li><li class="chapter-item expanded "><a href="../development/ld.so.html"><strong aria-hidden="true">8.8.</strong> ld.so</a></li><li class="chapter-item expanded "><a href="../development/symbolver.html"><strong aria-hidden="true">8.9.</strong> symbol versioning</a></li><li class="chapter-item expanded "><a href="../development/python.html"><strong aria-hidden="true">8.10.</strong> python</a></li><li class="chapter-item expanded "><a href="../development/gcov.html"><strong aria-hidden="true">8.11.</strong> gcov</a></li><li class="chapter-item expanded "><a href="../development/pgo.html"><strong aria-hidden="true">8.12.</strong> pgo</a></li></ol></li><li class="chapter-item expanded "><a href="../linux/index.html"><strong aria-hidden="true">9.</strong> Linux</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../linux/systemd.html"><strong aria-hidden="true">9.1.</strong> systemd</a></li><li class="chapter-item expanded "><a href="../linux/coredump.html"><strong aria-hidden="true">9.2.</strong> coredump</a></li><li class="chapter-item expanded "><a href="../linux/ptrace_scope.html"><strong aria-hidden="true">9.3.</strong> ptrace_scope</a></li><li class="chapter-item expanded "><a href="../linux/cryptsetup.html"><strong aria-hidden="true">9.4.</strong> cryptsetup</a></li><li class="chapter-item expanded "><a href="../linux/swap.html"><strong aria-hidden="true">9.5.</strong> swap</a></li><li class="chapter-item expanded "><a href="../linux/input.html"><strong aria-hidden="true">9.6.</strong> input</a></li><li class="chapter-item expanded "><a href="../linux/acl.html"><strong aria-hidden="true">9.7.</strong> acl</a></li><li class="chapter-item expanded "><a href="../linux/zfs.html"><strong aria-hidden="true">9.8.</strong> zfs</a></li><li class="chapter-item expanded "><a href="../linux/cpufreq.html"><strong aria-hidden="true">9.9.</strong> cpufreq</a></li><li class="chapter-item expanded "><a href="../linux/cups.html"><strong aria-hidden="true">9.10.</strong> cups</a></li></ol></li><li class="chapter-item expanded "><a href="../network/index.html"><strong aria-hidden="true">10.</strong> Network</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../network/ssh.html"><strong aria-hidden="true">10.1.</strong> ssh</a></li><li class="chapter-item expanded "><a href="../network/ss.html"><strong aria-hidden="true">10.2.</strong> ss</a></li><li class="chapter-item expanded "><a href="../network/tcpdump.html"><strong aria-hidden="true">10.3.</strong> tcpdump</a></li><li class="chapter-item expanded "><a href="../network/tshark.html"><strong aria-hidden="true">10.4.</strong> tshark</a></li><li class="chapter-item expanded "><a href="../network/firewall-cmd.html"><strong aria-hidden="true">10.5.</strong> firewall-cmd</a></li><li class="chapter-item expanded "><a href="../network/nftables.html"><strong aria-hidden="true">10.6.</strong> nftables</a></li></ol></li><li class="chapter-item expanded "><a href="../web/index.html"><strong aria-hidden="true">11.</strong> Web</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../web/html.html"><strong aria-hidden="true">11.1.</strong> html</a></li><li class="chapter-item expanded "><a href="../web/css.html"><strong aria-hidden="true">11.2.</strong> css</a></li><li class="chapter-item expanded "><a href="../web/chartjs.html"><strong aria-hidden="true">11.3.</strong> chartjs</a></li><li class="chapter-item expanded "><a href="../web/plotly.html"><strong aria-hidden="true">11.4.</strong> plotly</a></li></ol></li><li class="chapter-item expanded "><a href="../arch/index.html"><strong aria-hidden="true">12.</strong> Arch</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../arch/x86_64.html"><strong aria-hidden="true">12.1.</strong> x86_64</a></li><li class="chapter-item expanded "><a href="../arch/armv8.html"><strong aria-hidden="true">12.2.</strong> armv8</a></li><li class="chapter-item expanded "><a href="../arch/arm64.html"><strong aria-hidden="true">12.3.</strong> arm64</a></li><li class="chapter-item expanded "><a href="../arch/armv7.html"><strong aria-hidden="true">12.4.</strong> armv7</a></li><li class="chapter-item expanded "><a href="../arch/riscv.html"><strong aria-hidden="true">12.5.</strong> riscv</a></li></ol></li></ol>
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<h1 id="qemu1"><a class="header" href="#qemu1">qemu(1)</a></h1>
<p>All the examples & notes use <code>qemu-system-x86_64</code> but in most cases
this can be swapped with the system emulator for other architectures.</p>
<h2 id="keybindings"><a class="header" href="#keybindings">Keybindings</a></h2>
<p>Graphic mode:</p>
<pre><code class="language-markdown">Ctrl+Alt+g release mouse capture from VM
Ctrl+Alt+1 switch to display of VM
Ctrl+Alt+2 switch to qemu monitor
</code></pre>
<p>No graphic mode:</p>
<pre><code class="language-markdown">Ctrl+a h print help
Ctrl+a x exit emulator
Ctrl+a c switch between monitor and console
</code></pre>
<h2 id="vm-config-snippet"><a class="header" href="#vm-config-snippet">VM config snippet</a></h2>
<p>Following command-line gives a good starting point to assemble a VM:</p>
<pre><code>qemu-system-x86_64 \
-cpu host -enable-kvm -smp 4 \
-m 8G \
-vga virtio -display sdl,gl=on \
-boot menu=on \
-cdrom <iso> \
-hda <disk> \
-device qemu-xhci,id=xhci \
-device usb-host,bus=xhci.0,vendorid=0x05e1,productid=0x0408,id=capture-card
</code></pre>
<h3 id="cpu--ram"><a class="header" href="#cpu--ram">CPU & RAM</a></h3>
<pre><code class="language-bash"># Emulate host CPU in guest VM, enabling all supported host featured (requires KVM).
# List available CPUs `qemu-system-x86_64 -cpu help`.
-cpu host
# Enable KVM instead software emulation.
-enable-kvm
# Configure number of guest CPUs.
-smp <N>
# Configure size of guest RAM.
-m 8G
</code></pre>
<h3 id="graphic--display"><a class="header" href="#graphic--display">Graphic & Display</a></h3>
<pre><code class="language-bash"># Use sdl window as display and enable openGL context.
-display sdl,gl=on
# Use vnc server as display (eg on display `:42` here).
-display vnc=localhost:42
# Confifure virtio as 3D video graphic accelerator (requires virgl in guest).
-vga virtio
</code></pre>
<h3 id="boot-menu"><a class="header" href="#boot-menu">Boot Menu</a></h3>
<pre><code class="language-bash"># Enables boot menu to select boot device (enter with `ESC`).
-boot menu=on
</code></pre>
<h3 id="block-devices"><a class="header" href="#block-devices">Block devices</a></h3>
<pre><code class="language-bash"># Attach cdrom drive with iso to a VM.
-cdrom <iso>
# Attach disk drive to a VM.
-hda <disk>
# Generic way to configure & attach a drive to a VM.
-drive file=<file>,format=qcow2
</code></pre>
<h4 id="create-a-disk-with-qemu-img"><a class="header" href="#create-a-disk-with-qemu-img">Create a disk with <a href="https://qemu-project.gitlab.io/qemu/tools/qemu-img.html"><code>qemu-img</code></a></a></h4>
<p>To create a <code>qcow2</code> disk (qemu copy-on-write) of size <code>10G</code>:</p>
<pre><code class="language-bash">qemu-img create -f qcow2 disk.qcow2 10G
</code></pre>
<p>The disk does not contain any <code>partitions</code> or a <code>partition table</code>.
We can format the disk from <strong>within the <strong>guest</strong></strong> as following example:</p>
<pre><code class="language-bash"># Create `gpt` partition table.
sudo parted /dev/sda mktable gpt
# Create two equally sized primary partitions.
sudo parted /dev/sda mkpart primary 0% 50%
sudo parted /dev/sda mkpart primary 50% 100%
# Create filesystem on each partition.
sudo mkfs.ext3 /dev/sda1
sudo mkfs.ext4 /dev/sda2
lsblk -f /dev/sda
NAME FSTYPE LABEL UUID FSAVAIL FSUSE% MOUNTPOINT
sda
├─sda1 ext3 ....
└─sda2 ext4 ....
</code></pre>
<h3 id="usb"><a class="header" href="#usb">USB</a></h3>
<h4 id="host-controller"><a class="header" href="#host-controller">Host Controller</a></h4>
<pre><code class="language-bash"># Add XHCI USB controller to the VM (supports USB 3.0, 2.0, 1.1).
# `id=xhci` creates a usb bus named `xhci`.
-device qemu-xhci,id=xhci
</code></pre>
<h4 id="usb-device"><a class="header" href="#usb-device">USB Device</a></h4>
<pre><code class="language-bash"># Pass-through USB device from host identified by vendorid & productid and
# attach to usb bus `xhci.0` (defined with controller `id`).
-device usb-host,bus=xhci.0,vendorid=0x05e1,productid=0x0408
</code></pre>
<h2 id="debugging"><a class="header" href="#debugging">Debugging</a></h2>
<pre><code class="language-bash"># Open gdbstub on tcp `<port>` (`-s` shorthand for `-gdb tcp::1234`).
-gdb tcp::<port>
# Freeze guest CPU at startup and wait for debugger connection.
-S
</code></pre>
<h2 id="io-redirection"><a class="header" href="#io-redirection">IO redirection</a></h2>
<pre><code class="language-bash"># Create raw tcp server for `serial IO` and wait until a client connects
# before executing the guest.
-serial tcp:localhost:12345,server,wait
# Create telnet server for `serial IO` and wait until a client connects
# before executing the guest.
-serial telnet:localhost:12345,server,wait
# Configure redirection for the QEMU `mointor`, arguments similar to `-serial`
# above.
-monitor ...
</code></pre>
<blockquote>
<p>In <code>server</code> mode use <code>nowait</code> to execute guest without waiting for a client
connection.</p>
</blockquote>
<h2 id="network"><a class="header" href="#network">Network</a></h2>
<pre><code class="language-bash"># Redirect host tcp port `1234` to guest port `4321`.
-nic user,hostfwd=tcp:localhost:1234-:4321
</code></pre>
<h2 id="shared-drives"><a class="header" href="#shared-drives">Shared drives</a></h2>
<pre><code class="language-bash"># Attach a `virtio-9p-pci` device to the VM.
# The guest requires 9p support and can mount the shared drive as:
# mount -t 9p -o trans=virtio someName /mnt
-virtfs local,id=someName,path=<someHostPath>,mount_tag=someName,security_model=none
</code></pre>
<h2 id="debug-logging"><a class="header" href="#debug-logging">Debug logging</a></h2>
<pre><code class="language-bash"># List debug items.
-d help
# Write debug log to file instead stderr.
-D <file>
# Examples
-d in_asm Log executed guest instructions.
</code></pre>
<h2 id="tracing"><a class="header" href="#tracing">Tracing</a></h2>
<pre><code class="language-bash"># List name of all trace points.
-trace help
# Enable trace points matching pattern and optionally write trace to file.
-trace <pattern>[,file=<file>]
# Enable trace points for all events listed in the <events> file.
# File must contain one event/pattern per line.
-trace events=<events>
</code></pre>
<h2 id="vm-snapshots"><a class="header" href="#vm-snapshots">VM snapshots</a></h2>
<p>VM snapshots require that there is at least on <code>qcow2</code> disk attached to the VM
(<a href="https://qemu-project.gitlab.io/qemu/system/images.html#vm-005fsnapshots">VM Snapshots</a>).</p>
<p>Commands for qemu <a href="https://qemu-project.gitlab.io/qemu/system/monitor.html">Monitor</a> or <a href="https://qemu-project.gitlab.io/qemu/interop/qemu-qmp-ref.html">QMP</a>:</p>
<pre><code class="language-bash"># List available snapshots.
info snapshots
# Create/Load/Delete snapshot with name <tag>.
savevm <tag>
loadvm <tag>
delvm <tag>
</code></pre>
<p>The snapshot can also be directly specified when invoking qemu as:</p>
<pre><code class="language-bash">qemu-system-x86_64 \
-loadvm <tag> \
...
</code></pre>
<h2 id="vm-migration"><a class="header" href="#vm-migration">VM Migration</a></h2>
<p><code>Online</code> migration example:</p>
<pre><code class="language-bash"># Start machine 1 on host ABC.
qemu-system-x86_64 -monitor stdio -cdrom <iso>
# Prepare machine 2 on host DEF as migration target.
# Listen for any connection on port 12345.
qemu-system-x86_64 -monitor stdio -incoming tcp:0.0.0.0:12345
# Start migration from the machine 1 monitor console.
(qemu) migrate tcp:DEF:12345
</code></pre>
<p>Save to external file example:</p>
<pre><code class="language-bash">```bash
# Start machine 1.
qemu-system-x86_64 -monitor stdio -cdrom <iso>
# Save VM state to file.
(qemu) migrate "exec:gzip -c > vm.gz"
# Load VM from file.
qemu-system-x86_64 -monitor stdio -incoming "exec: gzip -d -c vm.gz"
</code></pre>
<blockquote>
<p>The migration source machine and the migration target machine should be
launched with the <strong>same</strong> parameters.</p>
</blockquote>
<h2 id="appendix-direct-kernel-boot"><a class="header" href="#appendix-direct-kernel-boot">Appendix: Direct <code>Kernel</code> boot</a></h2>
<p>Example command line to directly boot a <code>Kernel</code> with an <code>initrd</code> ramdisk.</p>
<pre><code class="language-bash">qemu-system-x86_64 \
-cpu host \
-enable-kvm \
-kernel <dir>/arch/x86/boot/bzImage \
-append "earlyprintk=ttyS0 console=ttyS0 nokaslr init=/init debug" \
-initrd <dir>/initramfs.cpio.gz \
...
</code></pre>
<p>Instructions to build a minimal <a href="https://blog.memzero.de/kernel-debugging-qemu"><code>Kernel</code> and <code>initrd</code></a>.</p>
<h2 id="appendix-cheap-instruction-tracer"><a class="header" href="#appendix-cheap-instruction-tracer">Appendix: Cheap instruction tracer</a></h2>
<pre><code class="language-make">test: test.s
as -o test.o test.s
ld -o test test.o testc.o
trace: test
qemu-x86_64 -singlestep -d nochain,cpu ./test 2>&1 | awk '/RIP/ { print $$1; }'
clean:
$(RM) test test-bin test.o
</code></pre>
<pre><code class="language-x86asm">.section .text, "ax"
.global _start
_start:
xor %rax, %rax
mov $0x8, %rax
1:
cmp $0, %rax
je 2f
dec %rax
jmp 1b
2:
# x86-64 exit(2) syscall
mov $0, %rdi
mov $60, %rax
syscall
</code></pre>
<h2 id="references"><a class="header" href="#references">References</a></h2>
<ul>
<li><a href="https://github.com/qemu/qemu/blob/master/docs/usb2.txt">QEMU USB</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/tools/qemu-img.html">QEMU IMG</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/tools/index.html">QEMU Tools</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/system/index.html">QEMU System</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/system/invocation.html">QEMU Invocation (command line args)</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/system/monitor.html">QEMU Monitor</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/interop/qemu-qmp-ref.html">QEMU machine protocol (QMP)</a></li>
<li><a href="https://qemu-project.gitlab.io/qemu/system/images.html#vm-005fsnapshots">QEMU VM Snapshots</a></li>
</ul>
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