Difference between revisions of "Talk:QEMU"

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(Preparing an (Arch) Linux guest: linux-lts is now on 3.10.x)
(Creating bridge manually)
 
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:-- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 18:24, 5 September 2013 (UTC)
 
:-- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 18:24, 5 September 2013 (UTC)
  
==  Preparing an (Arch) Linux guest  ==
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:I would not remove something that works still heh.--[[User:Webdawg|Webdawg]] ([[User talk:Webdawg|talk]]) 07:31, 17 July 2016 (UTC)
  
adding the virtio modules to use virtual devices doesn't appear to be necessary as of the VM I built this week(Jul 26, 2013). Kernel 3.9.9-1
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== Starting QEMU virtual machines with systemd ==
[[User:Surlyjake|Surlyjake]] ([[User talk:Surlyjake|talk]]) 03:42, 27 July 2013 (UTC)
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:In newer kernel versions (I think since 3.4) the kernel modules are loaded automatically. I'd still keep the section as it is for now, linux-lts is still at 3.0. -- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 21:09, 20 August 2013 (UTC)
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::{{Pkg|linux-lts}} is now on the 3.10 series.
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::-- [[User:Jstjohn|Jstjohn]] ([[User talk:Jstjohn|talk]]) 16:51, 23 September 2013 (UTC)
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== Starting QEMU virtual machines with Systemd  ==
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The custom systemd service script does not work. It always fails with {{ic|Failed at step EXEC spawning /usr/bin/qemu-{type}: No such file or directory}}. To Fix this modify the ExecStart command {{bc|1=ExecStart=/usr/bin/sh -c "/usr/bin/qemu-${type} -name %i -nographic ${args}"}}
 
The custom systemd service script does not work. It always fails with {{ic|Failed at step EXEC spawning /usr/bin/qemu-{type}: No such file or directory}}. To Fix this modify the ExecStart command {{bc|1=ExecStart=/usr/bin/sh -c "/usr/bin/qemu-${type} -name %i -nographic ${args}"}}
Also {{ic|echo 'system_powerdown' | nc localhost 7101}} kills the VM immediatly. To fix this change the stop script. It simply checks each second if the main process is still running. {{bc|1=ExecStop=/usr/bin/sh -c "${haltcmd} && while [[ `pidof qemu-${type} | grep $MAINPID` ]]; do sleep 1; done"}}
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Also {{ic|echo 'system_powerdown' | nc localhost 7101}} kills the VM immediatly. To fix this change the stop script. It simply checks each second if the main process is still running. {{bc|1=ExecStop=/usr/bin/sh -c "${haltcmd} && while [[ $(pidof qemu-${type} | grep $MAINPID) ]]; do sleep 1; done"}}
 
{{ic|gnu-netcat}} does not work to connect to the monitor. You need to use {{ic|openbsd-netcat}}. -- [[User:Ant32|Ant32]] ([[User talk:Ant32|talk]]) 17:48, 5 September 2013 (UTC)
 
{{ic|gnu-netcat}} does not work to connect to the monitor. You need to use {{ic|openbsd-netcat}}. -- [[User:Ant32|Ant32]] ([[User talk:Ant32|talk]]) 17:48, 5 September 2013 (UTC)
  
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::Relevant thread on systemd-devel mailing list: [http://lists.freedesktop.org/archives/systemd-devel/2013-September/012982.html] -- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 00:00, 15 September 2013 (UTC)
 
::Relevant thread on systemd-devel mailing list: [http://lists.freedesktop.org/archives/systemd-devel/2013-September/012982.html] -- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 00:00, 15 September 2013 (UTC)
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== Kexec Hackery When Using a Real Partition ==
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After banging my head against a wall long enough and figuring out what {{ic|-kernel}} and {{ic|-initrd}} were really calling, I put a note above the appropriate section and mentioned two ways to use the guest's images.  (Otherwise, you'll have to worry if the host and guest images match.)  The first -- mount the partition(s) -- is more appropriate for "low-volume-handling" of VMs.  The second -- using kexec -- becomes more useful when you're juggling more than a few VMs.
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I'm only mentioning this hack because (as of now) [[Kexec]] only mentions use for rebooting into another kernel, not switching out the kernel before the system is even up.  This hack comes from from https://digitalocean.uservoice.com/forums/136585-digitalocean/suggestions/2814988-give-option-to-use-the-droplet-s-own-bootloader- which has two suggestions.  The most recent, using systemd units by jkuan, doesn't work because jkuan tried to copy a {{ic|.target}} file into a {{ic|.service}} file and systemd wants {{ic|ExecStart}} in a {{ic|.service}} file.  The second one, replacing {{ic|/usr/bin/init}} by andrew_sparks, works for me on my Arch instance at DigitalOcean.
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Adaptation from said post:
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# pacman -S kexec-tools
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# pacman -R systemd-sysvcompat
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{{hc|1=/tmp/init|2=
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#!/bin/sh
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kexec --load /boot/vmlinuz-linux --initrd=/boot/initramfs-linux.img --append="root=/dev/sda init=/usr/lib/systemd/systemd" &&
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mount -o ro,remount / && kexec -e
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exec /usr/lib/systemd/systemd
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}}
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# cd [/path/to/vm]/usr/bin
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# mv init init.dist
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# cp /tmp/init ./
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# chmod 755 init
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I'm leaving this on the Talk page as I haven't even tried it out in QEMU myself.  Also, my eyes are about ready to pop out of my head, so I'm barring myself from figuring out the appropriate way to edit this in for the time being. [[User:BrainwreckedTech|BrainwreckedTech]] ([[User talk:BrainwreckedTech|talk]]) 21:23, 14 January 2014 (UTC)
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== Replace -net with -netdev ==
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The {{ic|-net}} option is deprecated and replaced by {{ic|-netdev}}. I think this article should be modified to reflect that.
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http://en.wikibooks.org/wiki/QEMU/Networking#cite_ref-1
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[[User:Axper|axper]] ([[User talk:Axper|talk]]) 18:12, 1 July 2014 (UTC)
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== I'm rewriting the network section ==
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https://wiki.archlinux.org/index.php/User:Axper/sandbox/qemu_network
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[[User:Axper|axper]] ([[User talk:Axper|talk]]) 20:07, 2 July 2014 (UTC)
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::I think a lot of networking topics could be moved outside of the QEMU page. Many virtualization applications share the same basic principles with regards to networking, such as tun/tap creating, bridges, VDE, etc. There are a few networking schemes that are QEMU-specific, for example multicast sockets and {{ic|-net socket,...}}, and these could be mentioned on the QEMU page, although these are less reliable and rarely used in comparison to tap devices. We should also of course note the QEMU-specific command line options in the QEMU page, but for general concepts and commands independent of the virtualization applications, they could go on pages dedicated to the task. The best example is VDE, which is in no way limited to QEMU, yet it still doesn't have its own page on the Arch wiki.
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::Incidentally, I'm planning on rewriting [[User Mode Linux]] (yes, I promise I will get around to it), which happens to share the "tap with bridge" and VDE concepts with QEMU. It would be nice if I could link to pages dedicated to those topics and only write UML-specific commands in the page, instead of duplicating a bunch of general information. I'm not familiar very familiar with Xen or LXC or Docker or the like, but I would suspect that they also share some networking infrastructure. We could possibly even create a category just for these types of pages, for example "Virtual Networking" or "Advanced Networking". [[User:EscapedNull|EscapedNull]] ([[User talk:EscapedNull|talk]]) 13:32, 19 February 2015 (UTC)
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== -enable-kvm vs -machine type=pc,accel=kvm ==
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The section [[QEMU#Enabling_KVM]] recommends {{ic|-enable-kvm}}, while [[QEMU#Virtual_machine_runs_too_slowly]] recommends {{ic|1=-machine type=pc,accel=kvm}}. Is there any difference between the two? Is one preferred over the other? Should we just link to the former section from the latter (and possibly move both command line switches to the same section)? [[User:EscapedNull|EscapedNull]] ([[User talk:EscapedNull|talk]]) 17:23, 18 January 2015 (UTC)
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== virtio-gpu ==
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Any tutorial on using the new virtio-gpu which is introduced in qemu-2.4 and kernel 4.2? [[User:Adam900710|Adam900710]] ([[User talk:Adam900710|talk]]) 02:44, 19 August 2015 (UTC)
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== host only networking ==
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I added a quick and easy method but it was deleted.  I found errors in what is here. Is it worth my time to correct them or will they be deleted? {{unsigned|16:39, 4 January 2016‎|Netskink}}
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:You are welcome to make any corrections. Nobody can tell you if they will be kept or reverted beforehand, but if you're afraid to waste your time feel free to just point them out using an [[Help:Template|Article status templates|article status template]] (should be less time consuming). -- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 22:28, 21 February 2016 (UTC)
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== <s>Qemu-bridge-helper broken QENU 2.5.0-1</s> ==
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/etc/qemu/bridge.conf.sample does not exist, therefore the wiki entry is impossible to follow.
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I have tried to find this file on the internet with no sucess.
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--[[User:DontPanic|DontPanic]] ([[User talk:DontPanic|talk]]) 18:34, 5 April 2016 (UTC)
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:This appears to be {{Bug|46791}}. – [[User:Kynikos|Kynikos]] ([[User talk:Kynikos|talk]]) 00:58, 7 April 2016 (UTC)
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::The sample file was removed deliberately from the package in [https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/qemu&id=c5ecbacc08a113fbdc54a0e25babb391f36cd6db] and the wiki has been updated, closing. -- [[User:Lahwaacz|Lahwaacz]] ([[User talk:Lahwaacz|talk]]) 08:35, 4 June 2016 (UTC)

Latest revision as of 07:31, 17 July 2016

Linear RAID

When I was updating the article yesterday, I had tried to fit the section about linear raid (boot a VM from a partition by prepending a MBR to it) into the article better. But I'm not sure the technique described is the right one at all. It looks like it works, but wouldn't it be easier to install a bootloader directly to the partition (e.g. syslinux)? Then the VM could be booted directly from the partition simply by using it as its virtual disk. --Synchronicity (talk) 19:23, 9 May 2012 (UTC)

Creating bridge manually

I really don't know what to do with this section. I'd say it has been superseded by QEMU#Creating bridge using qemu-bridge-helper (available since qemu-1.1, we now have qemu-1.5) - or is someone still using this method? Perhaps link to https://en.wikibooks.org/wiki/QEMU/Networking#TAP_interfaces or http://wiki.qemu.org/Documentation/Networking/NAT is sufficient. What do you think? -- Lahwaacz (talk) 20:42, 22 July 2013 (UTC)

Actually, I've become a happy user of this method. I've written some scripts to easily create bridge interface, TAP interface, and combined with Xyne's excellent scripts to set up NAT and launch DHCP server, I have complete solution to easily manage multiple VMs on one (or even more) bridge.
My scripts are available on github: [1], [2], [3] but I won't probably integrate them into the wiki, I'l just leave a note when I do some more testing.
The thing is, what to do with the current content? Personally I think that links to [4], [5] and my scripts are sufficient (of course others are welcome). I'd also leave the note at the end to disable the firewall on the bridge, I find it extremely useful.
-- Lahwaacz (talk) 18:24, 5 September 2013 (UTC)
I would not remove something that works still heh.--Webdawg (talk) 07:31, 17 July 2016 (UTC)

Starting QEMU virtual machines with systemd

The custom systemd service script does not work. It always fails with Failed at step EXEC spawning /usr/bin/qemu-{type}: No such file or directory. To Fix this modify the ExecStart command
ExecStart=/usr/bin/sh -c "/usr/bin/qemu-${type} -name %i -nographic ${args}"
Also echo 'system_powerdown' | nc localhost 7101 kills the VM immediatly. To fix this change the stop script. It simply checks each second if the main process is still running.
ExecStop=/usr/bin/sh -c "${haltcmd} && while [[ $(pidof qemu-${type} | grep $MAINPID) ]]; do sleep 1; done"

gnu-netcat does not work to connect to the monitor. You need to use openbsd-netcat. -- Ant32 (talk) 17:48, 5 September 2013 (UTC)

The first problem related to starting the service seems rather strange - didn't you have typo error in your local qemu@.service file (missing the dollar sign $ in ${type} )?
The second problem is valid, systemd kills the main process when the ExecStop command exits (see systemd.service(5)). If your workaround really works, it could be added to the wiki with a proper description.
-- Lahwaacz (talk) 21:17, 7 September 2013 (UTC)
Relevant thread on systemd-devel mailing list: [6] -- Lahwaacz (talk) 00:00, 15 September 2013 (UTC)

Kexec Hackery When Using a Real Partition

After banging my head against a wall long enough and figuring out what -kernel and -initrd were really calling, I put a note above the appropriate section and mentioned two ways to use the guest's images. (Otherwise, you'll have to worry if the host and guest images match.) The first -- mount the partition(s) -- is more appropriate for "low-volume-handling" of VMs. The second -- using kexec -- becomes more useful when you're juggling more than a few VMs.

I'm only mentioning this hack because (as of now) Kexec only mentions use for rebooting into another kernel, not switching out the kernel before the system is even up. This hack comes from from https://digitalocean.uservoice.com/forums/136585-digitalocean/suggestions/2814988-give-option-to-use-the-droplet-s-own-bootloader- which has two suggestions. The most recent, using systemd units by jkuan, doesn't work because jkuan tried to copy a .target file into a .service file and systemd wants ExecStart in a .service file. The second one, replacing /usr/bin/init by andrew_sparks, works for me on my Arch instance at DigitalOcean.

Adaptation from said post:

# pacman -S kexec-tools
# pacman -R systemd-sysvcompat
/tmp/init
#!/bin/sh

kexec --load /boot/vmlinuz-linux --initrd=/boot/initramfs-linux.img --append="root=/dev/sda init=/usr/lib/systemd/systemd" &&
mount -o ro,remount / && kexec -e
exec /usr/lib/systemd/systemd
# cd [/path/to/vm]/usr/bin
# mv init init.dist
# cp /tmp/init ./
# chmod 755 init

I'm leaving this on the Talk page as I haven't even tried it out in QEMU myself. Also, my eyes are about ready to pop out of my head, so I'm barring myself from figuring out the appropriate way to edit this in for the time being. BrainwreckedTech (talk) 21:23, 14 January 2014 (UTC)

Replace -net with -netdev

The -net option is deprecated and replaced by -netdev. I think this article should be modified to reflect that. http://en.wikibooks.org/wiki/QEMU/Networking#cite_ref-1 axper (talk) 18:12, 1 July 2014 (UTC)

I'm rewriting the network section

https://wiki.archlinux.org/index.php/User:Axper/sandbox/qemu_network axper (talk) 20:07, 2 July 2014 (UTC)

I think a lot of networking topics could be moved outside of the QEMU page. Many virtualization applications share the same basic principles with regards to networking, such as tun/tap creating, bridges, VDE, etc. There are a few networking schemes that are QEMU-specific, for example multicast sockets and -net socket,..., and these could be mentioned on the QEMU page, although these are less reliable and rarely used in comparison to tap devices. We should also of course note the QEMU-specific command line options in the QEMU page, but for general concepts and commands independent of the virtualization applications, they could go on pages dedicated to the task. The best example is VDE, which is in no way limited to QEMU, yet it still doesn't have its own page on the Arch wiki.
Incidentally, I'm planning on rewriting User Mode Linux (yes, I promise I will get around to it), which happens to share the "tap with bridge" and VDE concepts with QEMU. It would be nice if I could link to pages dedicated to those topics and only write UML-specific commands in the page, instead of duplicating a bunch of general information. I'm not familiar very familiar with Xen or LXC or Docker or the like, but I would suspect that they also share some networking infrastructure. We could possibly even create a category just for these types of pages, for example "Virtual Networking" or "Advanced Networking". EscapedNull (talk) 13:32, 19 February 2015 (UTC)

-enable-kvm vs -machine type=pc,accel=kvm

The section QEMU#Enabling_KVM recommends -enable-kvm, while QEMU#Virtual_machine_runs_too_slowly recommends -machine type=pc,accel=kvm. Is there any difference between the two? Is one preferred over the other? Should we just link to the former section from the latter (and possibly move both command line switches to the same section)? EscapedNull (talk) 17:23, 18 January 2015 (UTC)

virtio-gpu

Any tutorial on using the new virtio-gpu which is introduced in qemu-2.4 and kernel 4.2? Adam900710 (talk) 02:44, 19 August 2015 (UTC)

host only networking

I added a quick and easy method but it was deleted. I found errors in what is here. Is it worth my time to correct them or will they be deleted? —This unsigned comment is by Netskink (talk) 16:39, 4 January 2016‎. Please sign your posts with ~~~~!

You are welcome to make any corrections. Nobody can tell you if they will be kept or reverted beforehand, but if you're afraid to waste your time feel free to just point them out using an Article status templates|article status template (should be less time consuming). -- Lahwaacz (talk) 22:28, 21 February 2016 (UTC)

Qemu-bridge-helper broken QENU 2.5.0-1

/etc/qemu/bridge.conf.sample does not exist, therefore the wiki entry is impossible to follow.

I have tried to find this file on the internet with no sucess.

--DontPanic (talk) 18:34, 5 April 2016 (UTC)

This appears to be FS#46791. – Kynikos (talk) 00:58, 7 April 2016 (UTC)
The sample file was removed deliberately from the package in [7] and the wiki has been updated, closing. -- Lahwaacz (talk) 08:35, 4 June 2016 (UTC)