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doc:appunti:linux:sa:virtualization [2011/12/14 12:22] – [Using KVM with libvirt: start, stop and ACPI] niccolodoc:appunti:linux:sa:virtualization [2019/08/28 12:03] – [Libvirt to manage KVM hosts: install, start, stop] niccolo
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   * [[qemu]]   * [[qemu]]
   * [[xen]]   * [[xen]]
- +  * [[qemu_kvm]]
  
 ===== Linux kernel KVM ===== ===== Linux kernel KVM =====
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 La scheda di rete emulata ha bisogno di opportuni driver nella macchina guest. Linux offre nativamente il supporto per tale scheda di rete (virtio-net), mentre con sistemi MS-Windows bisogna procurarsi i driver {{.:software:kvm-guest-drivers-windows-2.zip|kvm-guest-drivers-windows-2.zip}} dal repository di [[http://sourceforge.net/projects/kvm/|Linux KVM]]. La scheda di rete emulata ha bisogno di opportuni driver nella macchina guest. Linux offre nativamente il supporto per tale scheda di rete (virtio-net), mentre con sistemi MS-Windows bisogna procurarsi i driver {{.:software:kvm-guest-drivers-windows-2.zip|kvm-guest-drivers-windows-2.zip}} dal repository di [[http://sourceforge.net/projects/kvm/|Linux KVM]].
 +
 ==== Modalità network ==== ==== Modalità network ====
  
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 </code> </code>
  
-FIXME Pare che la riserva di indirizzo con **''host mac''** non venga onorata da libvirt/kvm. Vedere [[http://libvirt.org/formatnetwork.html|Network XML format]].+Dopo aver cambiato il file di configurazione **non basta riavviare** il servizio libvirt-bin, perché l'istanza di **dnsmasq** che gestisce il DHCP **non viene riavviata**. La procedura corretta dovrebbe essere quella di riavviare la rete virtuale //default// dalla **virsh**, con i comandi **''net-destroy default''** e **''net-start default''**, ma si deve fare attenzione alle macchine virtuali in esecuzione (perdono l'accesso alla rete?). È possibile killare il processo dnsmasq e riavviarlo con i parametri nuovi impostandoli manualmente. 
 ===== Starting a KVM virtual machine on an headless host ===== ===== Starting a KVM virtual machine on an headless host =====
  
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 After the virtual host is running, use **''screen -r''** to attach the console on the virtual serial line, or (better) do a remote login via ssh. After the virtual host is running, use **''screen -r''** to attach the console on the virtual serial line, or (better) do a remote login via ssh.
  
-===== Using KVM with libvirt: start, stop and ACPI =====+===== Libvirt to manage KVM hosts: install, start, stop =====
  
 The **libvirt** toolkit allow to manage some virtualization systems (namely **xen**, **qemu** and **kvm**) in a consistent and uniform way. It provides an infrastructure to manage virtual machines: create, start, destroy, shutdown, ... The **libvirt** toolkit allow to manage some virtualization systems (namely **xen**, **qemu** and **kvm**) in a consistent and uniform way. It provides an infrastructure to manage virtual machines: create, start, destroy, shutdown, ...
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 <code> <code>
-virt-install --name=virtual_lenny \ +virt-install \ 
-    --ram 384 \ +    --name virtual_lenny \ 
-    --file=/home/kvm/virtual_lenny.img --file-size 3 \ +    --virt-type kvm \ 
-    --accelerate --hvm --vnc+    --memory 1024 \ 
 +    --disk /home/kvm/virtual_lenny.img,size=3 \ 
 +    --cdrom /var/lib/libvirt/images/debian-10.0.0-amd64-netinst.iso \ 
 +    --os-variant auto \ 
 +    --network bridge=br0 \ 
 +    --vnc
 </code> </code>
 +
 +The disk size is specified in **Gibabytes**, the network uses the **bridge mode** via the **br0** interface. If you don't specify the **%%--network%%** option, it will use the **network mode** named //default//. You can also use the option **%%--network none%%**.
  
 See the man page for using a CD-ROM boot image, etc. Now list the existing virtual machines and connect to the VNC console with the viewer (it requires X forward): See the man page for using a CD-ROM boot image, etc. Now list the existing virtual machines and connect to the VNC console with the viewer (it requires X forward):
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 </code> </code>
  
-The **virt-install** simply creates an xml file into **''/etc/libvirt/qemu/virtual_lenny.xml''**. In this example the orginal file was modified by hand. See the [[http://www.libvirt.org/formatdomain.html|syntax documentation]].+The **virt-install** creates the xml configuration file into **/etc/libvirt/qemu/virtual_lenny.xml** and creates the virtual disk file into **/home/virt/virtual_lenny.img**. 
 + 
 +In the following example the orginal file created by ''virt-install'' was partially modified by hand. See the [[http://www.libvirt.org/formatdomain.html|syntax documentation]].
  
 <code xml> <code xml>
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   <vcpu>1</vcpu>   <vcpu>1</vcpu>
   <os>   <os>
-    <type>hvm</type>+    <type arch='x86_64' machine='pc'>hvm</type>
     <boot dev='hd'/>     <boot dev='hd'/>
   </os>   </os>
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       <script path='no'/>       <script path='no'/>
     </interface>     </interface>
-    <graphics type='vnc' port='-1' listen='127.0.0.1'/>+    <graphics type='vnc' port='autoport' listen='127.0.0.1'/>
     <serial type="null">     <serial type="null">
     </serial>     </serial>
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 </code> </code>
  
-The VNC port can be assigned automatically (seting it to **''%%port='-1'%%''**), or assigned statically, e.g. **''%%port='5901'%%''**.+**NOTICE**: The attributes **arch** and **machine** of tag **%%<os><type>%%** are madatory with **Libvirt 3.0.0** (provided by **Debian 9 Stretch**), they were instead not required in previous versions. To view the the list of supported machines, execute **''qemu-system-x86_64  -machine help''**. 
 + 
 +The VNC port can be assigned automatically (seting it to **''%%port='autoport'%%''**), or assigned statically, e.g. **''%%port='5901'%%''**. 
 + 
 +The **%%<os><type>%%** and **%%<cpu>%%** tags of the XML configuration file, determines what CPU is offered to the guest machine. Here it is the default choosed by ''virt-install'' on a Xeon host (Debian 10 Buster with libvirt 5.0): 
 + 
 +<code xml> 
 +  <os> 
 +    <type arch='x86_64' machine='pc'>hvm</type> 
 +  </os> 
 +  <cpu mode='host-model' check='partial'> 
 +    <model fallback='allow'/> 
 +  </cpu> 
 +</code> 
 + 
 +You can use a **specific option** if you have an **Intel CPU**: 
 + 
 +<code xml> 
 +  <cpu mode='custom' match='exact'> 
 +    <model fallback='allow'>Skylake-Client</model> 
 +  </cpu> 
 +</code> 
 + 
 +or this one if you have an **AMD CPU**: 
 + 
 +<code xml> 
 +  <cpu mode='custom' match='exact'> 
 +    <model fallback='allow'>Opteron_G3</model> 
 +  </cpu> 
 +</code> 
 + 
 +===== Libvirt and ACPI =====
  
 The nice thing is that you can control automatic start and stop of the virtual machines. Install the **acpid** package on the virtual host and load the **button** kernel module. Then you can start a shutdown sequence on the virtual host issuing the following command on the hosting machine: The nice thing is that you can control automatic start and stop of the virtual machines. Install the **acpid** package on the virtual host and load the **button** kernel module. Then you can start a shutdown sequence on the virtual host issuing the following command on the hosting machine:
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 virsh shutdown virtual_lenny virsh shutdown virtual_lenny
 </code> </code>
 +
 +The default shutdown of the host machine, will perform a clean shutdown of the guest machines.
  
 ==== Connecting to the virtual host ==== ==== Connecting to the virtual host ====
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       <script path='no'/>       <script path='no'/>
     </interface>     </interface>
-    <graphics type='vnc' port='-1' listen='192.168.2.7'/>+    <graphics type='vnc' port='autoport' listen='192.168.2.7'/>
     <serial type="null">     <serial type="null">
     </serial>     </serial>
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   * [[https://bugzilla.redhat.com/show_bug.cgi?id=517938| Cannot install KVM guests over NFS (rtl8139 emulation)]]   * [[https://bugzilla.redhat.com/show_bug.cgi?id=517938| Cannot install KVM guests over NFS (rtl8139 emulation)]]
   * [[http://www.linux-kvm.org/page/Virtio|Virtio]]   * [[http://www.linux-kvm.org/page/Virtio|Virtio]]
 +
 +===== Problema di timeout su disco =====
 +
 +Se la piattaforma ospitante è troppo carica (o forse se vengono effettuate operazioni di migrazione della macchina virtuale?), può accadere che il disco virtuale non risponda per diversi secondi. Ecco il messaggio registrato da ''dmesg'':
 +
 +<code>
 +[100449.816153] ata1: lost interrupt (Status 0x50)
 +[100467.710383] end_request: I/O error, dev sda, sector 43343336
 +[100467.710922] Aborting journal on device sda3-8.
 +[100467.712097] EXT4-fs error (device sda3): ext4_journal_start_sb: Detected aborted journal
 +[100467.712594] EXT4-fs (sda3): Remounting filesystem read-only
 +[100469.754031] EXT4-fs error (device sda3) in ext4_da_writepages: IO failure
 +[100469.754676] EXT4-fs (sda3): ext4_da_writepages: jbd2_start: 840 pages, ino 138323; err -30
 +</code>
 +
 +In tal caso è possibile incrementare il timeout predefinito di **30 secondi**:
 +
 +<code>
 +echo 180 > /sys/block/sda/device/timeout
 +</code>
 +
 +Per rendere permanente questa modifica in Debian si può installare il pacchetto **sysfsutils** e aggiungere questa riga al file **''/etc/sysfs.conf''**:
 +
 +<file>
 +block/sda/device/timeout = 180
 +</file>
 +
 +C'è chi suggerisce addirittura timeout di 900 secondi.
 +
 +===== Virtuozzo =====
 +
 +Il software di virtualizzazione [[wp>Virtuozzo]] viene utilizzato da alcuni provider di VPS. Si tratta di software **non libero**.
 +
 +==== Limite  regole iptables ====
 +
 +La piattaforma di virtualizzazione pone dei limiti sul numero di regole netfilter che si possono attivare. Per vedere il limite attuale:
 +
 +<code>
 +cat /proc/user_beancounters
 +</code>
 +
 +Vedere il valore //barrier// e //limit// di **numiptent**. Solo l'amministratore Virtuozzo può modificare tale limite.
 +
 +L'errore che si può verificare - ad esempio avviando il firewall Shorewall - è:
 +
 +<code>
 +iptables-restore: line 129 failed
 +</code>
 +
 +===== Virtualbox =====
 +
 +Prove fatte su Ubuntu 11.10. Si installa il pacchetto **''linux-headers-*''** relativo alla versione kernel in uso (**''uname -a''**) e il pacchetto con i sorgenti del modulo kernel **''virtualbox-dkms''**. Al termine dell'installazione dei sorgenti il modulo kernel dovrebbe risultare compilato e installato:
 +
 +<code>
 +find /lib/modules/ | grep vboxdrv
 +/lib/modules/3.0.0-30-generic-pae/updates/dkms/vboxdrv.ko
 +/lib/modules/3.0.0-32-generic-pae/updates/dkms/vboxdrv.ko
 +</code>
 +
 +In caso di aggiornamento del kernel bisogna ricordarsi di installare anche il pacchetto **''linux-headers-*''** relativo, e tutto dovrebbe funzionare automaticamente.
doc/appunti/linux/sa/virtualization.txt · Last modified: 2019/08/28 12:09 by niccolo