KVM/libvirt

libvirt is a virtualization API with supports for KVM, QEMU, Xen, Virtuozzo, VMWare ESX, LXC, BHyve and more

Ubuntu packages

At least the following packages compose libvirt in Ubuntu:

• libvirt-bin
• libvirt-clients: virsh, virt-admin virt-host-validate virt-login-shell virt-pki-validate virt-xml-validate
• libvirt-daemon:

libvirtd: /etc/libvirt/virtlogd.conf

virt-sanlock-cleanup

virtlockd

virtlogd

Config files and directories

• Config directories:

/etc/libvirt/

/etc/libvirt/qemu

• Config files:

/etc/libvirt/virtlogd.conf

Includes information about Unix Socket permissions: unix_sock_group, unix_sock_ro_perms, unix_sock_rw_perms, auth_unix_ro, auth_unix_rw

• Images directory: /var/lib/libvirt/images (See: virsh pool-define-as)
• Logs:

/var/log/libvirt/qemu

journalctl -u libvirtd

Journalctl errors

libvirtd[14189]: 2019-11-21 15:08:13.035+0000: 14192: error : qemuDomainBlockCommit:17568 : invalid argument: top '/path/to/file/VM_NAME.qcow2' in chain for 'hda' has no backing file

Activities

Basic

• Read Libvirt Changelog: https://libvirt.org/git/?p=libvirt.git;a=log
• Read Libvirt Release notes: https://libvirt.org/news.html
• Read Libvirt FAQ: https://wiki.libvirt.org/page/FAQ

Medium

• Restart libvirtd daemon: systemctl restart libvirtd

Expert:

• Read Libvirt code: https://github.com/libvirt/libvirt
• Implement uptime functionality in libvirt code: https://www.spinics.net/linux/fedora/libvir/msg98027.html
• Review libvirt error messages in journald
• Understand different CPU model an topologies: https://libvirt.org/formatdomain.html#elementsCPU

See also

• virsh command line utility
• qemu
• MacVTap