Support for User Mode Linux in libvirt[1] may be of interest to people on this list.
Regards, Daniel [1] http://libvirt.org/ ----- Forwarded message from "Daniel P. Berrange" <[EMAIL PROTECTED]> ----- > Date: Thu, 16 Oct 2008 12:42:17 +0100 > From: "Daniel P. Berrange" <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED] > Subject: [libvirt] PATCH: Experimental User Mode Linux driver for libvirt > > This patch implements a driver supporting User Mode Linux guests. User mode > linux is a kind of paravirtualized kernel which runs on a plain Linux host. > It requires no elevated privileges at all, except for some of the network > integration. It is a pretty straightforward thing to invoke, so I figured > it would be easy to write a driver to support it. I was right :-) > > As with the QEMU driver, there are two styles of invocation > > uml:///system - a single privileged, per host driver instance as root > uml:///session - a per-user unprivileged instance > > The user mode linux docs recommend against running as root, so naturally > I recommend use of uml:///session, though my testing is so far with > uml:///system. > > It supports the bare minimum neccessary for a libvirt driver, namely start, > stop, define, create, destroy, undefine against domains. For configuration > it supports setting of memory limit, virtual disk devices, and paravirt > console devices - good enough to get 'virsh console' working over a PTY, > and dump XML config. > > Like QEMU, UML has an admin monitor console. It is a little different > though, using a UNIX domain socket, in datagram mode, sending command > strings back & forth. This actaully makes it a little easier to deal > with in libvirt. User mode linux has a uml_mconsole command line tool > to interact with it, but I directly implement the socket support in > libvirt instead, so this driver does not (yet) have any dependancy on > the UML utilities. > > The driver is largely a clone of the QEMU driver, replacing the bit which > builds the command line argv, and all code dealing with the QEMU monitor. > Since the monitor socket is datagram based, we can't make use of it for > detecting VM shutdown as we do with QEMU/LXC. So instead, I make use of > inotify, to monitor $HOME/.uml which is populated witha directory for > each VM. When we see a directory created, libvirt marks the corresponding > VM as running, finds it PID & probes the monitor for the PTY config. When > we see a directory deleted, libvirt makes the VM as shutoff and frees any > resources its holding. This actually works very nicely & simply. > > An example config I'm using for testing is > > <domain type='uml'> > <name>demo</name> > <uuid>b4433fc2-a22e-ffb3-0a3d-9c173b395800</uuid> > <memory>500000</memory> > <os> > <type arch='x86_64'>uml</type> > <kernel>/home/berrange/linux</kernel> > </os> > <devices> > <disk type='file' device='disk'> > <source file='/home/berrange/FedoraCore6-AMD64-root_fs'/> > <target dev='ubd0' bus='uml'/> > </disk> > <console type='pty'> > <target port='0'/> > </console> > <serial type='tcp'> > <source mode='bind' host='localhost' service='9000'/> > <target port='0'/> > </serial> > <serial type='pty'> > <target port='3'/> > </serial> > </devices> > </domain> > > The user mode linux kernel, has the device emulator built-in, so there's no > need to specify the device emulator path explicitly. The kernel I built > straight from latest 2.6.27 sources, and the root filesystem I downloaded > from the UML website. I've been testing with latest libvirt CVS, on a > Fedora 9 x86_64 host. > > If you save that config to a file 'demo.xml', you ought to be able todo > > virsh --connect uml:///system define demo.xml > virsh --connect uml:///system start demo > virsh --connect uml:///system console demo > > Though there is still a small race whereby we can ask for the PTY device > before its been created, causing console to fail. > > If things go wrong /var/log/libvirt/uml/$NAME.log contains log messages, > The configuration is stored in /etc/libvirt/uml/$NAME.xml, or in > $HOME/.libvirt/uml/$NAME.xml, and you can also query stuff with mconsole > by doing 'uml_mconsole $NAME' > > This isn't quite ready to merge, but I thought I'd send it here to make > people aware of it. > > configure.in | 8 > include/libvirt/virterror.h | 1 > src/Makefile.am | 9 > src/domain_conf.c | 47 - > src/domain_conf.h | 1 > src/driver.h | 3 > src/libvirt.c | 6 > src/qemu_conf.c | 3 > src/remote_internal.c | 16 > src/uml_conf.c | 404 ++++++++++ > src/uml_conf.h | 72 + > src/uml_driver.c | 1771 > ++++++++++++++++++++++++++++++++++++++++++++ > src/uml_driver.h | 34 > src/virterror.c | 4 > 14 files changed, 2355 insertions(+), 24 deletions(-) > > > Daniel ----- End forwarded message ----- -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
