[libvirt] enumerating disk devices
Hi,
Some people appear to have autostart VMs residing on slow storage. If
libvirtd starts too early, it'll simply fail trying to start those VMs.
It'd be nice to know when all the storage on which autostart containers
depend becomes available, so as to safely start libvirt.
The python script appended below is one approach. It could be called as
something like
for f in /etc/libvirt/qemu/autostart/* /etc/libvirt/lxc/autostart/*; do
for d in `libvirt_list_storage.py $f`; do
if [ ! -r $d ]; then
echo "storage not yet ready"
exit 1
fi
done
done
echo "starting libvirtd"
libvirtd
(Realistically I would have this running in an upstart job which is
'start on mounted' and, if all storage available, emits a
'libvirt-storage-up' event).
Are there better ways to go about this?
thanks,
-serge
#!/usr/bin/python
import sys
from xml.dom.minidom import parse
dom = parse(sys.argv[1])
def getText(nodelist):
rc = []
for node in nodelist:
if node.nodeType == node.TEXT_NODE:
rc.append(node.data)
return ''.join(rc)
def print_domname(dom):
#return
print "Domain %s\n" % getText(dom.childNodes)
def liststorages(dom):
print_domname(dom.getElementsByTagName("name")[0])
disks = dom.getElementsByTagName("disk")
list_disks(disks)
filesystems = dom.getElementsByTagName('filesystem')
list_filesystems(filesystems)
def list_filesystems(fslist):
for fs in fslist:
if not fs.hasAttribute('type'):
continue
if fs.getAttribute('type') != 'mount':
continue
dirs = fs.getElementsByTagName("source")
if len(dirs) == 0:
continue
if not dirs[0].getAttribute('dir'):
continue
print "dir: %s\n" % dirs[0].getAttribute('dir')
def list_disks(disks):
for disk in disks:
if not disk.hasAttribute('type'):
continue
if disk.getAttribute('type') == 'file':
list_disk_type_file(disk)
elif disk.getAttribute('type') == 'block':
list_disk_type_block(disk)
else:
# not supported
continue
def list_disk_type_file(disk):
disksrcs = disk.getElementsByTagName("source")
if len(disksrcs) == 0:
return
if not disksrcs[0].hasAttribute('file'):
return
print "file: %s\n" % disksrcs[0].getAttribute('file')
def list_disk_type_block(disk):
devsrscs = disk.getElementsByTagName("source")
if len(devsrscs) == 0:
return
if not devsrscs[0].hasAttribute('dev'):
return
print "dev: %s\n" % devsrscs[0].getAttribute('dev')
liststorages(dom)