https://wiki.archlinux.org/index.php/Libvirt#Networks is a better starting point (make sure to follow the links in that section, especially the first and 2nd link)..
If you want to continue with your current approach :
failed to communicate with bridge helper: Transport endpoint is not connected
stderr=failed to parse default acl file `/etc/qemu/bridge.conf'
Check your /etc/qemu/bridge.conf file .
]]>Error message in QEMU/KVM User session:
Error starting domain: internal error: /usr/lib/qemu/qemu-bridge-helper --use-vnet --br=br1 --fd=29: failed to communicate with bridge helper: Transport endpoint is not connected
stderr=failed to parse default acl file `/etc/qemu/bridge.conf'
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 65, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 101, in tmpcb
callback(*args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/libvirtobject.py", line 57, in newfn
ret = fn(self, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/domain.py", line 1329, in startup
self._backend.create()
File "/usr/lib/python3.9/site-packages/libvirt.py", line 1234, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirt.libvirtError: internal error: /usr/lib/qemu/qemu-bridge-helper --use-vnet --br=br1 --fd=29: failed to communicate with bridge helper: Transport endpoint is not connected
stderr=failed to parse default acl file `/etc/qemu/bridge.conf'
Error message in QEMU/KVM session (system wide):
Error starting domain: Cannot get interface MTU on 'br1': No such device
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 65, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 101, in tmpcb
callback(*args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/libvirtobject.py", line 57, in newfn
ret = fn(self, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/domain.py", line 1329, in startup
self._backend.create()
File "/usr/lib/python3.9/site-packages/libvirt.py", line 1234, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirt.libvirtError: Cannot get interface MTU on 'br1': No such device
What am I missing? DE is GNOME. ebtables, dnsmasq and bridge-utils are installed. libvirtd.service is running without errors. My user is a member of the libvirt group.
]]>