How to disable sysctl calls performed by libvirt?
Hello,
I have an issue whenever using `/proc/sys/ipv6/conf` as read-only mountpoint.
While the libvirt by itself is running fine, I'm unable to create NAT network
interfaces because of the following error:
```
2025-07-05 19:33:32.821+0000: 100: error : networkSetIPv6Sysctl:1847 : cannot write to
'/proc/sys/net/ipv6/conf/virbr0/disable_ipv6' on bridge 'virbr0':
Read-only file system
2025-07-05 19:33:32.841+0000: 100: error : virNetDevSetIFFlag:601 : Cannot get interface
flags on 'virbr0': No such device
2025-07-05 19:33:32.947+0000: 100: error : virNetlinkDelLink:688 : error destroying
network device virbr0: No such device
```
While using iproute2 and bridge utils, I'm able to create and configure new bridge
device, along with attaching the VM to the interface.
I've used the following commands:
```
sysctl -w net.ipv4.ip_forward=1
brctl addbr br0
ip link set br0 up
ip addr add 192.168.100.1/24 dev br0
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i br0 -o eth0 -j ACCEPT
iptables -A FORWARD -i eth0 -o br0 -m state --state RELATED,ESTABLISHED -j ACCEPT
```
Is libvirt allowing to disable sysctl calls in the configuration files? If so, what should
I set in the config?