On a Saturday in 2025, Chimmie Firefly via Users wrote:

Hello,

Hello.

I have an issue whenever using `/proc/sys/ipv6/conf` as read-only mountpoint.

May I ask why? Essentially you're asking libvirt to both manage and not manage your network :)

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

The code dealing with this expects `disable_ipv6` to be writable if it exists, same with `accept_ra` and `autoconf`

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?

In general, no. And it also does not seem possible in this particular case. Jano