Failed lxd init. what is CIDR?

What IPv4 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]: 10.1.1.0/24
Invalid input: Not a usable IPv4 address: 10.1.1.0/24

What IPv4 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]: 10.1.1.0/255.255.255.0
Invalid input: invalid CIDR address: 10.1.1.0/255.255.255.0

so,what is CIDR?

The format you have used is correct CIDR format, but the value is not a valid IP address.

The value you have specified is the “network address”, i.e “.0” is the network address of the subnet “10.1.1.0/24”. Instead you need to specify an IP in that network, such as “.1”, e.g. “10.1.1.1/24”