I created a set of ips: #!/bin/bash NFT=/usr/sbin/nft $NFT add set inet filter ALLOWIPS { type ipv4_addr \; flags constant, interval \; }. $NFT flush set inet filter ALLOWIPS $NFT add element inet filter ALLOWIPS { 172.17.0.0/24 } $NFT add element inet filter ALLOWIPS { 192.168.0.0/24 } $NFT add element inet filter ALLOWIPS { 192.168.1.58 } $NFT add element inet filter ALLOWIPS { 192.168.1.89 } $NFT add element inet filter ALLOWIPS { 192.168.1.125 } $NFT add element inet filter ALLOWIPS { 192.168.1.179 } $NFT add element inet filter ALLOWIPS { 192.168.1.212 } Then I use this set # nft add rule inet filter input iifname int1 ip daddr 8.8.8.8 ip saddr @ALLOWIPS accept But when I try to remove / add ips I get: # nft add element inet filter ALLOWIPS { 192.168.1.58 } Error: Could not process rule: Device or resource busy add element inet filter ALLOWIPS { 192.168.1.58 } ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ # nft flush set inet filter ALLOWIPS Error: Could not process rule: Device or resource busy flush set inet filter ALLOWIPS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Why?