ss / netstat Error Messages
Inspect sockets and listening ports.All ss / netstat pages
- bash: ss: command not foundss is part of the Linux iproute2 package, missing in slim containers and absent on macOS. Install iproute2 (iproute on Fedora/RHEL) or use lsof and netstat.
- ss: "ipv4" is invalid familyss -f accepts inet, inet6, link, unix, netlink, vsock, tipc and xdp, not ipv4 or tcp. Use -f inet or -4 for IPv4, and -t or -u to pick TCP or UDP sockets.
- ss: bison bellows (while parsing filter): "syntax error!"ss could not parse its filter: an incomplete condition, unbalanced parentheses or a bad operator. Quote the filter, for example ss -tn '( dport = :443 )'.
- ss: wrong state name: listenss state filters use lowercase hyphenated names: listening, not listen; time-wait, not TIME_WAIT. Use ss -l for listening sockets. ss exits with status 255.