{ "mode": "man", "parameter": "ss", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ss/8/json", "generated": "2026-06-05T21:10:45Z", "synopsis": "ss [options] [ FILTER ]", "sections": { "NAME": { "content": "ss - another utility to investigate sockets\n", "subsections": [] }, "SYNOPSIS": { "content": "ss [options] [ FILTER ]\n", "subsections": [] }, "DESCRIPTION": { "content": "ss is used to dump socket statistics. It allows showing information similar to netstat. It\ncan display more TCP and state information than other tools.\n\n", "subsections": [] }, "OPTIONS": { "content": "When no option is used ss displays a list of open non-listening sockets (e.g. TCP/UNIX/UDP)\nthat have established connection.\n", "subsections": [ { "name": "-h, --help", "content": "Show summary of options.\n", "flag": "-h", "long": "--help" }, { "name": "-V, --version", "content": "Output version information.\n", "flag": "-V", "long": "--version" }, { "name": "-H, --no-header", "content": "Suppress header line.\n", "flag": "-H", "long": "--no-header" }, { "name": "-O, --oneline", "content": "Print each socket's data on a single line.\n", "flag": "-O", "long": "--oneline" }, { "name": "-n, --numeric", "content": "Do not try to resolve service names. Show exact bandwidth values, instead of human-\nreadable.\n", "flag": "-n", "long": "--numeric" }, { "name": "-r, --resolve", "content": "Try to resolve numeric address/ports.\n", "flag": "-r", "long": "--resolve" }, { "name": "-a, --all", "content": "Display both listening and non-listening (for TCP this means established connections)\nsockets.\n", "flag": "-a", "long": "--all" }, { "name": "-l, --listening", "content": "Display only listening sockets (these are omitted by default).\n", "flag": "-l", "long": "--listening" }, { "name": "-o, --options", "content": "Show timer information. For TCP protocol, the output format is:\n\ntimer:(,,)\n\n\nthe name of the timer, there are five kind of timer names:\n\non : means one of these timers: TCP retrans timer, TCP early retrans timer and\ntail loss probe timer\n\nkeepalive: tcp keep alive timer\n\ntimewait: timewait stage timer\n\npersist: zero window probe timer\n\nunknown: none of the above timers\n\n\nhow long time the timer will expire\n\n\nhow many times the retransmission occurred\n", "flag": "-o", "long": "--options" }, { "name": "-e, --extended", "content": "Show detailed socket information. The output format is:\n\nuid: ino: sk:\n\n\nthe user id the socket belongs to\n\n\nthe socket's inode number in VFS\n\n\nan uuid of the socket\n", "flag": "-e", "long": "--extended" }, { "name": "-m, --memory", "content": "Show socket memory usage. The output format is:\n\nskmem:(r,rb,t,tb,\nf,w,o,\nbl,d)\n\n\nthe memory allocated for receiving packet\n\n\nthe total memory can be allocated for receiving packet\n\n\nthe memory used for sending packet (which has been sent to layer 3)\n\n\nthe total memory can be allocated for sending packet\n\n\nthe memory allocated by the socket as cache, but not used for receiving/sending\npacket yet. If need memory to send/receive packet, the memory in this cache\nwill be used before allocate additional memory.\n\n\nThe memory allocated for sending packet (which has not been sent to layer 3)\n\n\nThe memory used for storing socket option, e.g., the key for TCP MD5 signature\n\n\nThe memory used for the sk backlog queue. On a process context, if the process\nis receiving packet, and a new packet is received, it will be put into the sk\nbacklog queue, so it can be received by the process immediately\n\n\nthe number of packets dropped before they are de-multiplexed into the socket\n", "flag": "-m", "long": "--memory" }, { "name": "-p, --processes", "content": "Show process using socket.\n", "flag": "-p", "long": "--processes" }, { "name": "-i, --info", "content": "Show internal TCP information. Below fields may appear:\n\nts show string \"ts\" if the timestamp option is set\n\nsack show string \"sack\" if the sack option is set\n\necn show string \"ecn\" if the explicit congestion notification option is set\n\necnseen\nshow string \"ecnseen\" if the saw ecn flag is found in received packets\n\nfastopen\nshow string \"fastopen\" if the fastopen option is set\n\ncongalg\nthe congestion algorithm name, the default congestion algorithm is \"cubic\"\n\nwscale::\nif window scale option is used, this field shows the send scale factor and re‐\nceive scale factor\n\nrto:\ntcp re-transmission timeout value, the unit is millisecond\n\nbackoff:\nused for exponential backoff re-transmission, the actual re-transmission time‐\nout value is icskrto << icskbackoff\n\nrtt:/\nrtt is the average round trip time, rttvar is the mean deviation of rtt, their\nunits are millisecond\n\nato:\nack timeout, unit is millisecond, used for delay ack mode\n\nmss:\nmax segment size\n\ncwnd:\ncongestion window size\n\npmtu:\npath MTU value\n\nssthresh:\ntcp congestion window slow start threshold\n\nbytesacked:\nbytes acked\n\nbytesreceived:\nbytes received\n\nsegsout:\nsegments sent out\n\nsegsin:\nsegments received\n\nsend bps\negress bps\n\nlastsnd:\nhow long time since the last packet sent, the unit is millisecond\n\nlastrcv:\nhow long time since the last packet received, the unit is millisecond\n\nlastack:\nhow long time since the last ack received, the unit is millisecond\n\npacingrate bps/bps\nthe pacing rate and max pacing rate\n\nrcvspace:\na helper variable for TCP internal auto tuning socket receive buffer\n\ntcp-ulp-mptcp flags:[MmBbJjecv] token: seq:\nsfseq: ssnoff: maplen:\nMPTCP subflow information\n\n--tos Show ToS and priority information. Below fields may appear:\n\ntos IPv4 Type-of-Service byte\n\ntclass IPv6 Traffic Class byte\n\nclassid\nClass id set by netcls cgroup. If class is zero this shows priority set by\nSOPRIORITY.\n", "flag": "-i", "long": "--info" }, { "name": "--cgroup", "content": "Show cgroup information. Below fields may appear:\n\ncgroup Cgroup v2 pathname. This pathname is relative to the mount point of the hierar‐\nchy.\n", "long": "--cgroup" }, { "name": "-K, --kill", "content": "Attempts to forcibly close sockets. This option displays sockets that are successfully\nclosed and silently skips sockets that the kernel does not support closing. It sup‐\nports IPv4 and IPv6 sockets only.\n", "flag": "-K", "long": "--kill" }, { "name": "-s, --summary", "content": "Print summary statistics. This option does not parse socket lists obtaining summary\nfrom various sources. It is useful when amount of sockets is so huge that parsing\n/proc/net/tcp is painful.\n", "flag": "-s", "long": "--summary" }, { "name": "-E, --events", "content": "Continually display sockets as they are destroyed\n", "flag": "-E", "long": "--events" }, { "name": "-Z, --context", "content": "As the -p option but also shows process security context.\n\nFor netlink(7) sockets the initiating process context is displayed as follows:\n\n1. If valid pid show the process context.\n\n2. If destination is kernel (pid = 0) show kernel initial context.\n\n3. If a unique identifier has been allocated by the kernel or netlink user,\nshow context as \"unavailable\". This will generally indicate that a process\nhas more than one netlink socket active.\n", "flag": "-Z", "long": "--context" }, { "name": "-z, --contexts", "content": "As the -Z option but also shows the socket context. The socket context is taken from\nthe associated inode and is not the actual socket context held by the kernel. Sockets\nare typically labeled with the context of the creating process, however the context\nshown will reflect any policy role, type and/or range transition rules applied, and is\ntherefore a useful reference.\n", "flag": "-z", "long": "--contexts" }, { "name": "-N NSNAME, --net=NSNAME", "content": "Switch to the specified network namespace name.\n", "flag": "-N", "long": "--net", "arg": "NSNAME" }, { "name": "-b, --bpf", "content": "Show socket classic BPF filters (only administrators are allowed to get these informa‐\ntion).\n", "flag": "-b", "long": "--bpf" }, { "name": "-4, --ipv4", "content": "Display only IP version 4 sockets (alias for -f inet).\n", "flag": "-4", "long": "--ipv4" }, { "name": "-6, --ipv6", "content": "Display only IP version 6 sockets (alias for -f inet6).\n", "flag": "-6", "long": "--ipv6" }, { "name": "-0, --packet", "content": "Display PACKET sockets (alias for -f link).\n", "flag": "-0", "long": "--packet" }, { "name": "-t, --tcp", "content": "Display TCP sockets.\n", "flag": "-t", "long": "--tcp" }, { "name": "-u, --udp", "content": "Display UDP sockets.\n", "flag": "-u", "long": "--udp" }, { "name": "-d, --dccp", "content": "Display DCCP sockets.\n", "flag": "-d", "long": "--dccp" }, { "name": "-w, --raw", "content": "Display RAW sockets.\n", "flag": "-w", "long": "--raw" }, { "name": "-x, --unix", "content": "Display Unix domain sockets (alias for -f unix).\n", "flag": "-x", "long": "--unix" }, { "name": "-S, --sctp", "content": "Display SCTP sockets.\n", "flag": "-S", "long": "--sctp" }, { "name": "--vsock", "content": "Display vsock sockets (alias for -f vsock).\n\n--xdp Display XDP sockets (alias for -f xdp).\n", "long": "--vsock" }, { "name": "--inet-sockopt", "content": "Display inet socket options.\n", "long": "--inet-sockopt" }, { "name": "-f FAMILY, --family=FAMILY", "content": "Display sockets of type FAMILY. Currently the following families are supported: unix,\ninet, inet6, link, netlink, vsock, xdp.\n", "flag": "-f", "long": "--family", "arg": "FAMILY" }, { "name": "-A QUERY, --query=QUERY, --socket=QUERY", "content": "List of socket tables to dump, separated by commas. The following identifiers are un‐\nderstood: all, inet, tcp, udp, raw, unix, packet, netlink, unixdgram, unixstream,\nunixseqpacket, packetraw, packetdgram, dccp, sctp, vsockstream, vsockdgram, xdp\nAny item in the list may optionally be prefixed by an exclamation mark (!) to exclude\nthat socket table from being dumped.\n", "flag": "-A", "long": "--socket", "arg": "QUERY" }, { "name": "-D FILE, --diag=FILE", "content": "Do not display anything, just dump raw information about TCP sockets to FILE after ap‐\nplying filters. If FILE is - stdout is used.\n", "flag": "-D", "long": "--diag", "arg": "FILE" }, { "name": "-F FILE, --filter=FILE", "content": "Read filter information from FILE. Each line of FILE is interpreted like single com‐\nmand line option. If FILE is - stdin is used.\n", "flag": "-F", "long": "--filter", "arg": "FILE" }, { "name": "FILTER := [ state STATE-FILTER ] [ EXPRESSION ]", "content": "Please take a look at the official documentation for details regarding filters.\n\n" } ] }, "STATE-FILTER": { "content": "STATE-FILTER allows to construct arbitrary set of states to match. Its syntax is sequence of\nkeywords state and exclude followed by identifier of state.\n\nAvailable identifiers are:\n\nAll standard TCP states: established, syn-sent, syn-recv, fin-wait-1, fin-wait-2,\ntime-wait, closed, close-wait, last-ack, listening and closing.\n\nall - for all the states\n\nconnected - all the states except for listening and closed\n\nsynchronized - all the connected states except for syn-sent\n\nbucket - states, which are maintained as minisockets, i.e. time-wait and syn-recv\n\nbig - opposite to bucket\n\n", "subsections": [] }, "EXPRESSION": { "content": "EXPRESSION allows filtering based on specific criteria. EXPRESSION consists of a series of\npredicates combined by boolean operators. The possible operators in increasing order of\nprecedence are or (or | or ||), and (or & or &&), and not (or !). If no operator is between\nconsecutive predicates, an implicit and operator is assumed. Subexpressions can be grouped\nwith \"(\" and \")\".\n\nThe following predicates are supported:\n\n", "subsections": [ { "name": "{dst|src} [=] HOST", "content": "Test if the destination or source matches HOST. See HOST SYNTAX for details.\n" }, { "name": "{dport|sport} [OP] [FAMILY:]:PORT", "content": "Compare the destination or source port to PORT. OP can be any of \"<\", \"<=\", \"=\", \"!=\",\n\">=\" and \">\". Following normal arithmetic rules. FAMILY and PORT are as described in\nHOST SYNTAX below.\n" }, { "name": "dev [=|!=] DEVICE", "content": "Match based on the device the connection uses. DEVICE can either be a device name or\nthe index of the interface.\n" }, { "name": "fwmark [=|!=] MASK", "content": "Matches based on the fwmark value for the connection. This can either be a specific\nmark value or a mark value followed by a \"/\" and a bitmask of which bits to use in the\ncomparison. For example \"fwmark = 0x01/0x03\" would match if the two least significant\nbits of the fwmark were 0x01.\n" }, { "name": "cgroup [=|!=] PATH", "content": "Match if the connection is part of a cgroup at the given path.\n" }, { "name": "autobound", "content": "Match if the port or path of the source address was automatically allocated (rather\nthan explicitly specified).\n\nMost operators have aliases. If no operator is supplied \"=\" is assumed. Each of the follow‐\ning groups of operators are all equivalent:\n\n• = == eq\n\n• != ne neq\n\n• > gt\n\n• < lt\n\n• >= ge geq\n\n• <= le leq\n\n• ! not\n\n• | || or\n\n• & && and\n" } ] }, "HOST SYNTAX": { "content": "The general host syntax is [FAMILY:]ADDRESS[:PORT].\n\nFAMILY must be one of the families supported by the -f option. If not given it defaults to\nthe family given with the -f option, and if that is also missing, will assume either inet or\ninet6. Note that all host conditions in the expression should either all be the same family\nor be only inet and inet6. If there is some other mixture of families, the results will prob‐\nably be unexpected.\n\nThe form of ADDRESS and PORT depends on the family used. \"*\" can be used as a wildcard for\neither the address or port. The details for each family are as follows:\n\nunix ADDRESS is a glob pattern (see fnmatch(3)) that will be matched case-insensitively\nagainst the unix socket's address. Both path and abstract names are supported. Unix\naddresses do not support a port, and \"*\" cannot be used as a wildcard.\n\nlink ADDRESS is the case-insensitive name of an Ethernet protocol to match. PORT is either\na device name or a device index for the desired link device, as seen in the output of\nip link.\n", "subsections": [ { "name": "netlink", "content": "ADDRESS is a descriptor of the netlink family. Possible values come from\n/etc/iproute2/nlprotos. PORT is the port id of the socket, which is usually the same\nas the owning process id. The value \"kernel\" can be used to represent the kernel (port\nid of 0).\n\nvsock ADDRESS is an integer representing the CID address, and PORT is the port.\n\ninet and inet6\nADDRESS is an ip address (either v4 or v6 depending on the family) or a DNS hostname\nthat resolves to an ip address of the required version. An ipv6 address must be en‐\nclosed in \"[\" and \"]\" to disambiguate the port separator. The address may additionally\nhave a prefix length given in CIDR notation (a slash followed by the prefix length in\nbits). PORT is either the numerical socket port, or the service name for the port to\nmatch.\n\n" } ] }, "USAGE EXAMPLES": { "content": "", "subsections": [ { "name": "ss -t -a", "content": "Display all TCP sockets.\n" }, { "name": "ss -t -a -Z", "content": "Display all TCP sockets with process SELinux security contexts.\n" }, { "name": "ss -u -a", "content": "Display all UDP sockets.\n" }, { "name": "ss -o state established '( dport = :ssh or sport = :ssh )'", "content": "Display all established ssh connections.\n\nss -x src /tmp/.X11-unix/*\nFind all local processes connected to X server.\n" }, { "name": "ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24", "content": "List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24\nand look at their timers.\n" }, { "name": "ss -a -A 'all,!tcp'", "content": "List sockets in all states from all socket tables but TCP.\n" } ] }, "SEE ALSO": { "content": "ip(8),\nRFC 793 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)\n\n", "subsections": [] }, "AUTHOR": { "content": "ss was written by Alexey Kuznetsov, .\n\nThis manual page was written by Michael Prokop for the Debian project (but\nmay be used by others).\n\n\n\nSS(8)", "subsections": [] } }, "summary": "ss - another utility to investigate sockets", "flags": [ { "flag": "-h", "long": "--help", "arg": null, "description": "Show summary of options." }, { "flag": "-V", "long": "--version", "arg": null, "description": "Output version information." }, { "flag": "-H", "long": "--no-header", "arg": null, "description": "Suppress header line." }, { "flag": "-O", "long": "--oneline", "arg": null, "description": "Print each socket's data on a single line." }, { "flag": "-n", "long": "--numeric", "arg": null, "description": "Do not try to resolve service names. Show exact bandwidth values, instead of human- readable." }, { "flag": "-r", "long": "--resolve", "arg": null, "description": "Try to resolve numeric address/ports." }, { "flag": "-a", "long": "--all", "arg": null, "description": "Display both listening and non-listening (for TCP this means established connections) sockets." }, { "flag": "-l", "long": "--listening", "arg": null, "description": "Display only listening sockets (these are omitted by default)." }, { "flag": "-o", "long": "--options", "arg": null, "description": "Show timer information. For TCP protocol, the output format is: timer:(,,) the name of the timer, there are five kind of timer names: on : means one of these timers: TCP retrans timer, TCP early retrans timer and tail loss probe timer keepalive: tcp keep alive timer timewait: timewait stage timer persist: zero window probe timer unknown: none of the above timers how long time the timer will expire how many times the retransmission occurred" }, { "flag": "-e", "long": "--extended", "arg": null, "description": "Show detailed socket information. The output format is: uid: ino: sk: the user id the socket belongs to the socket's inode number in VFS an uuid of the socket" }, { "flag": "-m", "long": "--memory", "arg": null, "description": "Show socket memory usage. The output format is: skmem:(r,rb,t,tb, f,w,o, bl,d) the memory allocated for receiving packet the total memory can be allocated for receiving packet the memory used for sending packet (which has been sent to layer 3) the total memory can be allocated for sending packet the memory allocated by the socket as cache, but not used for receiving/sending packet yet. If need memory to send/receive packet, the memory in this cache will be used before allocate additional memory. The memory allocated for sending packet (which has not been sent to layer 3) The memory used for storing socket option, e.g., the key for TCP MD5 signature The memory used for the sk backlog queue. On a process context, if the process is receiving packet, and a new packet is received, it will be put into the sk backlog queue, so it can be received by the process immediately the number of packets dropped before they are de-multiplexed into the socket" }, { "flag": "-p", "long": "--processes", "arg": null, "description": "Show process using socket." }, { "flag": "-i", "long": "--info", "arg": null, "description": "Show internal TCP information. Below fields may appear: ts show string \"ts\" if the timestamp option is set sack show string \"sack\" if the sack option is set ecn show string \"ecn\" if the explicit congestion notification option is set ecnseen show string \"ecnseen\" if the saw ecn flag is found in received packets fastopen show string \"fastopen\" if the fastopen option is set congalg the congestion algorithm name, the default congestion algorithm is \"cubic\" wscale:: if window scale option is used, this field shows the send scale factor and re‐ ceive scale factor rto: tcp re-transmission timeout value, the unit is millisecond backoff: used for exponential backoff re-transmission, the actual re-transmission time‐ out value is icskrto << icskbackoff rtt:/ rtt is the average round trip time, rttvar is the mean deviation of rtt, their units are millisecond ato: ack timeout, unit is millisecond, used for delay ack mode mss: max segment size cwnd: congestion window size pmtu: path MTU value ssthresh: tcp congestion window slow start threshold bytesacked: bytes acked bytesreceived: bytes received segsout: segments sent out segsin: segments received send bps egress bps lastsnd: how long time since the last packet sent, the unit is millisecond lastrcv: how long time since the last packet received, the unit is millisecond lastack: how long time since the last ack received, the unit is millisecond pacingrate bps/bps the pacing rate and max pacing rate rcvspace: a helper variable for TCP internal auto tuning socket receive buffer tcp-ulp-mptcp flags:[MmBbJjecv] token: seq: sfseq: ssnoff: maplen: MPTCP subflow information --tos Show ToS and priority information. Below fields may appear: tos IPv4 Type-of-Service byte tclass IPv6 Traffic Class byte classid Class id set by netcls cgroup. If class is zero this shows priority set by SOPRIORITY." }, { "flag": "", "long": "--cgroup", "arg": null, "description": "Show cgroup information. Below fields may appear: cgroup Cgroup v2 pathname. This pathname is relative to the mount point of the hierar‐ chy." }, { "flag": "-K", "long": "--kill", "arg": null, "description": "Attempts to forcibly close sockets. This option displays sockets that are successfully closed and silently skips sockets that the kernel does not support closing. It sup‐ ports IPv4 and IPv6 sockets only." }, { "flag": "-s", "long": "--summary", "arg": null, "description": "Print summary statistics. This option does not parse socket lists obtaining summary from various sources. It is useful when amount of sockets is so huge that parsing /proc/net/tcp is painful." }, { "flag": "-E", "long": "--events", "arg": null, "description": "Continually display sockets as they are destroyed" }, { "flag": "-Z", "long": "--context", "arg": null, "description": "As the -p option but also shows process security context. For netlink(7) sockets the initiating process context is displayed as follows: 1. If valid pid show the process context. 2. If destination is kernel (pid = 0) show kernel initial context. 3. If a unique identifier has been allocated by the kernel or netlink user, show context as \"unavailable\". This will generally indicate that a process has more than one netlink socket active." }, { "flag": "-z", "long": "--contexts", "arg": null, "description": "As the -Z option but also shows the socket context. The socket context is taken from the associated inode and is not the actual socket context held by the kernel. Sockets are typically labeled with the context of the creating process, however the context shown will reflect any policy role, type and/or range transition rules applied, and is therefore a useful reference." }, { "flag": "-N", "long": "--net", "arg": "NSNAME", "description": "Switch to the specified network namespace name." }, { "flag": "-b", "long": "--bpf", "arg": null, "description": "Show socket classic BPF filters (only administrators are allowed to get these informa‐ tion)." }, { "flag": "-4", "long": "--ipv4", "arg": null, "description": "Display only IP version 4 sockets (alias for -f inet)." }, { "flag": "-6", "long": "--ipv6", "arg": null, "description": "Display only IP version 6 sockets (alias for -f inet6)." }, { "flag": "-0", "long": "--packet", "arg": null, "description": "Display PACKET sockets (alias for -f link)." }, { "flag": "-t", "long": "--tcp", "arg": null, "description": "Display TCP sockets." }, { "flag": "-u", "long": "--udp", "arg": null, "description": "Display UDP sockets." }, { "flag": "-d", "long": "--dccp", "arg": null, "description": "Display DCCP sockets." }, { "flag": "-w", "long": "--raw", "arg": null, "description": "Display RAW sockets." }, { "flag": "-x", "long": "--unix", "arg": null, "description": "Display Unix domain sockets (alias for -f unix)." }, { "flag": "-S", "long": "--sctp", "arg": null, "description": "Display SCTP sockets." }, { "flag": "", "long": "--vsock", "arg": null, "description": "Display vsock sockets (alias for -f vsock). --xdp Display XDP sockets (alias for -f xdp)." }, { "flag": "", "long": "--inet-sockopt", "arg": null, "description": "Display inet socket options." }, { "flag": "-f", "long": "--family", "arg": "FAMILY", "description": "Display sockets of type FAMILY. Currently the following families are supported: unix, inet, inet6, link, netlink, vsock, xdp." }, { "flag": "-A", "long": "--socket", "arg": "QUERY", "description": "List of socket tables to dump, separated by commas. The following identifiers are un‐ derstood: all, inet, tcp, udp, raw, unix, packet, netlink, unixdgram, unixstream, unixseqpacket, packetraw, packetdgram, dccp, sctp, vsockstream, vsockdgram, xdp Any item in the list may optionally be prefixed by an exclamation mark (!) to exclude that socket table from being dumped." }, { "flag": "-D", "long": "--diag", "arg": "FILE", "description": "Do not display anything, just dump raw information about TCP sockets to FILE after ap‐ plying filters. If FILE is - stdout is used." }, { "flag": "-F", "long": "--filter", "arg": "FILE", "description": "Read filter information from FILE. Each line of FILE is interpreted like single com‐ mand line option. If FILE is - stdin is used." } ], "examples": [], "see_also": [ { "name": "ip", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ip/8/json" } ] }