1.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
  2
  3================
  4bpftool-link
  5================
  6-------------------------------------------------------------------------------
  7tool for inspection and simple manipulation of eBPF links
  8-------------------------------------------------------------------------------
  9
 10:Manual section: 8
 11
 12.. include:: substitutions.rst
 13
 14SYNOPSIS
 15========
 16
 17**bpftool** [*OPTIONS*] **link** *COMMAND*
 18
 19*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }
 20
 21*COMMANDS* := { **show** | **list** | **pin** | **help** }
 22
 23LINK COMMANDS
 24=============
 25
 26| **bpftool** **link { show | list }** [*LINK*]
 27| **bpftool** **link pin** *LINK* *FILE*
 28| **bpftool** **link detach** *LINK*
 29| **bpftool** **link help**
 30|
 31| *LINK* := { **id** *LINK_ID* | **pinned** *FILE* }
 32
 33
 34DESCRIPTION
 35===========
 36bpftool link { show | list } [*LINK*]
 37    Show information about active links. If *LINK* is specified show
 38    information only about given link, otherwise list all links currently
 39    active on the system.
 40
 41    Output will start with link ID followed by link type and zero or more named
 42    attributes, some of which depend on type of link.
 43
 44    Since Linux 5.8 bpftool is able to discover information about processes
 45    that hold open file descriptors (FDs) against BPF links. On such kernels
 46    bpftool will automatically emit this information as well.
 47
 48bpftool link pin *LINK* *FILE*
 49    Pin link *LINK* as *FILE*.
 50
 51    Note: *FILE* must be located in *bpffs* mount. It must not contain a dot
 52    character ('.'), which is reserved for future extensions of *bpffs*.
 53
 54bpftool link detach *LINK*
 55    Force-detach link *LINK*. BPF link and its underlying BPF program will stay
 56    valid, but they will be detached from the respective BPF hook and BPF link
 57    will transition into a defunct state until last open file descriptor for
 58    that link is closed.
 59
 60bpftool link help
 61    Print short help message.
 62
 63OPTIONS
 64=======
 65    .. include:: common_options.rst
 66
 67    -f, --bpffs
 68        When showing BPF links, show file names of pinned links.
 69
 70    -n, --nomount
 71        Do not automatically attempt to mount any virtual file system (such as
 72        tracefs or BPF virtual file system) when necessary.
 73
 74EXAMPLES
 75========
 76**# bpftool link show**
 77
 78::
 79
 80    10: cgroup  prog 25
 81            cgroup_id 614  attach_type egress
 82            pids test_progs(223)
 83
 84**# bpftool --json --pretty link show**
 85
 86::
 87
 88    [{
 89            "type": "cgroup",
 90            "prog_id": 25,
 91            "cgroup_id": 614,
 92            "attach_type": "egress",
 93            "pids": [{
 94                    "pid": 223,
 95                    "comm": "test_progs"
 96                }
 97            ]
 98        }
 99    ]
100
101|
102| **# bpftool link pin id 10 /sys/fs/bpf/link**
103| **# ls -l /sys/fs/bpf/**
104
105::
106
107    -rw------- 1 root root 0 Apr 23 21:39 link