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===========
 36	**bpftool link { show | list }** [*LINK*]
 37		  Show information about active links. If *LINK* is
 38		  specified show information only about given link,
 39		  otherwise list all links currently active on the system.
 40
 41		  Output will start with link ID followed by link type and
 42		  zero or more named attributes, some of which depend on type
 43		  of link.
 44
 45		  Since Linux 5.8 bpftool is able to discover information about
 46		  processes that hold open file descriptors (FDs) against BPF
 47		  links. On such kernels bpftool will automatically emit this
 48		  information as well.
 49
 50	**bpftool link pin** *LINK* *FILE*
 51		  Pin link *LINK* as *FILE*.
 52
 53		  Note: *FILE* must be located in *bpffs* mount. It must not
 54		  contain a dot character ('.'), which is reserved for future
 55		  extensions of *bpffs*.
 56
 57	**bpftool link detach** *LINK*
 58		  Force-detach link *LINK*. BPF link and its underlying BPF
 59		  program will stay valid, but they will be detached from the
 60		  respective BPF hook and BPF link will transition into
 61		  a defunct state until last open file descriptor for that
 62		  link is closed.
 63
 64	**bpftool link help**
 65		  Print short help message.
 66
 67OPTIONS
 68=======
 69	.. include:: common_options.rst
 70
 71	-f, --bpffs
 72		  When showing BPF links, show file names of pinned
 73		  links.
 74
 75	-n, --nomount
 76		  Do not automatically attempt to mount any virtual file system
 77		  (such as tracefs or BPF virtual file system) when necessary.
 78
 79EXAMPLES
 80========
 81**# bpftool link show**
 82
 83::
 84
 85    10: cgroup  prog 25
 86            cgroup_id 614  attach_type egress
 87            pids test_progs(223)
 88
 89**# bpftool --json --pretty link show**
 90
 91::
 92
 93    [{
 94            "type": "cgroup",
 95            "prog_id": 25,
 96            "cgroup_id": 614,
 97            "attach_type": "egress",
 98            "pids": [{
 99                    "pid": 223,
100                    "comm": "test_progs"
101                }
102            ]
103        }
104    ]
105
106|
107| **# bpftool link pin id 10 /sys/fs/bpf/link**
108| **# ls -l /sys/fs/bpf/**
109
110::
111
112    -rw------- 1 root root 0 Apr 23 21:39 link