1 .. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2
3 ================
4 bpftool-link
5 ================
6 -------------------------------------------------------------------------------
7 tool for inspection and simple manipulation of eBPF links
8 -------------------------------------------------------------------------------
9
10 :Manual section: 8
11
12 .. include:: substitutions.rst
13
14 SYNOPSIS
15 ========
16
17 **bpftool** [*OPTIONS*] **link** *COMMAND*
18
19 *OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }
20
21 *COMMANDS* := { **show** | **list** | **pin** | **help** }
22
23 LINK 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
34 DESCRIPTION
35 ===========
36 bpftool 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
48 bpftool 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
54 bpftool 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
60 bpftool link help
61 Print short help message.
62
63 OPTIONS
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
74 EXAMPLES
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
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