1================
2bpftool-link
3================
4-------------------------------------------------------------------------------
5tool for inspection and simple manipulation of eBPF links
6-------------------------------------------------------------------------------
7
8:Manual section: 8
9
10SYNOPSIS
11========
12
13	**bpftool** [*OPTIONS*] **link** *COMMAND*
14
15	*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | { **-f** | **--bpffs** } }
16
17	*COMMANDS* := { **show** | **list** | **pin** | **help** }
18
19LINK COMMANDS
20=============
21
22|	**bpftool** **link { show | list }** [*LINK*]
23|	**bpftool** **link pin** *LINK* *FILE*
24|	**bpftool** **link detach** *LINK*
25|	**bpftool** **link help**
26|
27|	*LINK* := { **id** *LINK_ID* | **pinned** *FILE* }
28
29
30DESCRIPTION
31===========
32	**bpftool link { show | list }** [*LINK*]
33		  Show information about active links. If *LINK* is
34		  specified show information only about given link,
35		  otherwise list all links currently active on the system.
36
37		  Output will start with link ID followed by link type and
38		  zero or more named attributes, some of which depend on type
39		  of link.
40
41		  Since Linux 5.8 bpftool is able to discover information about
42		  processes that hold open file descriptors (FDs) against BPF
43		  links. On such kernels bpftool will automatically emit this
44		  information as well.
45
46	**bpftool link pin** *LINK* *FILE*
47		  Pin link *LINK* as *FILE*.
48
49		  Note: *FILE* must be located in *bpffs* mount. It must not
50		  contain a dot character ('.'), which is reserved for future
51		  extensions of *bpffs*.
52
53	**bpftool link detach** *LINK*
54		  Force-detach link *LINK*. BPF link and its underlying BPF
55		  program will stay valid, but they will be detached from the
56		  respective BPF hook and BPF link will transition into
57		  a defunct state until last open file descriptor for that
58		  link is closed.
59
60	**bpftool 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
69		  links.
70
71	-n, --nomount
72		  Do not automatically attempt to mount any virtual file system
73		  (such as tracefs or BPF virtual file system) when necessary.
74
75EXAMPLES
76========
77**# bpftool link show**
78
79::
80
81    10: cgroup  prog 25
82            cgroup_id 614  attach_type egress
83            pids test_progs(223)
84
85**# bpftool --json --pretty link show**
86
87::
88
89    [{
90            "type": "cgroup",
91            "prog_id": 25,
92            "cgroup_id": 614,
93            "attach_type": "egress",
94            "pids": [{
95                    "pid": 223,
96                    "comm": "test_progs"
97                }
98            ]
99        }
100    ]
101
102|
103| **# bpftool link pin id 10 /sys/fs/bpf/link**
104| **# ls -l /sys/fs/bpf/**
105
106::
107
108    -rw------- 1 root root 0 Apr 23 21:39 link
109