1BPFTOOL-LINK(8)                                                BPFTOOL-LINK(8)
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3
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NAME

6       bpftool-link  -  tool  for  inspection  and simple manipulation of eBPF
7       links
8

SYNOPSIS

10          bpftool [OPTIONS] link COMMAND
11
12          OPTIONS := { { -j | --json } [{ -p | --pretty }] | { -d | --debug  }
13          | { -f | --bpffs } | { -n | --nomount } }
14
15          COMMANDS := { show | list | pin | help }
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18       bpftool link { show | list } [LINK]
19       bpftool link pin LINK FILE
20       bpftool link detach LINK
21       bpftool link help
22
23       LINK := { id LINK_ID | pinned FILE }
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25

DESCRIPTION

27          bpftool link { show | list } [LINK]
28                 Show  information  about  active  links. If LINK is specified
29                 show information only about given link,  otherwise  list  all
30                 links currently active on the system.
31
32                 Output will start with link ID followed by link type and zero
33                 or more named attributes, some of which  depend  on  type  of
34                 link.
35
36                 Since Linux 5.8 bpftool is able to discover information about
37                 processes that hold open file descriptors (FDs)  against  BPF
38                 links.  On  such kernels bpftool will automatically emit this
39                 information as well.
40
41          bpftool link pin LINK FILE
42                 Pin link LINK as FILE.
43
44                 Note: FILE must be located in bpffs mount. It must  not  con‐
45                 tain  a dot character ('.'), which is reserved for future ex‐
46                 tensions of bpffs.
47
48          bpftool link detach LINK
49                 Force-detach link LINK. BPF link and its underlying BPF  pro‐
50                 gram  will stay valid, but they will be detached from the re‐
51                 spective BPF hook and BPF link will transition into a defunct
52                 state  until  last  open  file  descriptor  for  that link is
53                 closed.
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55          bpftool link help
56                 Print short help message.
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OPTIONS

59          -h, --help
60                 Print short help message (similar to bpftool help).
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62          -V, --version
63                 Print bpftool's version number (similar to bpftool  version),
64                 the  number  of  the libbpf version in use, and optional fea‐
65                 tures that were included when bpftool was compiled.  Optional
66                 features  include  linking  against LLVM or libbfd to provide
67                 the disassembler for  JIT-ted  programs  (bpftool  prog  dump
68                 jited) and usage of BPF skeletons (some features like bpftool
69                 prog profile or showing pids associated to  BPF  objects  may
70                 rely on it).
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72          -j, --json
73                 Generate  JSON output. For commands that cannot produce JSON,
74                 this option has no effect.
75
76          -p, --pretty
77                 Generate human-readable JSON output. Implies -j.
78
79          -d, --debug
80                 Print all logs available, even debug-level information.  This
81                 includes  logs from libbpf as well as from the verifier, when
82                 attempting to load programs.
83
84          -f, --bpffs
85                 When showing BPF links, show file names of pinned links.
86
87          -n, --nomount
88                 Do not automatically attempt to mount any virtual file system
89                 (such as tracefs or BPF virtual file system) when necessary.
90

EXAMPLES

92       # bpftool link show
93
94          10: cgroup  prog 25
95                  cgroup_id 614  attach_type egress
96                  pids test_progs(223)
97
98       # bpftool --json --pretty link show
99
100          [{
101                  "type": "cgroup",
102                  "prog_id": 25,
103                  "cgroup_id": 614,
104                  "attach_type": "egress",
105                  "pids": [{
106                          "pid": 223,
107                          "comm": "test_progs"
108                      }
109                  ]
110              }
111          ]
112
113       # bpftool link pin id 10 /sys/fs/bpf/link
114       # ls -l /sys/fs/bpf/
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116
117          -rw------- 1 root root 0 Apr 23 21:39 link
118

SEE ALSO

120          bpf(2),       bpf-helpers(7),       bpftool(8),      bpftool-btf(8),
121          bpftool-cgroup(8),        bpftool-feature(8),        bpftool-gen(8),
122          bpftool-iter(8),  bpftool-map(8),  bpftool-net(8),  bpftool-perf(8),
123          bpftool-prog(8), bpftool-struct_ops(8)
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128                                                               BPFTOOL-LINK(8)
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