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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
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