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.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
================
bpftool-link
================
-------------------------------------------------------------------------------
tool for inspection and simple manipulation of eBPF links
-------------------------------------------------------------------------------
:Manual section: 8
.. include:: substitutions.rst
SYNOPSIS
========
**bpftool** [*OPTIONS*] **link** *COMMAND*
*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }
*COMMANDS* := { **show** | **list** | **pin** | **help** }
LINK COMMANDS
=============
| **bpftool** **link { show | list }** [*LINK*]
| **bpftool** **link pin** *LINK* *FILE*
| **bpftool** **link detach** *LINK*
| **bpftool** **link help**
|
| *LINK* := { **id** *LINK_ID* | **pinned** *FILE* }
DESCRIPTION
===========
**bpftool link { show | list }** [*LINK*]
Show information about active links. If *LINK* is
specified show information only about given link,
otherwise list all links currently active on the system.
Output will start with link ID followed by link type and
zero or more named attributes, some of which depend on type
of link.
Since Linux 5.8 bpftool is able to discover information about
processes that hold open file descriptors (FDs) against BPF
links. On such kernels bpftool will automatically emit this
information as well.
**bpftool link pin** *LINK* *FILE*
Pin link *LINK* as *FILE*.
Note: *FILE* must be located in *bpffs* mount. It must not
contain a dot character ('.'), which is reserved for future
extensions of *bpffs*.
**bpftool link detach** *LINK*
Force-detach link *LINK*. BPF link and its underlying BPF
program will stay valid, but they will be detached from the
respective BPF hook and BPF link will transition into
a defunct state until last open file descriptor for that
link is closed.
**bpftool link help**
Print short help message.
OPTIONS
=======
.. include:: common_options.rst
-f, --bpffs
When showing BPF links, show file names of pinned
links.
-n, --nomount
Do not automatically attempt to mount any virtual file system
(such as tracefs or BPF virtual file system) when necessary.
EXAMPLES
========
**# bpftool link show**
::
10: cgroup prog 25
cgroup_id 614 attach_type egress
pids test_progs(223)
**# bpftool --json --pretty link show**
::
[{
"type": "cgroup",
"prog_id": 25,
"cgroup_id": 614,
"attach_type": "egress",
"pids": [{
"pid": 223,
"comm": "test_progs"
}
]
}
]
|
| **# bpftool link pin id 10 /sys/fs/bpf/link**
| **# ls -l /sys/fs/bpf/**
::
-rw------- 1 root root 0 Apr 23 21:39 link
|
