.. 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
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