BPFTOOL-LINK(8) System Manager's Manual BPFTOOL-LINK(8)
NAME
bpftool-link - tool for inspection and simple manipulation of eBPF
links
SYNOPSIS
bpftool [OPTIONS] link COMMAND
OPTIONS := { { -j | --json } [{ -p | --pretty }] | { -d | --debug }
| { -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 con-
tain a dot character ('.'), which is reserved for future ex-
tensions of bpffs.
bpftool link detach LINK
Force-detach link LINK. BPF link and its underlying BPF pro-
gram will stay valid, but they will be detached from the re-
spective 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
-h, --help
Print short help message (similar to bpftool help).
-V, --version
Print bpftool's version number (similar to bpftool version),
the number of the libbpf version in use, and optional fea-
tures that were included when bpftool was compiled. Optional
features include linking against LLVM or libbfd to provide
the disassembler for JIT-ted programs (bpftool prog dump
jited) and usage of BPF skeletons (some features like bpftool
prog profile or showing pids associated to BPF objects may
rely on it).
-j, --json
Generate JSON output. For commands that cannot produce JSON,
this option has no effect.
-p, --pretty
Generate human-readable JSON output. Implies -j.
-d, --debug
Print all logs available, even debug-level information. This
includes logs from libbpf as well as from the verifier, when
attempting to load programs.
-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
SEE ALSO
bpf(2), bpf-helpers(7), bpftool(8), bpftool-btf(8),
bpftool-cgroup(8), bpftool-feature(8), bpftool-gen(8),
bpftool-iter(8), bpftool-map(8), bpftool-net(8), bpftool-perf(8),
bpftool-prog(8), bpftool-struct_ops(8)
BPFTOOL-LINK(8)
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