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.TH "BPFTOOL-LINK" 8 "" ""
.SH NAME
bpftool-link \- tool for inspection and simple manipulation of eBPF links
.SH SYNOPSIS
.INDENT 0.0
.INDENT 3.5
\fBbpftool\fP [\fIOPTIONS\fP] \fBlink\fP \fICOMMAND\fP
.sp
\fIOPTIONS\fP := { { \fB\-j\fP | \fB\-\-json\fP } [{ \fB\-p\fP | \fB\-\-pretty\fP }] | { \fB\-d\fP | \fB\-\-debug\fP } | { \fB\-f\fP | \fB\-\-bpffs\fP } | { \fB\-n\fP | \fB\-\-nomount\fP } }
.sp
\fICOMMANDS\fP := { \fBshow\fP | \fBlist\fP | \fBpin\fP | \fBhelp\fP }
.UNINDENT
.UNINDENT
.SH LINK COMMANDS
.nf
\fBbpftool\fP \fBlink { show | list }\fP [\fILINK\fP]
\fBbpftool\fP \fBlink pin\fP \fILINK\fP \fIFILE\fP
\fBbpftool\fP \fBlink detach\fP \fILINK\fP
\fBbpftool\fP \fBlink help\fP

\fILINK\fP := { \fBid\fP \fILINK_ID\fP | \fBpinned\fP \fIFILE\fP }
.fi
.sp
.SH DESCRIPTION
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.TP
.B \fBbpftool link { show | list }\fP [\fILINK\fP]
Show information about active links. If \fILINK\fP is
specified show information only about given link,
otherwise list all links currently active on the system.
.sp
Output will start with link ID followed by link type and
zero or more named attributes, some of which depend on type
of link.
.sp
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.
.TP
.B \fBbpftool link pin\fP \fILINK\fP \fIFILE\fP
Pin link \fILINK\fP as \fIFILE\fP\&.
.sp
Note: \fIFILE\fP must be located in \fIbpffs\fP mount. It must not
contain a dot character (\(aq.\(aq), which is reserved for future
extensions of \fIbpffs\fP\&.
.TP
.B \fBbpftool link detach\fP \fILINK\fP
Force\-detach link \fILINK\fP\&. 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.
.TP
.B \fBbpftool link help\fP
Print short help message.
.UNINDENT
.UNINDENT
.UNINDENT
.SH OPTIONS
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.TP
.B  \-h\fP,\fB  \-\-help
Print short help message (similar to \fBbpftool help\fP).
.TP
.B  \-V\fP,\fB  \-\-version
Print bpftool\(aqs version number (similar to \fBbpftool version\fP), the
number of the libbpf version in use, and optional features that were
included when bpftool was compiled. Optional features include linking
against LLVM or libbfd to provide the disassembler for JIT\-ted
programs (\fBbpftool prog dump jited\fP) and usage of BPF skeletons
(some features like \fBbpftool prog profile\fP or showing pids
associated to BPF objects may rely on it).
.TP
.B  \-j\fP,\fB  \-\-json
Generate JSON output. For commands that cannot produce JSON, this
option has no effect.
.TP
.B  \-p\fP,\fB  \-\-pretty
Generate human\-readable JSON output. Implies \fB\-j\fP\&.
.TP
.B  \-d\fP,\fB  \-\-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.
.UNINDENT
.INDENT 0.0
.TP
.B  \-f\fP,\fB  \-\-bpffs
When showing BPF links, show file names of pinned
links.
.TP
.B  \-n\fP,\fB  \-\-nomount
Do not automatically attempt to mount any virtual file system
(such as tracefs or BPF virtual file system) when necessary.
.UNINDENT
.UNINDENT
.UNINDENT
.SH EXAMPLES
.sp
\fB# bpftool link show\fP
.INDENT 0.0
.INDENT 3.5
.sp
.EX
10: cgroup  prog 25
        cgroup_id 614  attach_type egress
        pids test_progs(223)
.EE
.UNINDENT
.UNINDENT
.sp
\fB# bpftool \-\-json \-\-pretty link show\fP
.INDENT 0.0
.INDENT 3.5
.sp
.EX
[{
        \(dqtype\(dq: \(dqcgroup\(dq,
        \(dqprog_id\(dq: 25,
        \(dqcgroup_id\(dq: 614,
        \(dqattach_type\(dq: \(dqegress\(dq,
        \(dqpids\(dq: [{
                \(dqpid\(dq: 223,
                \(dqcomm\(dq: \(dqtest_progs\(dq
            }
        ]
    }
]
.EE
.UNINDENT
.UNINDENT
.nf

\fB# bpftool link pin id 10 /sys/fs/bpf/link\fP
\fB# ls \-l /sys/fs/bpf/\fP
.fi
.sp
.INDENT 0.0
.INDENT 3.5
.sp
.EX
\-rw\-\-\-\-\-\-\- 1 root root 0 Apr 23 21:39 link
.EE
.UNINDENT
.UNINDENT
.SH SEE ALSO
.INDENT 0.0
.INDENT 3.5
\fBbpf\fP(2),
\fBbpf\-helpers\fP(7),
\fBbpftool\fP(8),
\fBbpftool\-btf\fP(8),
\fBbpftool\-cgroup\fP(8),
\fBbpftool\-feature\fP(8),
\fBbpftool\-gen\fP(8),
\fBbpftool\-iter\fP(8),
\fBbpftool\-map\fP(8),
\fBbpftool\-net\fP(8),
\fBbpftool\-perf\fP(8),
\fBbpftool\-prog\fP(8),
\fBbpftool\-struct_ops\fP(8)
.UNINDENT
.UNINDENT
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