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
                 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

          -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
                 features 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)