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 version number (similar to bpftool version), and  optional  features  that
                 were  included  when  bpftool  was  compiled.  Optional features include linking
                 against 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)