NAME

       bpftool-link - tool for inspection and simple manipulation of eBPF links

SYNOPSIS

          bpftool [OPTIONS] link COMMAND

          OPTIONS := { { -j | --json } [{ -p | --pretty }] | { -d | --debug } | { -l | --legacy }
          | { -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  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.

          -l, --legacy
                 Use  legacy  libbpf  mode  which  has  more relaxed BPF program requirements. By
                 default, bpftool has more  strict  requirements  about  section  names,  changes
                 pinning logic and doesn't support some of the older non-BTF map declarations.

                 See https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0 for details.

          -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)