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)