plucky (8) bpftool-link.8.gz

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)