Manual: bpftool-link

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-to‐
       ken(8)

													     bpftool-link(8)