1================
  2bpftool-link
  3================
  4-------------------------------------------------------------------------------
  5tool for inspection and simple manipulation of eBPF links
  6-------------------------------------------------------------------------------
  7
  8:Manual section: 8
  9
 10SYNOPSIS
 11========
 12
 13	**bpftool** [*OPTIONS*] **link** *COMMAND*
 14
 15	*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | { **-f** | **--bpffs** } }
 16
 17	*COMMANDS* := { **show** | **list** | **pin** | **help** }
 18
 19LINK COMMANDS
 20=============
 21
 22|	**bpftool** **link { show | list }** [*LINK*]
 23|	**bpftool** **link pin** *LINK* *FILE*
 24|	**bpftool** **link detach** *LINK*
 25|	**bpftool** **link help**
 26|
 27|	*LINK* := { **id** *LINK_ID* | **pinned** *FILE* }
 28
 29
 30DESCRIPTION
 31===========
 32	**bpftool link { show | list }** [*LINK*]
 33		  Show information about active links. If *LINK* is
 34		  specified show information only about given link,
 35		  otherwise list all links currently active on the system.
 36
 37		  Output will start with link ID followed by link type and
 38		  zero or more named attributes, some of which depend on type
 39		  of link.
 40
 41		  Since Linux 5.8 bpftool is able to discover information about
 42		  processes that hold open file descriptors (FDs) against BPF
 43		  links. On such kernels bpftool will automatically emit this
 44		  information as well.
 45
 46	**bpftool link pin** *LINK* *FILE*
 47		  Pin link *LINK* as *FILE*.
 48
 49		  Note: *FILE* must be located in *bpffs* mount. It must not
 50		  contain a dot character ('.'), which is reserved for future
 51		  extensions of *bpffs*.
 52
 53	**bpftool link detach** *LINK*
 54		  Force-detach link *LINK*. BPF link and its underlying BPF
 55		  program will stay valid, but they will be detached from the
 56		  respective BPF hook and BPF link will transition into
 57		  a defunct state until last open file descriptor for that
 58		  link is closed.
 59
 60	**bpftool link help**
 61		  Print short help message.
 62
 63OPTIONS
 64=======
 65	.. include:: common_options.rst
 66
 67	-f, --bpffs
 68		  When showing BPF links, show file names of pinned
 69		  links.
 70
 71	-n, --nomount
 72		  Do not automatically attempt to mount any virtual file system
 73		  (such as tracefs or BPF virtual file system) when necessary.
 74
 75EXAMPLES
 76========
 77**# bpftool link show**
 78
 79::
 80
 81    10: cgroup  prog 25
 82            cgroup_id 614  attach_type egress
 83            pids test_progs(223)
 84
 85**# bpftool --json --pretty link show**
 86
 87::
 88
 89    [{
 90            "type": "cgroup",
 91            "prog_id": 25,
 92            "cgroup_id": 614,
 93            "attach_type": "egress",
 94            "pids": [{
 95                    "pid": 223,
 96                    "comm": "test_progs"
 97                }
 98            ]
 99        }
100    ]
101
102|
103| **# bpftool link pin id 10 /sys/fs/bpf/link**
104| **# ls -l /sys/fs/bpf/**
105
106::
107
108    -rw------- 1 root root 0 Apr 23 21:39 link