1.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) 2 3================ 4bpftool-link 5================ 6------------------------------------------------------------------------------- 7tool for inspection and simple manipulation of eBPF links 8------------------------------------------------------------------------------- 9 10:Manual section: 8 11 12SYNOPSIS 13======== 14 15 **bpftool** [*OPTIONS*] **link** *COMMAND* 16 17 *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | { **-d** | **--debug** } | 18 { **-f** | **--bpffs** } | { **-n** | **--nomount** } } 19 20 *COMMANDS* := { **show** | **list** | **pin** | **help** } 21 22LINK COMMANDS 23============= 24 25| **bpftool** **link { show | list }** [*LINK*] 26| **bpftool** **link pin** *LINK* *FILE* 27| **bpftool** **link detach** *LINK* 28| **bpftool** **link help** 29| 30| *LINK* := { **id** *LINK_ID* | **pinned** *FILE* } 31 32 33DESCRIPTION 34=========== 35 **bpftool link { show | list }** [*LINK*] 36 Show information about active links. If *LINK* is 37 specified show information only about given link, 38 otherwise list all links currently active on the system. 39 40 Output will start with link ID followed by link type and 41 zero or more named attributes, some of which depend on type 42 of link. 43 44 Since Linux 5.8 bpftool is able to discover information about 45 processes that hold open file descriptors (FDs) against BPF 46 links. On such kernels bpftool will automatically emit this 47 information as well. 48 49 **bpftool link pin** *LINK* *FILE* 50 Pin link *LINK* as *FILE*. 51 52 Note: *FILE* must be located in *bpffs* mount. It must not 53 contain a dot character ('.'), which is reserved for future 54 extensions of *bpffs*. 55 56 **bpftool link detach** *LINK* 57 Force-detach link *LINK*. BPF link and its underlying BPF 58 program will stay valid, but they will be detached from the 59 respective BPF hook and BPF link will transition into 60 a defunct state until last open file descriptor for that 61 link is closed. 62 63 **bpftool link help** 64 Print short help message. 65 66OPTIONS 67======= 68 .. include:: common_options.rst 69 70 -f, --bpffs 71 When showing BPF links, show file names of pinned 72 links. 73 74 -n, --nomount 75 Do not automatically attempt to mount any virtual file system 76 (such as tracefs or BPF virtual file system) when necessary. 77 78EXAMPLES 79======== 80**# bpftool link show** 81 82:: 83 84 10: cgroup prog 25 85 cgroup_id 614 attach_type egress 86 pids test_progs(223) 87 88**# bpftool --json --pretty link show** 89 90:: 91 92 [{ 93 "type": "cgroup", 94 "prog_id": 25, 95 "cgroup_id": 614, 96 "attach_type": "egress", 97 "pids": [{ 98 "pid": 223, 99 "comm": "test_progs" 100 } 101 ] 102 } 103 ] 104 105| 106| **# bpftool link pin id 10 /sys/fs/bpf/link** 107| **# ls -l /sys/fs/bpf/** 108 109:: 110 111 -rw------- 1 root root 0 Apr 23 21:39 link 112