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