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=========== 36 **bpftool link { show | list }** [*LINK*] 37 Show information about active links. If *LINK* is 38 specified show information only about given link, 39 otherwise list all links currently active on the system. 40 41 Output will start with link ID followed by link type and 42 zero or more named attributes, some of which depend on type 43 of link. 44 45 Since Linux 5.8 bpftool is able to discover information about 46 processes that hold open file descriptors (FDs) against BPF 47 links. On such kernels bpftool will automatically emit this 48 information as well. 49 50 **bpftool link pin** *LINK* *FILE* 51 Pin link *LINK* as *FILE*. 52 53 Note: *FILE* must be located in *bpffs* mount. It must not 54 contain a dot character ('.'), which is reserved for future 55 extensions of *bpffs*. 56 57 **bpftool link detach** *LINK* 58 Force-detach link *LINK*. BPF link and its underlying BPF 59 program will stay valid, but they will be detached from the 60 respective BPF hook and BPF link will transition into 61 a defunct state until last open file descriptor for that 62 link is closed. 63 64 **bpftool link help** 65 Print short help message. 66 67OPTIONS 68======= 69 .. include:: common_options.rst 70 71 -f, --bpffs 72 When showing BPF links, show file names of pinned 73 links. 74 75 -n, --nomount 76 Do not automatically attempt to mount any virtual file system 77 (such as tracefs or BPF virtual file system) when necessary. 78 79EXAMPLES 80======== 81**# bpftool link show** 82 83:: 84 85 10: cgroup prog 25 86 cgroup_id 614 attach_type egress 87 pids test_progs(223) 88 89**# bpftool --json --pretty link show** 90 91:: 92 93 [{ 94 "type": "cgroup", 95 "prog_id": 25, 96 "cgroup_id": 614, 97 "attach_type": "egress", 98 "pids": [{ 99 "pid": 223, 100 "comm": "test_progs" 101 } 102 ] 103 } 104 ] 105 106| 107| **# bpftool link pin id 10 /sys/fs/bpf/link** 108| **# ls -l /sys/fs/bpf/** 109 110:: 111 112 -rw------- 1 root root 0 Apr 23 21:39 link 113