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1.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)2 3================4bpftool-link5================6-------------------------------------------------------------------------------7tool for inspection and simple manipulation of eBPF links8-------------------------------------------------------------------------------9 10:Manual section: 811 12.. include:: substitutions.rst13 14SYNOPSIS15========16 17**bpftool** [*OPTIONS*] **link** *COMMAND*18 19*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }20 21*COMMANDS* := { **show** | **list** | **pin** | **help** }22 23LINK COMMANDS24=============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 34DESCRIPTION35===========36bpftool link { show | list } [*LINK*]37 Show information about active links. If *LINK* is specified show38 information only about given link, otherwise list all links currently39 active on the system.40 41 Output will start with link ID followed by link type and zero or more named42 attributes, some of which depend on type of link.43 44 Since Linux 5.8 bpftool is able to discover information about processes45 that hold open file descriptors (FDs) against BPF links. On such kernels46 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 dot52 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 stay56 valid, but they will be detached from the respective BPF hook and BPF link57 will transition into a defunct state until last open file descriptor for58 that link is closed.59 60bpftool link help61 Print short help message.62 63OPTIONS64=======65 .. include:: common_options.rst66 67 -f, --bpffs68 When showing BPF links, show file names of pinned links.69 70 -n, --nomount71 Do not automatically attempt to mount any virtual file system (such as72 tracefs or BPF virtual file system) when necessary.73 74EXAMPLES75========76**# bpftool link show**77 78::79 80 10: cgroup prog 2581 cgroup_id 614 attach_type egress82 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 link108