================
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bpftool-link
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================
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-------------------------------------------------------------------------------
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tool for inspection and simple manipulation of eBPF links
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-------------------------------------------------------------------------------
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:Manual section: 8
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SYNOPSIS
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========
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**bpftool** [*OPTIONS*] **link** *COMMAND*
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*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | { **-f** | **--bpffs** } }
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*COMMANDS* := { **show** | **list** | **pin** | **help** }
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LINK COMMANDS
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=============
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| **bpftool** **link { show | list }** [*LINK*]
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| **bpftool** **link pin** *LINK* *FILE*
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| **bpftool** **link detach** *LINK*
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| **bpftool** **link help**
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| *LINK* := { **id** *LINK_ID* | **pinned** *FILE* }
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DESCRIPTION
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===========
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**bpftool link { show | list }** [*LINK*]
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Show information about active links. If *LINK* is
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specified show information only about given link,
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otherwise list all links currently active on the system.
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Output will start with link ID followed by link type and
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zero or more named attributes, some of which depend on type
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of link.
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Since Linux 5.8 bpftool is able to discover information about
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processes that hold open file descriptors (FDs) against BPF
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links. On such kernels bpftool will automatically emit this
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information as well.
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**bpftool link pin** *LINK* *FILE*
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Pin link *LINK* as *FILE*.
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Note: *FILE* must be located in *bpffs* mount. It must not
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contain a dot character ('.'), which is reserved for future
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extensions of *bpffs*.
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**bpftool link detach** *LINK*
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Force-detach link *LINK*. BPF link and its underlying BPF
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program will stay valid, but they will be detached from the
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respective BPF hook and BPF link will transition into
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a defunct state until last open file descriptor for that
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link is closed.
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**bpftool link help**
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Print short help message.
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OPTIONS
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=======
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.. include:: common_options.rst
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-f, --bpffs
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When showing BPF links, show file names of pinned
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links.
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-n, --nomount
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Do not automatically attempt to mount any virtual file system
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(such as tracefs or BPF virtual file system) when necessary.
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EXAMPLES
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========
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**# bpftool link show**
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::
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10: cgroup prog 25
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cgroup_id 614 attach_type egress
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pids test_progs(223)
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**# bpftool --json --pretty link show**
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::
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[{
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"type": "cgroup",
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"prog_id": 25,
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"cgroup_id": 614,
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"attach_type": "egress",
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"pids": [{
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"pid": 223,
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"comm": "test_progs"
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}
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]
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}
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]
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| **# bpftool link pin id 10 /sys/fs/bpf/link**
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| **# ls -l /sys/fs/bpf/**
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::
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-rw------- 1 root root 0 Apr 23 21:39 link
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