7 lttng-snapshot - Take LTTng snapshots and configure snapshot outputs
12 Add a snapshot output:
15 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot add-output* [option:--max-size='SIZE']
16 [option:--name='NAME'] [option:--session='SESSION']
17 (option:--ctrl-url='URL' option:--data-url='URL' | 'URL')
19 Remove a snapshot output:
22 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot del-output* [option:--session='SESSION']
25 List current snapshot outputs:
28 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot list-output* [option:--session='SESSION']
33 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot record* [option:--max-size='SIZE']
34 [option:--name='NAME'] [option:--session='SESSION']
35 (option:--ctrl-url='URL' option:--data-url='URL' | 'URL')
40 The `lttng snapshot` command manages the snapshot outputs and takes
43 A _snapshot_ is a dump of the current sub-buffers of all the channels
44 of a given tracing session. When a snapshot is taken, the memory dump
45 is sent to the registered snapshot outputs.
47 The tracing session should be created in _snapshot mode_ to make sure
48 that taking snapshots is allowed. This is done at tracing session
49 creation time using the man:lttng-create(1) command's
50 nloption:--snapshot option.
52 Note that, when a snapshot is taken, the sub-buffers are not cleared.
53 This means that different recorded snapshots may contain the same
56 If you want, instead, to keep all the trace data, but divide it into
57 archived chunks which are then free to process (just like snapshots),
58 see the lttng-rotate(1) and lttng-enable-rotation(1) commands. Trace
59 chunk archives do not overlap like snapshots can.
64 Snapshot outputs are the destinations of snapshot files when a
65 snapshot is taken using the `record` action.
67 As of this version, only one snapshot output is allowed.
69 A snapshot output can be added using the `add-output` action. The
70 output destination URL is set using either the 'URL' positional
71 argument, or both the option:--ctrl-url and option:--data-url options.
72 See man:lttng-create(1) to learn more about the URL format.
74 A name can be assigned to an output when adding it using the
75 option:--name option. This name is part of the names of the
76 snapshot files written to this output.
78 By default, the snapshot files can be as big as the sum of the
79 sizes of all the sub-buffers or all the channels of the selected
80 tracing session. The maximum total size of all the snapshot files can
81 be configured using the option:--max-size option.
83 Snapshot outputs can be listed using the `list-output` action.
85 Snapshot outputs can be removed using the `del-output` action. The
86 configured name can be used when removing an output, or an ID as
87 listed by the `list-output` action.
92 Taking a snapshot of the current tracing session is as easy as:
96 $ lttng snapshot record
99 This writes the snapshot files to the configured output. It is possible
100 to use a custom, unregistered output at record time using the same
101 options supported by the `add-output` action.
103 NOTE: Before taking a snapshot on a system with a high event throughput,
104 it is recommended to first run `lttng stop` (see
105 man:lttng-stop(1)). Otherwise, the snapshot could contain "holes",
106 the result of the tracers overwriting unconsumed trace packets during
107 the record operation. After the snapshot is recorded, the tracers can be
108 started again with `lttng start` (see man:lttng-start(1)).
111 include::common-cmd-options-head.txt[]
116 option:-s 'SESSION', option:--session='SESSION'::
117 Take a snapshot of the sub-buffers of the channels contained in
118 the tracing session named 'SESSION' instead of the current
124 option:-C 'URL', option:--ctrl-url='URL'::
125 Set control path URL to 'URL' (must use option:--data-url option
128 option:-D 'URL', option:--data-url='URL'::
129 Set data path URL to 'URL' (must use option:--ctrl-url option
132 option:-m 'SIZE', option:--max-size='SIZE'::
133 Limit the total size of all the snapshot files written when
134 recording a snapshot to 'SIZE' bytes. The `k` (kiB), `M` (MiB),
135 and `G` (GiB) suffixes are supported.
137 option:-n 'NAME', option:--name='NAME'::
138 Assign the name 'NAME' to the snapshot output.
141 include::common-cmd-help-options.txt[]
144 include::common-cmd-footer.txt[]