projects / lttng-tools.git / blame
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|---|---|---|
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1 | lttng-snapshot(1) |
| 2 | ================= | |
| 3 | ||
| 4 | ||
| 5 | NAME | |
| 6 | ---- | |
| 7 | lttng-snapshot - Take LTTng snapshots and configure snapshot outputs | |
| 8 | ||
| 9 | ||
| 10 | SYNOPSIS | |
| 11 | -------- | |
| 12 | Add a snapshot output: | |
| 13 | ||
| 14 | [verse] | |
| ce19b9ed | 15 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot add-output* [option:--max-size='SIZE'] |
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16 | [option:--name='NAME'] [option:--session='SESSION'] |
| 17 | (option:--ctrl-url='URL' option:--data-url='URL' | 'URL') | |
| 18 | ||
| 19 | Remove a snapshot output: | |
| 20 | ||
| 21 | [verse] | |
| ce19b9ed | 22 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot del-output* [option:--session='SESSION'] |
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23 | ('ID' | 'NAME') |
| 24 | ||
| 25 | List current snapshot outputs: | |
| 26 | ||
| 27 | [verse] | |
| ce19b9ed | 28 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot list-output* [option:--session='SESSION'] |
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29 | |
| 30 | Take a snapshot: | |
| 31 | ||
| 32 | [verse] | |
| ce19b9ed | 33 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot record* [option:--max-size='SIZE'] |
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34 | [option:--name='NAME'] [option:--session='SESSION'] |
| 35 | (option:--ctrl-url='URL' option:--data-url='URL' | 'URL') | |
| 36 | ||
| 37 | ||
| 38 | DESCRIPTION | |
| 39 | ----------- | |
| 40 | The `lttng snapshot` command manages the snapshot outputs and takes | |
| 41 | snapshots. | |
| 42 | ||
| 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. | |
| 46 | ||
| 47 | The tracing session should be created in _snapshot mode_ to make sure | |
| 48 | taking snapshots is allowed. This is done at tracing session creation | |
| 7c1a4458 | 49 | time using the man:lttng-create(1) command. |
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50 | |
| 51 | Note that, when a snapshot is taken, the sub-buffers are not cleared. | |
| 52 | This means that different recorded snapshots may contain the same | |
| 53 | events. | |
| 54 | ||
| 55 | ||
| 56 | Snapshot outputs | |
| 57 | ~~~~~~~~~~~~~~~~ | |
| 58 | Snapshot outputs are the destinations of snapshot files when a | |
| 59 | snapshot is taken using the `record` action. | |
| 60 | ||
| 61 | As of this version, only one snapshot output is allowed. | |
| 62 | ||
| 63 | A snapshot output can be added using the `add-output` action. The | |
| 64 | output destination URL is set using either the 'URL' positional | |
| 65 | argument, or both the option:--ctrl-url and option:--data-url options. | |
| 7c1a4458 | 66 | See man:lttng-create(1) to learn more about the URL format. |
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67 | |
| 68 | A name can be assigned to an output when adding it using the | |
| 69 | option:--name option. This name is part of the names of the | |
| 70 | snapshot files written to this output. | |
| 71 | ||
| 72 | By default, the snapshot files can be as big as the sum of the | |
| 73 | sizes of all the sub-buffers or all the channels of the selected | |
| 74 | tracing session. The maximum total size of all the snapshot files can | |
| 75 | be configured using the option:--max-size option. | |
| 76 | ||
| 77 | Snapshot outputs can be listed using the `list-output` action. | |
| 78 | ||
| 79 | Snapshot outputs can be removed using the `del-output` action. The | |
| 80 | configured name can be used when removing an output, or an ID as | |
| 81 | listed by the `list-output` action. | |
| 82 | ||
| 83 | ||
| 84 | Taking a snapshot | |
| 85 | ~~~~~~~~~~~~~~~~~ | |
| 86 | Taking a snapshot of the current tracing session is as easy as: | |
| 87 | ||
| 88 | --------------------- | |
| 89 | lttng snapshot record | |
| 90 | --------------------- | |
| 91 | ||
| 92 | This writes the snapshot files to the configured output. It is possible | |
| 93 | to use a custom, unregistered output at record time using the same | |
| 94 | options supported by the `add-output` action. | |
| 95 | ||
| 96 | NOTE: Before taking a snapshot on a system with a high event throughput, | |
| 97 | it is recommended to first run `lttng stop` (see | |
| 7c1a4458 | 98 | man:lttng-stop(1)). Otherwise, the snapshot could contain "holes", |
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99 | the result of the tracers overwriting unconsumed trace packets during |
| 100 | the record operation. After the snapshot is recorded, the tracers can be | |
| 7c1a4458 | 101 | started again with `lttng start` (see man:lttng-start(1)). |
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102 | |
| 103 | ||
| 104 | include::common-cmd-options-head.txt[] | |
| 105 | ||
| 106 | ||
| 107 | Target | |
| 108 | ~~~~~~ | |
| 109 | option:-s, option:--session='SESSION':: | |
| 110 | Take a snapshot of the sub-buffers of the channels contained in | |
| 111 | the tracing session named 'SESSION' instead of the current | |
| 112 | tracing session. | |
| 113 | ||
| 114 | ||
| 115 | Snapshot output | |
| 116 | ~~~~~~~~~~~~~~~ | |
| 117 | option:-C, option:--ctrl-url='URL':: | |
| 118 | Set control path URL to 'URL' (must use option:--data-url option | |
| 119 | also). | |
| 120 | ||
| 121 | option:-D, option:--data-url='URL':: | |
| 122 | Set data path URL to 'URL' (must use option:--ctrl-url option | |
| 123 | also). | |
| 124 | ||
| 125 | option:-m, option:--max-size='SIZE':: | |
| 126 | Limit the total size of all the snapshot files written when | |
| 127 | recording a snapshot to 'SIZE' bytes. The `k` (kiB), `M` (MiB), | |
| 128 | and `G` (GiB) suffixes are supported. | |
| 129 | ||
| 130 | option:-n, option:--name='NAME':: | |
| 131 | Assign the name 'NAME' to the snapshot output. | |
| 132 | ||
| 133 | ||
| 134 | include::common-cmd-help-options.txt[] | |
| 135 | ||
| 136 | ||
| 137 | include::common-cmd-footer.txt[] | |
| 138 | ||
| 139 | ||
| 140 | SEE ALSO | |
| 141 | -------- | |
| 7c1a4458 | 142 | man:lttng(1) |