| 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] |
| 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') |
| 18 | |
| 19 | Remove a snapshot output: |
| 20 | |
| 21 | [verse] |
| 22 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot del-output* [option:--session='SESSION'] |
| 23 | ('ID' | 'NAME') |
| 24 | |
| 25 | List current snapshot outputs: |
| 26 | |
| 27 | [verse] |
| 28 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot list-output* [option:--session='SESSION'] |
| 29 | |
| 30 | Take a snapshot: |
| 31 | |
| 32 | [verse] |
| 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') |
| 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 |
| 49 | time using the man:lttng-create(1) command. |
| 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. |
| 66 | See man:lttng-create(1) to learn more about the URL format. |
| 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 |
| 98 | man:lttng-stop(1)). Otherwise, the snapshot could contain "holes", |
| 99 | the result of the tracers overwriting unconsumed trace packets during |
| 100 | the record operation. After the snapshot is recorded, the tracers can be |
| 101 | started again with `lttng start` (see man:lttng-start(1)). |
| 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 | -------- |
| 142 | man:lttng(1) |